Fondants and Creams

Abstract

Fondant is a partially crystalline (and therefore, also partially liquid) confectionery ingredient with numerous small sugar crystals held together by a saturated sugar syrup. It is one of the oldest forms of confections. Possibly the earliest version of a fondant-type product is crystallized honey , where a portion of the glucose found in honey was crystallized into numerous small particles. The high crystalline content of fondant imparts a solid-like characteristic dependent on the nature of the crystal dispersion.

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1 Introduction

Fondant is a partially crystalline (and therefore, also partially liquid) confectionery ingredient with numerous small sugar crystals held together by a saturated sugar syrup. It is one of the oldest forms of confections. Possibly the earliest version of a fondant-type product is crystallized honey , where a portion of the glucose found in honey was crystallized into numerous small particles. The high crystalline content of fondant imparts a solid-like characteristic dependent on the nature of the crystal dispersion.

Typically water content in fondant may be in the range of 10–15%, although slightly lower or higher values may sometimes be found. Water is one of the most important components since it affects the hardness of the fondant, with higher water content giving a softer and runnier fondant. A softer fondant can also be produced by addition of crystallization modifiers like corn syrup, invert sugar, glycerol or sorbitol. These components contribute to the liquid phase, increasing the dissolved solids in the syrup phase and decreasing the amount of sugar crystals in the fondant.

Approximately 45–60% of the mass of fondant is in the form of small sugar crystals, which are held together by a solution phase that contains all the water and various dissolved sugars (sucrose, corn syrup, other texture modifiers, etc.). Product characteristics are determined by the relative amounts of crystalline and solution phases, the concentration of the solution phase, and the nature of the crystalline dispersion (e.g., crystal size distribution). In a good fondant, the sucrose crystals cannot be detected in the mouth because they are all smaller than some threshold detection limit (typically given as about 20 μm). Thus, controlling sugar crystallization is key to ensuring a high quality fondant product.

Fondant is used in a variety of confections and confectionery applications . It is most often used as the base material to make cream candies coated in chocolate. Fondant is also used as the starting point for other products, like frosting and icing for use on baked goods, and is often used itself as a coating or icing for cakes and other pastries. Fondant is also used to seed crystallization in confections like fudge or chewy candies. Seeding with fondant helps control formation of the proper size and dispersion of sugar crystals in these products, characteristics that are important to their overall quality.

Creams (sometimes called crèmes) are typically, but not exclusively, differentiated from fondant by the addition of frappé, an aerated sugar product. The numerous small air bubbles in frappé , which resembles a highly aerated marshmallow, decrease density and give creams a lighter texture than fondant. Creams also generally contain colors and flavorings , along with some invertase to provide softening over time.

Cream candies may either be cast in molds or extruded and cut. Cast creams are made by warming fondant with a thinning syrup (often called “bob” syrup) to a fluid state, adding frappé, flavorings and any other ingredients. Cast creams are formed by depositing the fluid cream into a mold that has the desired candy shape. Either starch or starchless molding (Section 9.3.3.1) can be used to form cast creams. One-shot depositing technology (see Section 15.6.1) may be used to form a cream within a chocolate coating through controlled depositing of both cream center and chocolate outer at the same time. Extruded creams, or cream pastes, may be made from hard fondant at low water content softened by invertase, but more often are made by mixing powdered icing or fondant sugar with a syrup binder to form a dough or paste. The dough is then either rolled and stamped into the desired shapes or extruded and cut to form the pieces.

Creams vary in consistency from soft and runny to firm and hard, depending mostly on water content and use of humectants. A hard cream center can be softened through use of the enzyme invertase in a process often called cordialization due to its use in making Cordial Cherries. Details of this process are covered in Section 9.4.2.

2 Formulations and Ingredients

Fondant is a relatively simple confection, composed primarily of sucrose, glucose syrup and water. Other ingredients, like invert sugar or polyols, may be added to moderate texture and shelf life. Colors and flavors are added to suit. Frappé, a whipped sugar/glucose syrup product, is added to creams to reduce density and provide a lighter texture. At times, the enzyme invertase is added to either fondants or creams to promote softening over time (see Section 9.4.2). Typical formulations for fondants and creams are shown in Tables 9.1, 9.2, and 9.3.

Table 9.1 Typical batch formulations (in %) for fondants

Table 9.2 Typical batch formulation (in %) for cast (deposited) cream

Table 9.3 Typical batch formulation (in %) for extruded (roll) cream

2.1 Crystalline Sweetener

The primary sweetener in fondants and creams provides the bulk (typically 70–90%) of the candy mass. Numerous small sweetener crystals are dispersed throughout the candy, while some of the sweetener is also dissolved (to saturation) in the liquid phase. For fondants made by crystallizing the sweetener, two key criteria are the ease of crystallization and the saturation concentration. Sucrose is the traditional sugar used for crystallizing fondant since it has high solubility and crystallizes readily. Use of glucose or fructose as the crystallizing sweetener in fondants and creams is limited since their crystallization rates are too slow. In sugar-free products, maltitol and isomalt are often used as the crystallizing sweetener. In extruded creams, almost any fine powdered sweetener (sucrose, glucose, fructose, maltitol, isomalt, etc.) may be used since crystallization during processing is not necessary .

2.2 Doctoring Agent/Crystallization Control Additive

Sucrose alone would not make an acceptable crystallized fondant since too much crystallization would occur – the result would be a hard, crumbly mass of sugar. Typically, glucose syrup is added to fondant (10% is common, but may be up to about 30%) to moderate sucrose crystallization and thereby, control texture. The ratio of sucrose to glucose syrup in fondant determines the amount of sucrose crystallinity and thus, significantly affects fondant texture. Fondant made with high sucrose to glucose syrup ratio has high crystalline content and low dissolved solids in the aqueous phase, resulting in a firmer, more brittle fondant than one made with higher glucose syrup content. Increased glucose syrup level also influences shelf stability since the lower molecular weight sugars in glucose syrup give a lower water activity (compared to sucrose) for given water content, which can protect against mold growth. Moisture loss during storage is also reduced with use of more glucose syrup in the formulation. Invert sugar has similar effect as glucose syrup in controlling sucrose crystallization, but has even greater effect on moisture (and so falls under the category of humectant).

Traditionally, 42 DE glucose syrup is used in fondant manufacture to control sucrose crystallization and moderate fondant texture. Glucose syrup also moderates fondant water activity since the glucose syrup solids are retained in the liquid phase of the fondant, raising its concentration. Use of a lower DE glucose syrup gives a harder and more viscous fondant, since the liquid phase has a higher viscosity. In contrast, use of a higher DE glucose syrup (or high fructose corn syrup) gives a softer fondant since the liquid phase is less viscous, but it would also be more hygroscopic. Use of a high DE glucose syrup moderates sucrose crystallization, but also provides humectant properties (see next section).

In sugar-free fondants , hydrogenated starch hydrolysates (or maltitol syrups) are often used in the same way as glucose syrup is used in sugar-based fondants. The diverse molecular nature of maltitol syrups (the wide range of molecular weight polyols) helps inhibit crystallization of the primary sweetener (isomalt, maltitol, lactitol, etc.) .

2.3 Humectants, Texture and Shelf Life Enhancers

Sometimes other ingredients are added to provide specific enhancements. For example, humectants such as invert sugar, sorbitol and glycerol may be used (at up to a few percent) to modify texture and storage properties. Humectants, defined as materials that promote retention of water, give a more tender texture to fondant, in part by decreasing crystallinity in the same way as glucose syrup (see Section 9.2.2), but also by causing a substantial decrease in water activity. The reduced water activity helps protect against mold growth and moisture loss of the final product. Besides their humectant properties, texture enhancers also soften the fondant by reducing the viscosity of the liquid phase .

2.4 Flavors

The choice of flavor in a fondant or cream is based on the desired effect, and a wide range of flavored products is available. Mint is often a highly desired flavoring in fondants and creams since mint flavors are sufficiently strong to offset the sweetness of the high sugar content. The “cooling” sensation of mint flavors, especially in the center of chocolate-covered creams, can also offset the sweetness and extend the flavor sensation. Other various flavors also can be found in cream centers, from maple syrup to cherry cordial.

Typically, liquid flavors are added late in the process to minimize flavor degradation during heating. For example, flavor may be blended into the fluid fondant (e.g., in an in-line mixer or separate mixing tube) after it exits the fondant beater, just prior to cooling and solidification. The liquid flavors are usually water soluble and dilute enough to be totally dissolved into the fondant or cream matrix. Oil-soluble flavors may be used in creams with higher fat content to ensure the flavor is more fully incorporated into the cream. In the case of fruit flavors (citrus, berry, etc.), a slight amount of acid is often added to the fluid fondant to increase the flavor impact and enhance the nuances of the flavor. As always, flavors need to be stored properly prior to use in order to provide fresh flavor for enhanced shelf life of the fondant or cream.

Natural flavors (fruit purees, etc.) are often used at slightly higher levels than synthetic flavors. These ingredients also provide coloring to creams .

2.5 Colors

Both artificial and natural (exempt from certification) colors may be used to provide distinctive fondants and creams. Because of the relatively higher water content, either certified dyes or lakes may be used. Water-soluble natural pigments would also find application in creams.

Colors based in sugar syrups (solutions or dispersions) can be helpful so as not to lower the solids of the candy significantly as well as making it easier to mix into the fondant and creams. Dark colors are difficult to achieve with the whiteness of the crystalline material. When dyes are used, any migration or change in moisture can cause mottling. Many exempt “Natural” colors tend to function as dyes so the cautions apply to them as well. Caramel colors used at moderate to high levels can impart additional stickiness and should be used with care. Slight changes in base formulation can sometimes counteract higher liquid caramel levels.

Other ingredients that are normally added for flavor can impart color as well. They are not classified as colors, but can help differentiate flavors. Freeze or roller dried fruit powders, cocoa/cacao mass, instant coffee, roasted nut pastes, and maple/brown sugar can all impart color to fondant and creams .

2.6 Frappé

Frappé , a whipped sugar foam, is a key component to a good cream since it lightens the texture of a dense fondant. Frappé is made by whipping sugars (glucose syrup and sometimes sucrose) together with a protein stabilizer (egg whites, soy proteins and/or gelatin) to make an aerated product similar to marshmallow (see Chapter 11). Typically, frappé is aerated until it becomes a thick foam, with a density between 0.35 and 0.5. A good frappé has numerous small air cells held firmly by the protein to retain air when it is blended into the fondant. The air bubbles in frappé also provide a whiter, more opaque characteristic to the cream .

2.7 Fats

In some creams, particularly butter creams, it is desirable to have a small amount of fat, perhaps up to 7–8% of the total product weight. The fat provides lubricity in the mouth and a specific flavor release associated with lipid-based flavors. In buttercreams, real butter is most often desired for the natural flavor; however, hardened vegetable fats are often used with appropriate flavorings to reduce costs.

Since lipids reduce aeration and whipping efficiency, any fats or lipid-based flavors must be added carefully at the end of the process so as to minimize deaeration of the frappé .

2.8 Preservatives

No microbial growth will occur in fondants and creams if they are formulated correctly, with water activity of the liquid phase below about 0.65. At times, chemical preservatives like sorbic acid or potassium sorbate may be added to inhibit mold growth when the water activity is higher .

2.9 Invertase

The enzyme invertase is often added to fondants and creams to provide a softening effect during storage. Incorporating invertase into a fondant or cream formulation converts an initially hard product, one that can be enrobed or panned, into a softer product during storage. The level of invertase added (0.1–0.3%), the water content of the cream, and the nature of the sweetener phase determines the ultimate end point of softening. More details about invertase activity are given in Section 9.4.2. The action of invertase causes a decrease in water activity, thereby extending shelf life .

3 Manufacturing

The manufacturing steps for making fondants and creams depend on the size of the operation and the nature of the product being made. Fondants and creams can be made either in small batches or in high-capacity continuous processes. Fondants and creams also can be made either by crystallizing the sugars within the batch or by adding water to a powdered fondant sugar. The general steps in production of fondant by the crystallization process are shown in Figure 9.1.

Figure 9.1

Typical process schematic for making fondant

Small candy makers generally make fondants and creams in batch cookers. The sugar and water are weighed out and heated in a kettle, and once the sugar is completely dissolved, the glucose syrup is added. Heating continues as the batch begins to boil and temperature increases. Once the desired boiling point temperature (indicative of the final water content) is reached, the batch is carefully poured into a mixing vessel (like a cream beater) and allowed to cool undisturbed. After cooling to the appropriate beating temperature, the mixer is turned on and crystallization is induced by the agitation of the beater. For cast creams, thinning syrup, colors, flavors and frappé are added, as desired, to the fondant, the mixture is warmed carefully to reach the desired fluidity for depositing, and the fluid mixture is deposited into molds (starch or starchless) for cooling and solidification.

Large candy makers use a continuous process for making fondant and cream. Liquid sugar (67% solids) and glucose syrup are mixed and immediately cooked to the desired temperature (water content). The cooked mass is cooled statically (no agitation) to the proper beating temperature (for example, on a cooling wheel), at which point intense agitation is applied to generate massive nucleation of sugar crystals. Additional ingredients like colors, flavors and frappé may be added at this point, usually in-line, while the fondant is still warm and somewhat fluid. If the fondant is to be stored for later use, it is collected and cooled. If the fondant is to be used immediately for making creams, it is sent for appropriate subsequent processing to create the final product.

3.1 Fondant

Producing fondant by crystallization requires several steps: (1) preparation of a sugar syrup, (2) concentrating that syrup to the appropriate water content, (3) cooling it to the desired beating temperature, and (4) massive agitation to crystallize the fondant. The resulting product has semi-solid characteristics dependent on the nature of sweeteners used and the final water content. Figure 9.2 documents how the steps in the fondant-making process are visualized on the state diagram (see Section 2.10).

Figure 9.2

Sequence of process steps in fondant making depicted on the state diagram for a mixture of 90% sucrose and 10% 42 DE glucose syrup solids (With permission from Hartel et al. 2011)

3.1.1 Syrup Preparation and Concentration

The essential ingredients in the starting formulation for many fondants are sugar, glucose syrup and water. Sufficient water (typically 20% of batch weight) is added to completely dissolve the granulated sugar. Since excess water added at this point has to be boiled off, only the minimal amount of water needed to dissolve the sugar should be added. To ensure that all sugar crystals are dissolved prior to cooking, some manufacturers add the glucose syrup after all the granulated sugar has been dissolved. Sometimes, a pressure dissolver can be used to reduce the amount of water needed and to speed up the syrup preparation step. Dissolution in a pressure dissolver is faster than in atmospheric dissolution because the water is retained in liquid form at higher temperatures to promote dissolution.

The sugar syrup is then cooked to the specified temperature to give the desired water content. The relationship between boiling temperature and water content is given for the specific mix composition (sugar and glucose syrup). Cook temperature may be compensated for fluctuations in atmospheric temperature to ensure the correct water content is attained (see Section 2.7 for further details). Normal atmospheric pressure fluctuations can lead to as much as half a percent difference in water content from the highest high pressures to the lowest low pressures. Cook temperatures must also be adjusted for manufacturing at higher elevations .

To promote rapid evaporation of water from the syrup and to quickly reach boiling point temperature, the choice of cooking unit is critical. If heating is slow, crystallization can potentially occur during cooking when the boiling point curve exceeds the solubility curve (see Section 2.9.1). Batch cooking must be sufficiently fast and the formulation must contain sufficient glucose syrup to avoid crystallization. When cooking a small batch of fondant, a candy manufacturer often uses a wet brush to wipe down the surface of the kettle where boiling is taking place since this is the most likely spot for grain formation. Even though the small amount of water added during this wiping action must be boiled off again, the extra water is critical to redissolve any crystals that form in the kettle prior to cooling and beating.

In continuous operations, rapid evaporation methods, with high rates of heat and mass transfer, are used for cooking fondant syrups. The concentration of sugar syrups from 70% to 75% dissolved solids to 88–90% dissolved solids can be accomplished in a minute or two. Thin-film evaporators (microfilm cookers) are common for this purpose, as are shell and tube heaters. In a shell and tube heat exchanger, the syrup under pressure flows through a bundle of tubes housed inside a steam chest. Because of the elevated pressure inside the tube bundle, the water in the sugar syrup remains liquid even at temperatures of 115–121 °C (240–250 °F). After reaching the desired temperature, the syrup enters a flash chamber where pressure is reduced suddenly and the water flashes off as steam. The concentrated syrup is collected at the bottom of the flash chamber .

3.1.2 Cooling and Crystallization

Once the sugar syrup has reached the desired moisture content, it must be rapidly yet gently cooled to a temperature where optimal crystallization occurs. If crystallization takes place during cooling, the crystals formed grow significantly larger than those that are formed later in the beating stage. Thus, it is critical that the hot syrup be cooled quickly and without agitation to prevent undesired spontaneous nucleation of the supersaturated syrup.

Numerous methods have been developed to cool the supersaturated sugar syrup quickly. Probably the simplest cooling method is to pour the hot liquid onto a cold table or surface. For hand beating of fondant, a cold table with controlled temperature (via water circulation) would be used.

In small-scale operations , fondant is still made in batches on a cream beater (Figure 9.3). The hot fondant sugar syrup is poured onto a flat circular platform cooled from below with circulating water. When the sugar syrup cools to the optimal beating temperature, the beater motor is engaged, which causes a series of plows to rotate, scraping the syrup off the platform and distributing it around and behind the plows. This agitation is sufficient to induce crystallization over a period of 20–30 min. Since this process is generally open to the surrounding air, crystallization on a cream beater often leads to a slight loss of water (1–2%) to the environment. This water loss must be offset by cooking to a lower temperature to give a slightly higher initial water content.

Figure 9.3

Cream beater (Courtesy of Savage Bros.)

A common cooling technology for larger-scale operations is a refrigerated cooling drum . The syrup is applied in a relatively thin (5 mm) layer to the top of a slowly turning drum with refrigerated water circulating within the drum to provide cooling (Figure 9.4). The drum turns slowly (about 1 RPM) to allow adequate time for the syrup mass to cool sufficiently before it is scraped off. Near the bottom of the drum, a scraper blade removes the cooled amorphous syrup and deposits it into the hopper that feeds the beating tube. The amount of syrup loaded onto the drum and the RPM of the drum are matched to the desired production capacity so that the syrup entering the beating tube has cooled to the proper temperature by the time it reaches the scraper blade. In order to ensure that no crystals are formed on the cooling drum after the cooled layer is scraped off, the surface of the drum at this point is cleaned with a spray of steam. This ensures that fresh cooked syrup applied at the top of the drum rotation falls onto clean (without crystals) metal surface. Without this cleaning step, a crystallized layer would eventually form on the drum surface, seeding the supersaturated sugar syrup and leading to uncontrolled crystallization .

Figure 9.4

Cooling drum for fondant showing syrup distributor at the top of the drum (Courtesy of Lawrence Foods)

Once the syrup has cooled to about 45–50 °C (114–122 °F), it is ready for intense agitation to promote spontaneous crystallization. At this temperature, the sugar mass is at the optimal supersaturation to promote the maximal rate and extent of crystallization (see Section 2.11.2). Intense mixing at this point is desired to promote formation of numerous small sugar crystals that give the desired smooth texture. If temperature is too high in the beating stage, the lower supersaturation means fewer crystals are formed. Likewise, if temperature is too low in the beating stage, the viscosity is too high and again fewer crystals are formed. In both cases, the end result is larger mean crystal size and coarser fondant. It is critical that the beating temperature be kept at the optimal point to ensure the finest sugar crystals and smoothest fondant.

Continuous fondant beaters are typically cylindrical-shaped mixers with blades that turn on a central shaft with stationary pins to provide intense shearing (Figure 9.5a). The agitation rate of the beaters is about 100 RPM, with a residence time of about 6 min in the beating tube. Clear syrup enters one end of the beating tube (Figure 9.5b) and fully crystallized fondant exits. The massive crystallization that takes place in the fondant beater tube relieves the supersaturation of the sugar syrup almost instantaneously, meaning that billions of crystals are formed in a very short time period. Because so many crystals are formed, they all remain quite small since there is only a certain amount of crystalline mass to spread among the myriad crystals. The massive crystallization also causes a temperature increase of a few degrees due to the release of latent heat. To offset this heat input due to crystallization, cooling water is usually circulated through the jacket of the beater tube to maintain desired temperature.

Figure 9.5

Opened continuous fondant beating tube : (a) empty tube, (b) stop flow during operation showing progression of fondant graining from top to bottom (Courtesy of R. Hohberger, SPEC Engineering)

The product exiting the beating tube is still somewhat fluid so it can be pumped. This is in part because it is still warm, but also because crystallization has not been quite completed yet by the time it exits the beating tube. Thus, it retains some fluidity despite the large amount of crystalline material. From here, fondant either goes to packaging for later use or undergoes further processing steps (i.e., ingredient addition, cream production, etc.).

3.1.3 Packaging

Since fondant is often used as an ingredient in other manufacturing processes (i.e., creams, icing, frosting, etc.), it can be collected and stored for later use. Typically, pails or boxes are filled with fluid fondant as it exits the mixer, which are then allowed to cool as the fondant continues to crystallize for subsequent storage and distribution. Cubes of fondant weighing 22.7 kg (50 lb) are common for distribution .

3.1.4 Ingredient Addition

If the fondant exiting the beating tube is to be used directly, usually additional ingredients need to be added. Since the fondant is still sufficiently fluid as it exits the beating tube, this provides an ideal point for addition of other ingredients. Colors, flavors and frappé (for creams) may be added into the fluid fondant by mixing in a second beating cylinder (Figure 9.1). The agitation in this mixer (50–60 RPM) is not as intense as in the fondant beating tube, but is sufficient to completely incorporate these other ingredients within the residence time (≈6 min) so that the product exiting the second tube is completely mixed. This product may be packed and stored for later distribution or may be pumped directly to the next stage for processing .

3.2 Powdered Fondant

Dried fondant sugar (or icing sugar) is also produced for certain applications, particularly for icings and extruded cream pastes. Fondant sugar is usually produced by micropulverization. Refined sugar is ground with 2.5–10% glucose syrup solids, maltodextrins or other low DE (dextrose equivalent) cereal products as a flow aid to help improve flowability of the powder, to control moisture, and provide enhanced dispersion in water. In the ground powder, 99% of the particles are less than 44 μm in size (pass through a US Number 325 mesh sieve). Powdered fondant can also be made by crystallization in an extruder, followed by grinding and sieving .

3.3 Creams

Fondants are typically used as the starting point for making creams. Deposited, or cast , creams are made by melting fondant in a bob syrup prior to depositing into a mold, whereas extruded creams are typically made by forming a paste from fondant sugar powder. Many cream candies are coated in chocolate after solidification, either by shell molding (see Section 15.6.1), enrobing through a curtain of chocolate (see Section 15.6.2) or by a panning process where a chocolate shell is applied by sequential applications of liquid chocolate (see Chapter 17).

3.3.1 Deposited (Cast) Cream

The general process for making cast creams is shown in Figure 9.6. To prepare a cast cream, fondant is diluted with thinning syrup and frappé is added to provide a lighter texture. A typical formulation for deposited cream is given in Table 9.2. A typical cream has about 40–45% fondant, 10–25% frappé and 34–38% thinning syrup, depending on the desired fluidity and hardness of the cream product. Colors and flavors are added to suit the product needs. The semi-fluid product is then deposited into molds to form the final shapes, which are cooled and allowed to set prior to subsequent use (e.g., chocolate enrobing).

Figure 9.6

Typical process schematic for making deposited cream

Frappé is made by whipping glucose syrup (sometimes with sucrose) in the presence of a protein stabilizer (egg albumen, gelatin, etc.) to a specific gravity of between 0.3 and 0.4. Whipping frappé is accomplished in a high-speed whisk, either at atmospheric pressure or at elevated pressures. In a pressurized whisk, a specified amount of air is incorporated into a known amount of syrup to produce a frappé with specific density. Either air or an inert gas like nitrogen can be whipped in a pressure whisk .

Thinning syrup (sometimes called “ bob” syrup) is made of dissolved sucrose, glucose syrup and sometimes invert sugar. A typical composition of thinning syrup is about 3 parts granulated sucrose, 1.6 parts glucose syrup (usually 42 DE) and perhaps 0.8 parts invert sugar, cooked to about 117 °C (242 °F) to reduce water content to about 11 or 12%. Ideally, addition of thinning syrup does not cause dissolution of any of the small crystals in fondant, it just dilutes the crystals by adding a syrup with the same composition (sucrose, glucose syrup solids and water content) as the liquid phase of the fondant. This disperses the crystals in the fondant and provides sufficient fluidity to allow molding. In principle, the composition of the thinning syrup should match the saccharide composition of the continuous phase of the fondant. However, since the thinning syrup is warm, some of the sugar crystals in the original fondant are dissolved due to the higher solubility at the higher temperature (see Section 2.8). Thus, the process of adding thinning syrup is often called remelting (although technically it probably should be called redissolving). The result of adding warm thinning syrup to prepared fondant is to thin out the fondant so that it can be used for forming and molding. The reduced viscosity, due to warmer temperatures, reduced crystalline sugar content and increased liquid phase, allows the fondant to be poured into molds and formed into desired shapes.

Even when the thinning process is done carefully, the sugar crystals in the finished cream do not return to exactly the same state (number and size) of the original fondant upon cooling. When the thinned fondant cream is cooled, additional sugar crystallizes out of the solution onto the remaining sugar crystals. Crystallization continues until phase equilibrium is attained, meaning the sugar molecules in the solution (liquid) phase have reached equilibrium with the sugar molecules in the crystalline (solid) state. However, since some of the original sugar crystals in the prepared fondant were dissolved away, there are fewer crystals in the remelted fondant and when cooled to the same temperature, each of the remaining crystals must grow a little larger to accommodate the recrystallized mass. Thus, remelted fondant typically has a slightly larger mean size than the original fondant, which may result in the cream being perceived as slightly coarse. Great care is needed when remelting fondant to make deposited creams – the lowest temperatures that still give the desired fluidity are recommended. Temperatures above about 80–82 °C (175–180 °F) are not recommended.

The fluid creams made by thinning fondant and adding frappé are deposited into molds and allowed to set into the desired form. Depositing of fondant and cream candies is done in either candy-shaped depressions formed in molding starch (starch mogul ) or in pre-shaped plastic molds (starchless molding).

3.3.1.1 Starch Molding

In starch molding of cast creams, the thinned liquid cream is deposited into impressions in a tray of dry powdered starch (usually corn starch) and allowed to solidify. Imprints of the desired shape are pressed into a layer of starch prepared in a starch board. The starch is usually treated with a small amount of oil (mineral or vegetable) to help shape retention and reduce dusting. Water content of the starch should be within 5–7% in order to provide proper drying of the cream during curing. The liquid cream is deposited through a nozzle to fill the imprints in each board. The temperature and water content of the deposited cream must be carefully controlled so that the viscosity of the fluid cream is sufficiently low that it completely flows into all details of the impression to give the desired shape. Temperatures of 65–71 °C (150–160 °F) are common for the depositing cream. Typically, the water content of the fluid cream being deposited is 1 or 2% higher than the final desired water content of the cast cream since the cream loses water to the starch during curing.

Filled trays are held, or cured, overnight to allow the creams to solidify and lose moisture. Curing takes between 3 and 24 h at temperatures of 24–27 °C (75–80 °F) and 50–60% RH. After solidification, the starch trays are upended and the candy pieces separated from starch on a screen. The separated candies remaining on the screen proceed to the next step in the operation, while the starch, which passes through the screen, is dried and reused in the starch mogul .

Some deposited cream candies, such as candy corn, require sequential depositing steps to build the different colored layers. In candy corn, three sequential cream deposits, first the white, next the orange, and finally the yellow, are deposited into a corn kernel shaped mold. Timing of each deposit is critical to ensure that each of the three layers adheres properly to the other layers.

Additional details of starch depositing and starch mogul operation can be found in Section 12.3.2.2.1.

3.3.1.2 Starchless Molding

Because starch molding is time consuming and creates a hazardous, dusty environment in the plant, cast creams may often be deposited into molds made of rubber (or some other flexible material). The main advantage of starchless molding is that process times can be shortened considerably, compared to starch molding, by elimination of the curing step. However, some differences in formulation are usually necessary since there is no moisture loss during setting.

Solidification of cast creams in rubber molds occurs solely by cooling, rather than by a combination of cooling and drying. Therefore, the liquid cream must be close to the final desired water content when it is deposited. The lower water content for creams cast in rubber molds means that the viscosity of the fluid cream is higher than the viscosity usually used for molding into starch. The higher viscosity may limit certain applications where intricate designs are required. However, the main disadvantage of starchless molding is the lack of flexibility to change shapes since it can be quite time consuming to change molds in the depositing machine. Typically, starchless molding is most useful for large quantity production runs of a single product shape.

In starchless molding, solidification times are generally short enough that cooling tunnels can be used to set the creams. Often, a continuous conveyor operation is used. Empty molds enter the depositing section and are filled with liquid cream. The filled molds exit the depositing section and immediately enter the cooling tunnel, where conditions of temperature and airflow are matched with the residence time in the tunnel (20–30 min) such that the creams have solidified sufficiently upon exit from the tunnel. Within the tunnel, the creams cool, solidify and shrink slightly as sugar crystallization occurs. The molds are turned upside down to remove the candy creams, sometimes assisted by stretching the molds to apply torque to help the creams come out. If necessary, the molds are cleaned before they re-enter the depositing section of the machine for another round of depositing candies. In general, starchless molding requires moisture contents of 12% or less. Higher moisture content causes the cream centers to stick to the mold and cause problems with operation.

3.3.1.3 Chocolate Molding

To make cream-filled chocolate, either hollow-shell molding (see Section 15.6.1) or single-shot depositing (see Section 15.6.1) are most often used. In hollow-shell molding, tempered chocolate is deposited into a mold, the mold is overturned and liquid chocolate shaken out, leaving a shell of chocolate lining the mold shape. After cooling to solidify the chocolate, cooled cream is deposited into the mold, taking care not to overfill the form. The temperature of the cream must be sufficiently low that the chocolate shell is not melted. A layer of tempered chocolate is then applied to the top of the cream-filled mold and the excess chocolate scraped off. The chocolate bottom fuses with the chocolate shell to provide a complete encasing of the cream. After cooling, the molds are over-turned to release the cream-filled chocolates for subsequent packaging.

Fondants and creams may also be deposited into molds along with a chocolate coating in single-shot depositing technology. Here, dual nozzles are used with chocolate applied through the outer nozzle and cream paste applied through the inner nozzle (see Section 15.4.11.1). Pump actuators are carefully synchronized to initiate the chocolate flow into the mold an instant before the center cream filling is initiated. This allows a chocolate layer to form first along the mold surface. The cream paste pump is stopped an instant before the chocolate pump is stopped to allow a complete chocolate coating surrounding the cream paste. When done correctly, the entire operation of depositing a chocolate-coated cream center piece can be done in a single step. It is imperative that viscosities of both cream center and chocolate exterior are carefully controlled for proper single-shot operation. Temperature, water content and crystalline content of the cream paste are critical parameters that must be controlled to attain the desired viscosity. If not properly synchronized, uneven chocolate coatings can be formed. In extreme cases, improperly sealed pieces can be formed that subsequently leak filling.

3.3.2 Extruded Cream

An extruded cream piece can be made by mixing powdered fondant with sufficient water to make a paste (with a dough-like consistency) and then forming the pieces by extruding the paste through specially-designed nozzles or dies. A typical process for making extruded creams is shown schematically in Figure 9.7. A typical formulation for an extruded cream is given in Table 9.3.

Figure 9.7

Typical process schematic for making extruded cream

The principle ingredients are powdered fondant, or icing sugar, and water. When water is added to the powdered fondant sugar, some of the sucrose crystals dissolve until the water becomes saturated with sucrose. At this point, the physical properties of the mixture depend on the relative level of water added to the dry fondant powder. At about 8–10% water, the mixture takes on the consistency of a very firm paste. With more water added, more sugar crystals dissolve and the fondant becomes thinner and may even flow. Generally, conditions that give a pliable paste or dough are desired since this consistency can be easily extruded and formed into the desired shape, but still sufficiently firm to maintain its shape for subsequent processing.

Other ingredients that may be added to enhance extruded creams include melted butter or vegetable fat (4–8%) to make a buttercream, colors and flavors to suit, and the enzyme invertase (0.1–0.3%) to promote softening during storage (see Section 9.4.2).

Once the paste is made, individual pieces are often formed by extrusion. In the extrusion process, the paste is forced through a die with the desired shape and cut into individual pieces by a knife or wire passing across the die face. Alternatively, the creams can be deposited directly onto a belt into the desired shape. The individual pieces are collected on a conveyor, cooled to solidify the piece, and taken for further processing (usually enrobing in chocolate). Alternatively, creams can be deposited directly onto a chocolate wafer, as seen in Figure 9.8, which eliminates the need to pre-bottom the cream before enrobing.

Figure 9.8

Depositing cream onto a chocolate wafer (Courtesy of Hacos)

4 Product Characteristics

Many factors affect the quality of fondants and creams, but none are more critical perhaps than the nature of the sugar crystals. The amount of crystalline material and the size distribution of the crystals govern texture (hardness, flow characteristics, etc.), flavor release, shelf life, and sensory evaluation of smoothness. Thus, control of particle size is one of the most critical control points in fondant production.

The liquid phase also plays an important role in texture and shelf life of fondants and creams, particularly governing water activity and specifically, the ability to support microbial growth. Since a large portion of the sugar is in crystalline form, the dissolved solids concentration of the liquid phase is low (relative to ungrained confections), and this can lead to a sufficiently high water activity to support mold growth. Thus, certain additives, like corn syrups and other humectants, are important additions to the formulation to control water activity (and texture). The use of invertase in creams provides an additional level of control of texture and quality.

4.1 Microstructure and Product Properties

Fondant is a highly crystallized dispersion , with numerous, small sugar crystals distributed within a liquid matrix. A cream is similar in structure, although it also contains small air bubbles from the addition of frappé. The relative ratio of crystalline phase to liquid phase, the nature of the crystalline dispersion, and the composition of the liquid phase are important factors governing the texture, quality and shelf life of fondants and creams.

Numerous factors influence the rate and extent of crystallization during manufacture of fondant (Lees 1965; Hartel 2001).

• Supersaturation : The driving force for crystallization, supersaturation, is a function of syrup concentration, composition and temperature (see Section 2.10). Higher supersaturation promotes more rapid crystallization, up to the point where molecular mobility is impeded as viscosity increases.

• Beating temperature : As seen in Figure 9.1, the sugar mass must be cooled to the temperature at which nucleation rate is highest to generate the largest number of crystals.

• Beating intensity : Crystallization is enhanced by rapid and intense agitation.

• Presence of crystallization inhibitors : Various ingredients added to fondant (e.g., invert sugar, glucose syrup, etc.) are known to inhibit crystallization rate and decrease the crystalline phase volume in fondant. In part, this effect comes from a combination of specific inhibition of crystallization and modification of the phase diagram (see Section 2.8).

In turn, the crystallization process determines the nature of the crystalline phase, which then affects the texture and sensory properties of the fondant.

• Crystal size distribution : In a smooth, creamy fondant, crystal sizes range from as small as a micron or so to 15 μm. Mean crystal size should remain below 15 μm with only a few crystals above 20 μm.

• Crystal content: Arguably, the most important determinant of fondant texture is the amount of crystalline material, or rather, the ratio of crystalline to liquid phases. As crystal content increases, hardness of fondant increases accordingly.

• Liquid phase : As crystal content goes up, the liquid phase decreases proportionally. Beyond the amount of liquid phase, its composition also has significant influence on fondant quality. In particular, water activity of the liquid phase governs the water activity of the fondant (crystals do not contribute to water activity, so in principle the water activity of the liquid phase is what is measured for fondant).

Although many of these topics have been mentioned in previous sections, the principles that govern these effects are discussed here in more detail.

4.1.1 Crystalline and Liquid Phases

In a normal fondant, somewhere between 45% and 60% of the mass is made up of very small sugar crystals, with the rest of the mass in the liquid phase. The exact amount of crystalline sugar is important because higher crystal content leads to a firmer fondant (and vice versa). The liquid phase of fondant contains all the water in the fondant (no water is contained within the sugar crystals) plus dissolved sugars (sucrose, glucose syrup, invert sugar, etc.). Phase equilibration in fondant, which may take several days to achieve, means that the maximum amount of crystals is produced and the solution phase concentration is at the saturation concentration at storage temperature. Thermodynamically, phase equilibrium means that the sucrose molecules in the crystals have the same chemical potential as the sucrose molecules dissolved in the aqueous phase. Since the two phases are at equilibrium, the amount of crystalline sugar present in the fondant (or crystalline yield) can be calculated from a mass balance based on the starting concentration of sucrose and the final solubility of sucrose in the solution, which depends on the temperature and the effects of any other additives, like corn syrup or invert sugar.

Fondant gets its solid-like characteristics , to a large extent, from the high crystalline phase volume. That is, the number of sugar crystals and the distribution of their sizes have a major impact on the physical properties of the fondant. The relative distribution of crystalline to liquid phases is the main factor influencing the physical properties of fondant. In general, the higher the ratio of solid to liquid (crystalline phase volume), the firmer (harder, denser, etc.) is the fondant. Formulations with high levels of sucrose (lower corn syrup) and low water contents lead to hard fondants because of the increased sugar crystal phase volume. Formulations with higher levels of glucose syrup (or invert sugar) and cooked to lower temperatures (higher water content) give softer fondants.

The liquid phase contains all of the water in the fondant as well as dissolved sugars . Any glucose syrup , invert sugar or other dissolved components (e.g., humectants) added to the formulation are found in the liquid phase along with whatever sucrose remains dissolved. The amount of sucrose dissolved in the liquid phase of fondant depends on what other sugars are present in the formulation since sucrose solubility concentration is influenced by the other sugars in the formulation (see Section 2.8).

The water activity of fondant, as measured by the relative water vapor pressure above the fondant, is determined by the liquid phase composition. That is, the crystals in fondant have no effect on water activity of the fondant since they do not contribute to the relative vapor pressure. If a fondant was made with pure sucrose, the concentration of the liquid phase would be 67%, the solubility concentration of sucrose at room temperature. This is true regardless of the final water content of the fondant (see the mass balance equations in Appendix A.9.1). The water activity of a 67% sucrose solution is approximately 0.85 (Norrish 1967), a value where the fondant would be prone to microbial growth. One of the functions of glucose syrup, besides moderating texture of the fondant through control of crystal content, is to decrease the water activity. In the example in Appendix A.9.1 for fondant with 12% water and 70/30 sucrose to 42 DE glucose syrup ratio, the total dissolved concentration in the liquid phase was calculated to be 78%. This is well above the 67% concentration for pure sucrose because the entire amount of glucose syrup solids can be found in the liquid phase. The glucose syrup solids raise the concentration, and also lower the water activity of the liquid phase. In the example in Appendix A.9.1, the water activity of the fondant is approximately 0.78 (based on the Norrish correlation; see Section 3.3.2).

Even with 30% glucose syrup, the water activity of fondant is still considerably above the threshold water activity value at which no microbial growth can occur (0.65). To reduce water activity of fondant even further, additional sugars and humectants can be added, including invert sugar and glycerol. These humectants also impact texture by reducing the amount of crystalline solids, but have a significant effect on reducing water activity since they are small molecular weight sugars.

The nature of the dispersion of the crystalline phase is also critical to the texture and consumer perception of fondant. Figure 9.9 shows a microscope image of typical sugar crystals observed in fondant cream candy. It has been estimated that there are approximately 3.6 × 10¹¹ crystals in every 100 g of fondant mass (Lees 1965). This very large number of crystals with small average size gives fondant its characteristic properties. From a sensory standpoint, the mean size of sugar crystals in fondant should be less than about 10–12 μm. The threshold detection size, or the smallest size that can typically be detected by a consumer, for sugar crystals in fondant is somewhere around 15–20 μm. Crystals much larger than about 20 μm are easily detected by the consumer and impart a coarse texture to the fondant.

Figure 9.9

Sugar crystals in fondant observed by transmission optical microscopy with crossed polarizing lenses. Magnification 40×

Sugar crystal size in fondant can be quantified with any of several different measurement methods, with image analysis of microscope images and laser light scattering being the two most common. Microscope images can be prepared by dispersing the fondant in an organic solvent (e.g., alcohol) that has previously been saturated with sucrose to prevent dissolution. The size distribution of the crystals can be quantified by image analysis of the images. This is a relatively simple method although depending on the resolution of the microscope, very small crystals (less than 1–2 μm) are difficult to quantify. The second method for particle size characterization in fondant is laser light scattering. Here, a dilute dispersion of the fondant in solvent is exposed to laser light and the extinction pattern of the scattered light observed. The size distribution is then calculated from the extinction curve based on light scattering theories. The two methods give slightly different results since they measure different aspects of the crystal dispersion. Microscopy/image analysis measures the projected area of the crystals as they are dispersed on the microscope slide, whereas light scattering measures the volume of particle that scatters the laser light. Furthermore, crystal size can be stated based either on a population basis or a volume (mass) basis, with the two methods giving very different results (see Hartel 2001 for more details). A population-based mean size puts more emphasis on smaller particles, which may be important when there are many more small crystals than large ones. A volume-based mean size , on the other hand, emphasizes the larger particles that carry the larger mass. This may be important when considering the sensory aspects of fondant since only a relatively small number of large particles may be sufficient to cause the fondant to be considered coarse to the consumer. For these reasons, it is important to exercise caution when describing crystal size distributions and to clearly specify which averaging method was used .

To produce the numerous small crystals found in fondant, it is extremely critical to control crystallization. In particular, the nucleation rate (rate of formation of crystals, #/mL-second) must be extremely high in the beating tube. Formulation and processing conditions must be controlled to ensure this rapid rate of nuclei formation to ensure that all crystals remain below the critical threshold detection size.

4.1.2 Parameters That Affect Microstructure

Both thermodynamic and kinetic parameters affect microstructure in fondant. The thermodynamically-governed microstructural characteristics include crystal content, liquid phase content, and liquid phase composition. For a given formulation, these parameters will be the same regardless of the processing conditions, assuming that the system reaches a phase equilibrium (a good assumption for commercial fondant processes).

The primary kinetically-governed characteristic is the sugar crystal size distribution since the span of crystal sizes is controlled by the relative rates of nucleation and growth and the time span over which nucleation occurs (Hartel 2001). Both formulation and processing conditions affect crystal size distribution by influencing crystallization rates.

4.1.2.1 Formulation Effects

Water content in fondant, which typically varies from approximately 8 to as high as 15%, can cause significant differences in physical properties. Fondant with low water content is very solid, to the point of being hard and even brittle, whereas fondant with high water content is soft and runny. These differences are related primarily to the amount of crystalline phase, which imparts the solid-like characteristics. With high water content, more of the sucrose is dissolved in the solution phase so there is less crystalline mass. Although the syrup phase has higher dissolved solids concentration, the lower crystal content results in a softer and runnier fondant. The opposite is true for fondant with low water content. In this case, less water means more of the sucrose is in crystalline form, so the fondant is harder and more solid-like . Table 9.4 shows the effects of water content on crystal content, liquid phase content and liquid phase concentration in fondant equilibrated at room temperature. These are calculated values from the approach detailed in Appendix 9.1.

Table 9.4 Effects of sucrose to glucose syrup (42 DE) ratio (on a solids basis) on crystal content, liquid phase content and liquid phase dissolved solids (calculated) of fondants at different water contents

Glucose syrup content in fondant may vary from as low as 5% to as high as perhaps 30%. When sucrose is replaced by glucose syrup in a fondant formulation, there is less sucrose to crystallize and the crystal content is reduced. However, glucose syrup also affects the solubility concentration of sucrose in water, so the net effect is complex. When higher glucose syrup levels are used, the crystal content in the fondant is decreased but since all the glucose syrup remains in the solution phase, the final dissolved solids concentration of the liquid phase is increased (Table 9.4). This effect, where the mixture of sucrose and glucose syrup at saturation has a higher total solids content than sucrose at saturation, is discussed in more detail in Section 2.8.

Glucose syrup has also been shown to affect crystallization rates of sucrose, with levels over 20–30% glucose syrup significantly decreasing nucleation and growth rates (Hartel 2001). Thus, one would expect glucose syrup also to affect the crystal size distribution in fondant through its combined effects on crystallization rates, saturation concentration, and supersaturation. Table 9.5 compares the approximate sucrose crystal size distribution in fondants made with different glucose syrup levels (Lees 1965). Interestingly, the fondant made with higher glucose syrup actually contained the smaller sized sucrose crystals. Despite the effect of glucose syrup on reducing sucrose nucleation over this range, the higher addition of glucose syrup resulted in smaller crystals. This was most likely due to differences in the amount of crystal mass found in fondants with 10% or 25% glucose syrup. Although there were probably fewer sucrose crystals in the fondant made with 25% glucose syrup (although no data are available for crystal numbers in this study), those crystals ended up being smaller because the crystal content was about 10% lower with the higher glucose syrup level (compared to 10% glucose syrup).

Table 9.5 Effects of glucose syrup (42 DE) addition on crystal content and sucrose crystal size distributions in fondant with 10% moisture content (Data from Lees 1965)

Humectants , like invert sugar, glycerol and sorbitol, also affect crystal content, liquid concentration and crystal size distribution in much the same way as glucose syrup. A similar effect to that of glucose syrup is seen upon addition of invert sugar and glycerol, where there is less sucrose to crystallize. However, with invert sugar and glycerol, the water activity of the liquid phase is reduced considerably, even more than for glucose syrup, due to the presence of low molecular weight compounds. In the case of glycerol, the syrup phase now contains glycerol and less water, so there is also less dissolved sucrose.

4.1.2.2 Manufacturing Effects

The manufacturing of fondant has already been covered in Section 9.3; here, the focus will be on the specific effects of manufacturing on control of fondant microstructure. Proper control of processing conditions is necessary to ensure the smallest size distribution of crystals (Lees 1965). Although formulation factors (water content, glucose solids, other texture enhancers, etc.) can affect the amount of crystalline material, processing parameters only affect the nature of crystallization and thus, influence the distribution of crystal sizes. Specifically, the processing factors that can affect crystallization in fondant include the rate of cooking (boiling off water to reach the final water content), the rate of cooling of the concentrated syrup, the temperature of beating, and agitation rate during beating. Furthermore, if there are any crystals that remain from the dissolver or are formed during evaporation or cooling, prior to the beating tube, these crystals will grow significantly larger than those formed in the beating tube, potentially giving the fondant a coarse texture. Thus, control of processing factors is critical for production of the highest quality fondant with the smallest sugar crystals and smoothest sensory perception .

The rates of evaporation and cooling are important parameters for controlling crystallization in fondant. Once the concentrated syrup exceeds the saturation concentration and becomes supersaturated (see Section 2.8), it is prone to crystallization. To make the finest crystals, however, the entire mass must be cooled to the optimal beating temperature before any crystallization occurs. Thus, there is a critical period of time from when the syrup becomes supersaturated (during the evaporation step and during cooling) to when it enters the beating tube and is crystallized. On Figure 9.2, this period extends from the point where the boiling point elevation curve crosses the sucrose solubility curve to the point where the cooled, concentrated syrup enters the beating tube. This supersaturated syrup must be handled very delicately to prevent premature crystallization during this time period. The glucose syrup in the formulation provides some crystallization inhibition, but the supersaturated syrup must still be handled very gently, with minimum shearing and agitation, during cooling and transport to the beating tube . Thin-film evaporators and cooling drums satisfy the rapid heating and cooling requirement so that a completely uncrystallized, yet highly supersaturated syrup, is delivered to the beating tube.

One of the most critical control points in processing fondant is the temperature at which it is beaten to induce sugar crystallization. The goal in fondant manufacture is to make as many crystals as possible by promoting the highest nucleation rate. There is an optimal temperature range for supersaturated sucrose syrup that provides this maximum nucleation, where the greatest numbers of crystals are formed (see Section 2.11). Temperatures both higher and lower result in lower rates of nucleation. This optimal temperature point (or range of temperatures) occurs due to a balance between two effects. First, as temperature of the uncrystallized syrup is decreased, the supersaturation of the solution increases. Thus, temperature must be low to induce high nucleation rates and massive crystallization. However, when temperature is too low, nucleation rate decreases dramatically, despite the greater supersaturation, due to the limited mobility of the sucrose molecules. Although some say this inhibition is due to the increased viscosity at this low temperature, it is actually the inability of sucrose molecules to move that cause the low viscosity and thereby, reduces nucleation rate. The optimal beating temperature range for most fondants falls between 45 and 50 °C (114–122 °F), as seen in Figure 9.10, which depicts the induction time (time needed for nucleation to occur) when concentrated sugar syrup is cooled directly to the indicated temperature. The induction time (and inversely, the rate of nuclei formation) decreases as beating temperature decreases to a minimum in the range of about 45–50 °C, followed by an increase in the induction time at lower temperatures .

Figure 9.10

Time required for onset of sucrose nucleation for sugar syrup (80: 20 sucrose to 42 DE glucose syrup on solids basis; 20% water content). Syrups were cooled quickly from 80 °C to observation temperature with agitation initiated once syrup had reached desired temperature (With permission from Hartel et al. 2011)

Agitation rate during beating (or intensity of beating) also affects the ultimate crystal size distribution (Lees 1965). It is widely recognized that energy input to a supersaturated solution can promote nucleation. Thus, the mechanical agitation during beating helps to promote the highest nucleation rate, leading to the smallest crystals and smoothest fondant. Insufficient agitation results in lower nucleation rate and ultimately, larger mean crystal size .

If any crystals are present in the cooked syrup, the final crystal size distribution will have a population of larger crystals since the ones that form first spend more time in supersaturated conditions and grow largest. Seed crystals may be present from a number of possible causes:

• Insufficient dissolution of crystals during fondant preparation,

• Cooking syrup too slowly,

• Cooling of cooked syrup too slowly,

• Insufficient cleaning of the cooling drum prior to syrup deposition, or.

• Uneven cooling of syrup.

Any crystals present in the syrup prior to beating have the opportunity to grow throughout the process and grow significantly larger than those formed in the beating tube. Thus, it is critical to ensure that all crystals are dissolved prior to cooking and that nucleation occurs only in the beating tube.

4.2 Invertase

The use of invertase to soften fondants and creams, a practice used widely in the industry , allows production of a piece that is sufficiently hard to withstand coating with chocolate by panning or enrobing. Over time, within the package, the invertase acts to reduce the viscosity of the fondant, leaving a softer center within the chocolate coating. Commercially, softening may be slight, as found in many chocolate-covered cream candies, or extensive, as seen in cordial cherry candies.

4.2.1 Enzymatic Hydrolysis

Commercial invertase is extracted from yeast by precipitation with alcohol. The extracted enzyme is mixed in glycol to give a commercial solution with standard activity (ability of the preparation to hydrolyze sucrose under controlled conditions).

Invertase (I) is an enzyme that hydrolyzes one molecule of sucrose (S) into one molecule each of fructose (F) and glucose (G), using up a water molecule (W) from the solution in the process, as shown in the following chemical reaction .

$$ \mathrm{S}+\mathrm{W}\overset{I}{\to}\mathrm{G}+\mathrm{F} $$

As the invertase hydrolyzes the sucrose in the solution phase of a fondant, the concentrations of fructose and glucose in the solution phase increase. Figure 9.11 shows the increase in fructose and glucose content during invertase activity on fondant. Note that the glucose level does not start at zero due to the presence of glucose in the glucose syrup (42 DE glucose syrup was used in this example). The speed of the process is dependent on both formulation and operating parameters, including pH, temperature, invertase concentration, and water content.

Figure 9.11

Increase in glucose and fructose content during invertase activity in fondant with 16.8% initial water content (80:20 sucrose: 42 DE glucose syrup on solids basis) (From Wu 2006)

The acidity of the fondant solution phase can impact invertase activity. Commercial invertase used in the candy industry has an optimum activity at slightly acidic pH, between 4.5 and 5. The rate of inversion decreases as pH increases to 7 and is sufficiently slow at pH values above 7 to be considered negligible. pH below 3.0 can inactivate the invertase, so proper control of pH is necessary. Ethanol can also inactivate invertase. For this reason the use of alcohol and alcohol based flavorings with invertase in creams must be used cautiously. As a matter of ‘best practices,’ it is always wise to add invertase as the last ingredient in confection formulations.

Temperature is another parameter that influences invertase activity. Since invertase is a protein, temperatures above about 80 °C (176 °F) cause rapid denaturation of the enzyme and subsequent loss of activity. For this reason, invertase cannot be added into the batch formulation prior to cooking the sugar syrup; if cooked in the batch, the invertase will completely denature and lose all of its activity. The maximum activity, or rate of inversion, occurs at approximately 63 °C (145 °F); however, even at this warm temperature, there is a substantial loss of activity, on the order of 10% over a period of 30 min. Because of this inactivation at warm temperature, the time a commercial cream spends in the remelting stage can have a significant effect on subsequent activity of the enzyme and can lead to less softening of the product than desired (or expected). Adding invertase as late in the process as possible ensures that the enzyme retains maximum activity .

One of the most important parameters influencing invertase activity is the water content of the liquid phase or the inverse of total solids. More correctly, the water activity governs the ability of the enzyme to operate. Sufficient water must be available for the enzyme to be active. If dissolved solids content increases too much during hydrolysis and water activity decreases too much, invertase activity stops. Numerous studies suggest that invertase activity ceases when water activity decreases to about 0.65 (Silver and Karel 1981; Wu 2006), although the exact value may depend on other parameters (i.e., invertase concentration, glucose content, etc.). Some say the limiting condition is when soluble solids in the liquid phase reaches 83%, but the composition of the liquid phase is important in that it determines water activity. Silver and Karel (1981) showed that invertase activity stopped once water activity had fallen sufficiently, but that the enzyme retained activity once water was added back into the system. That is, the enzyme stops because conditions become unfavorable, not because the enzyme is destroyed. It becomes active again if more water is added.

Since one molecule of water is needed to hydrolyze one molecule of sucrose, which is replaced by one molecule each of fructose and glucose, both water content and water activity decline substantially during invertase activity (Figure 9.12). There is a natural inhibition that governs the maximum extent of the invertase reaction, which means there is a maximum level of softening that can occur for each formulation. The end-point of the reaction is dependent on soluble solids content, water activity, and glucose content (product inhibition).

Figure 9.12

Change in water activity during softening of fondant (80:20 sucrose: 42 DE glucose syrup) at room temperature with different initial moisture content by invertase (From Wu 2006)

4.2.2 Physical Changes Due to Invertase Action

When the invertase hydrolyzes a molecule of sucrose into glucose and fructose, numerous things change in the fondant. The most obvious is the change in concentration of all three sugar molecules, a decrease in sucrose and water concentrations and an increase in fructose and glucose concentrations. In fact, the rate of the inversion reaction can be followed in a fondant by tracking the increase in both glucose and fructose (Figure 9.11). However, several physical properties change as these concentrations change, the sum of which ultimately causes the observed softening.

The removal of a sucrose molecule from the solution and addition of glucose and fructose molecules causes a slight shift in phase equilibrium of sucrose. There now is one less molecule of sucrose in solution, which causes the solution to become slightly undersaturated. This means that a molecule of sucrose can now dissolve from the crystalline phase and become part of the solution. Actually, this is not quite a one to one relationship between sucrose molecules hydrolyzed and sucrose molecules dissolved from the crystal, since the addition of the glucose and fructose to solution causes a slight decrease in the solubility of sucrose (see Section 2.8). Regardless of the exact balance, as more and more sucrose molecules in the solution are hydrolyzed by the invertase, more and more sugar crystals dissolve. At the same time, one molecule of water is removed from solution for each molecule of sucrose that is hydrolyzed.

With the change in crystal content and presence of invert sugar, there is a substantial decrease in viscosity and increase in fluidity of the fondant due to the changes in composition. With a decreased content of crystalline sucrose and increased glucose and fructose concentrations in solution, the entire fondant becomes more fluid in nature, despite the slight decrease in water content. For a given molar concentration, glucose and fructose, both monosaccharides, are less viscous than sucrose, a disaccharide. The rate of these changes in physical properties and their extent depend on the properties of the fondant and environment, as noted in the previous section .

4.3 Stability and Shelf Life of Fondants and Creams

Fondants can change during storage by losing moisture or, in some rare cases, due to mold growth. Also, over time, the many small crystals can recrystallize, meaning the crystals grow increasingly larger over time, resulting in a coarser fondant. The water activity of fondant is governed by the characteristics of the syrup phase, with water content and total dissolved solids being the important parameters (see Section 3.3).

4.3.1 Moisture Loss

The water activity of a commercial fondant or cream product is likely to be between 0.6 and 0.65, but might be as high as 0.75 for very soft fondants. Since environmental relative humidity is often 50% or lower (except in humid climates), there is usually a net migration of moisture from the candy to the air. Thus, fondants and creams generally tend to dry out and harden over time if exposed to ambient air. Even a coating of chocolate does not completely prevent moisture loss, so that chocolate-coated cream centers also harden over time (albeit at a reduced rate). Packaging the candy in materials with water barrier properties and good seals can reduce the rate of moisture loss and extend shelf life .

4.3.2 Microbial Growth

Osmophilic molds have been known to grow in conditions where water activity is as low as about 0.65. In sugar solutions, reducing water activity to less than 0.65 generally means the dissolved solids in the liquid phase need to be greater than about 75%. Since sucrose at room temperature has a solubility of about 67%, it is clear that a fondant or cream made with only sucrose cannot be stable to mold growth (soluble dissolved solids significantly less than 75%). This means that other sugars, like glucose syrup and invert sugar, are needed to make a stable fondant or cream.

Stability to mold growth and water loss in fondants and creams are governed by water activity, which depends on the type and amount of dissolved sugars in the amount of water remaining in the final product. Fondant with lower final water content is generally more stable since the water activity is usually low enough that it does not support microbial growth . The lower water activity also limits moisture loss to the air during storage by reducing the driving force for moisture loss (the difference in water activity of the fondant to the relative humidity of the air). To enhance stability of fondant to microbial growth, the proper formulation is necessary to ensure that the liquid phase of fondant has sufficient dissolved solids that its water activity is decreased below about 0.65. In general, addition of glucose syrup with low molecular weight sugars, invert sugar or other humectants helps to retard mold growth and prevent moisture loss during storage. The use of invertase to produce glucose and fructose not only softens the cream, but also helps reduce water activity and extend shelf life against microbial issues .

4.3.3 Crystal Coarsening

It has been shown that sugar crystals in fondant grow slowly coarser over time (Lees 1965). According to one study, the percentage of crystals below 16 μm was 98% 1 day after fondant manufacture. This value decreased to 95% after 1 week and to 45% after 1 month of storage. Clearly, the sugar crystals in fondant are quite prone to growing larger over time. However, there may be multiple causes for this coarsening effect. One possibility is that moisture redistribution occurs within the liquid phase of the fondant and this leads to an increase in sucrose crystal size, particularly when moisture loss occurs. However, another mechanism, Ostwald ripening, may also be at work based on the crystalline nature of fondant and no variations in moisture content are necessary for this process to occur.

When crystals of different sizes and shapes are packed closely together, as is the case in fondant and cream, a thermodynamic ripening process can take place. This ripening, or recrystallization, is based on the slight differences in solubility for crystals of different sizes, a phenomenon sometimes called the Gibbs-Thomson effect. It has been well documented that very small crystals, typically less than a few microns in size, are slightly more soluble than large crystals due to a surface curvature effect. Based on this difference in solubility, when two crystals of different sizes are in close proximity, as happens in fondant and cream, the smaller crystal may actually be undersaturated and dissolve, while the larger one is supersaturated and grows. The large crystal appears to grow at the expense of the smaller crystal. This is called Ostwald ripening (Hartel 2001). With millions of crystals packed close together in fondant (some estimates put the average thickness of the liquid phase between crystals as only 0.7–1.0 μm), this scenario repeats itself continuously during storage. The end result is that the mean size of the distribution of crystals increases over time and the fondant becomes coarser to the mouthfeel .

When temperature fluctuates during storage, as when temperature increases during the day and decreases at night, this coarsening is exacerbated (Hartel 2001). In general, when temperature fluctuates, there are subtle changes in fondant as the system seeks to maintain phase equilibrium. That is, when temperature rises, crystals have to dissolve to maintain a saturated solution since solubility increases with an increase in temperature. When temperature goes back down again, the solution is now supersaturated, since it has lower solubility at the lower temperature, and crystals grow. If any small crystals completely dissolve away when temperature is high, they do not renucleate when temperature is lowered and the crystal mass deposits on the remaining crystals. The result is that all crystals get a little larger and the mean size increases with time. This same process is responsible for the coarsening of ice crystals in ice cream, particularly when stored in a frost-free freezer.

Both Ostwald ripening and recrystallization due to temperature fluctuations lead to an increase in mean size over time during storage, a negative consequence in fondants and creams. If crystal coarsening is taken far enough, the fondant or cream may be considered unacceptably coarse. The keys to preventing these effects are (1) to make very small crystals in the first place and (2) then to store the fondant or cream at cool and constant temperature .

5 Potential Problems and Trouble Shooting

As with most confections, there are numerous potential problems that can cause decreased quality in fondants and creams. Controlling all of the myriad factors that go into making a good quality fondant or cream is not always easy. In general, problems related to fondants and creams are due either to problems with improper initial formulation, unsuitable processing conditions or problems that occur during storage.

5.1 Hard Fondant or Cream

One of the potential problems associated with fondants and creams is that they set into a matrix that is too hard for the desired application. This problem may be caused by formulation or processing factors; ascertaining which mechanism (or combination of mechanisms) is the cause of hardening in a specific situation may not be easy. Among the potential causes for hard fondant, one can include (1) water content that is too low for the desired application, (2) sucrose to glucose syrup ratio that is too high, (3) the sugar crystals have become too large and fused together, or (4) insufficient invertase activity during storage in creams.

There are a number of possible causes for low water content, which means the crystal content is higher than desired and the fondant takes on a hard texture. First, cooking temperature might be too high such that too much water is driven off in processing. Upon cooling, excess sugar crystallizes, leading to hard fondant. Alternatively, the creams may have remained in molding starch for too long so that excess water was driven off in the starch. The result would be cream pieces with undesirably low moisture content, high crystal content, and hard texture.

A high sucrose to glucose syrup ratio can lead to hardened fondants and creams through an increase in the crystalline solids content. Glucose syrup reduces the amount of crystalline sucrose at any water content and softens fondant. Addition of humectants also softens fondants and creams .

Even if water content is satisfactory, the sugar crystals must all be small and uniform to give the desired texture. If the sugar crystals become too large or fuse together, the result can be hardened fondant. The main cause of large fused crystals comes from excessive dissolution of fondant in thinning syrup during manufacture of cast creams. Holding the remelted fondant for too long or at high temperatures causes dissolution of sugar crystals (this is often called fondant melting, but is more accurately termed dissolution). When the cream is cooled, it solidifies into a hard matrix as crystals regrow on existing crystals, often causing bridging between adjacent crystals. Alternatively, the bob syrup use to thin the fondant may contain sucrose concentration that is too high. Upon cooling, the excess sucrose in the thinning syrup crystallizes, fusing particles together and causing hard creams.

Invertase is often used to soften hard fondants and creams during storage. If invertase was not added uniformly, if the product is held at temperatures too cool to allow invertase activity, or if the invertase was inactivated from excessive processing temperatures or incorrect pH, softening over time will not occur. If the activity of an invertase solution is suspected, simple comparison tests of hydrolysis of a pure sucrose solution can quickly determine if this is the cause of the problems or not .

5.2 Soft Fondant/Cream

A fondant that is too soft does not hold its shape and is prone to flow or leak through a chocolate shell. Soft fondant is typically due to insufficient crystal content, which can be caused by either high moisture content or inappropriate formulation. High moisture content can be due either to a boiling temperature that is too low or insufficient time in molding starch. If the sucrose content in the initial formulation is too low, there will not be enough crystalline sugar to provide the firmness. Decreasing the amount of glucose syrup or other humectants in the formulation will increase the crystalline content and give a firmer fondant.

Molded creams may be too soft for a number of reasons. For one, the thinning syrup may contain either too much moisture or too little sucrose. Also, excess invertase activity can cause undesirable softening of fondants and creams .

5.3 Sticky Fondant/Cream

Fondant that is too sticky is most likely due to high water content or formulating with too many low molecular weight sugars or inversion during cooking. Stickiness in candy often comes from the presence of simple sugars like fructose and glucose, which are extremely hygroscopic. As they pick up moisture from the air, the candy surface becomes sticky and gradually the entire piece softens excessively as the moisture moves into the candy.

If low molecular weight sugars are present in the initial formulation (i.e., high DE glucose syrup or high fructose corn syrup), the final product will be sticky. Inversion of sucrose during processing can also cause this problem. Excessively long cook times or low pH during cooking can lead to undesirable inversion and problem of sticky fondant and cream. Ensuring a neutral pH of the batch can limit problems with inversion during cooking .

5.4 Coarse Fondant/Cream

The presence of large crystals in fondant or cream leads to the sensory perception of coarse fondant. Controlling crystallization in fondant and cream is critical to obtaining a smooth product. Large crystals can be caused by a number of factors, including (1) improper beating temperature, (2) insufficient beating energy input, (3) crystal formation prior to beating, (4) insufficient crystal modifier in the formulation, or (5) excessive crystal dissolution in bob syrup method of cast cream formation.

As discussed previously, intense beating of fondant at the appropriate beating temperature is necessary to produce the largest number of nuclei and maintain a smooth fondant. Beating temperatures either too high or too low produce fondant with larger crystals, as does less than adequate beating intensity. Furthermore, if crystals are present in the supersaturated sugar solution prior to beating, these crystals have the opportunity to grow to sizes larger than the critical threshold sensory detection size. To maintain a smooth fondant, all of the crystals should be less than about 15 μm, with the average size less than 10 μm.

Improper formulation can also impact crystal size. According to the data in Table 9.5 (Lees 1965), higher levels of glucose syrup led to smaller crystal sizes, especially when optimal beating temperature of 40 °C was used. In this case, the lower total crystalline content found with the higher level of glucose syrup most likely led to smaller crystals. However, other changes, some of which might be considered negative, also result from using higher levels of glucose syrup.

In the casting method of making creams, the characteristics of the thinning syrup and conditions used for thinning fondant are critical to maintaining the small crystal size in the initial fondant. Any time fondant is heated or thinned with bob syrup, some of the initial crystals are dissolved away. Thus, when heated and thinned fondant is cooled again, there are fewer crystals remaining, which must take up all the crystalline phase volume. This means that all crystals grow a little larger. If too many crystals have been dissolved due to excessively warm temperatures or addition of too much thinning syrup, some of the remaining crystals can grow large enough to be detected in the mouth .

5.5 White Surface Discoloration

In certain types of deposited cream candies, a surface discoloration can sometimes form if crystallization is not properly controlled. This problem is most apparent on dark-colored pieces that are not chocolate coated. The problem may arise from uneven heating of the cream prior to depositing. In deposited creams, there is a fine balance between heating sufficiently to reduce viscosity for easy depositing and having sufficiently low temperature to minimize dissolution of the crystals from the fondant. If heating is uneven, a portion of the mass has less crystalline seeds remaining and upon cooling, this region will recrystallize with larger crystals. This results in redistribution of the colors in the region of the larger crystals, leaving white spots or streaks.

Depositing the cream syrup at temperatures above about 82 °C (180 °F) can also lead to discoloration problems, particularly at the flat surface of candy exposed to air (as opposed to the candy in contact with the mold). As the mass cools and sugar crystals grow, there is a release of latent heat from crystallization that focuses on that surface because of the insulating effect of the mold. If depositing temperature is too warm, all seeds in this area may be dissolved by this heat. Without seeds to guide crystallization, the sugar eventually crystallizes randomly as the candy cools, leaving large white spots as the colors are excluded. Careful control of depositing temperature is needed to prevent this problem .

Appendix A.9.1 Calculation of Crystalline and Liquid Phases of Fondant

The crystal content in fondant can be calculated by use of a mass balance, as shown schematically in Figure 9.13, where the concentrated sugar syrup, F, is converted into a fondant with crystal content, C, and liquid phase, P. To find the amount of crystals, the amount of liquid portion, P, of the fondant, and the composition of the liquid phase, the following steps are used:

• First calculate water, sucrose and corn syrup solids in the feed;

• This also gives water and corn syrup solids in the liquid portion of the crystallized fondant (Equations 2 and 3 in Figure 9.13);

• Find sucrose dissolved in liquid portion, P, from solubility Equation 5;

• Sum water, corn syrup solids and sucrose in liquid portion to get total P;

• Subtract P from 100 to get amount of crystals;

• Calculate total dissolved solids from components of P.

Figure 9.13

Mass balance to calculate crystal content and liquid phase concentration in fondant

For example, given a fondant with 12% water content (88% dry solids) and a 70/30 dry basis ratio of sucrose to corn syrup solids, the calculations for 100 g of fondant are:

$$ {\mathrm{W}}_{\mathrm{F}}={\mathrm{W}}_{\mathrm{p}}=(0.12)(100)=12\mathrm{g}{\mathrm{H}}_2\mathrm{O} $$

Sucrose is 70% dry solids, which is 88% of total:

$$ {\mathrm{S}}_{\mathrm{F}}=(0.7)(88)=61.6\mathrm{g} sucrose $$

CS is 30% of dry solids, which is 88% of total (note that the sum of W_F + S_F + CS_F = 100, which it should since we started with 100 g fondant :

$$ {\mathrm{CS}}_{\mathrm{F}}={\mathrm{CS}}_{\mathrm{P}}=(0.3)(88)=26.4\mathrm{g} \mathrm{CS} $$

The next step is to determine the amount of sucrose in the liquid portion (P). For that, the concentration of corn syrup solids on a 100 g H₂O basis (for Equation 5) must be known. In P, there is 26.4 g CS and 12 g H₂O, so :

$$ {\displaystyle \begin{array}{l}{\mathrm{CS}}_{\mathrm{P}}=26.4\mathrm{g} \mathrm{CS}\div 12\mathrm{g} {\mathrm{H}}_2\mathrm{O}\hfill \\ {}=2.2\left[\mathrm{gCS}/{\mathrm{gH}}_2\mathrm{O}\right]=220\left[\mathrm{gCS}/100\mathrm{g} {\mathrm{H}}_2\mathrm{O}\right]\hfill \end{array}} $$

Then, from Equation 5:

$$ {\displaystyle \begin{array}{l}\begin{array}{l}{\mathrm{S}}_{\mathrm{P}}=210.38-(.3424){\mathrm{CS}}_{\mathrm{P}}\hfill \\ {}=210.38-(0.3424)(220)\hfill \\ {}=135.05\left[\mathrm{g} sucrose/100\mathrm{g} {\mathrm{H}}_2\mathrm{O}\right]\hfill \end{array}\hfill \\ {}{\mathrm{S}}_{\mathrm{P}}=1.35\left[\mathrm{g} sucrose/\mathrm{g} {\mathrm{H}}_2\mathrm{O}\right]\hfill \end{array}} $$

But, there are 12 g H₂O in P, so S_P is:

$$ {\displaystyle \begin{array}{l}{\mathrm{S}}_{\mathrm{P}}=1.35\left[\mathrm{g} sucrose/\mathrm{g} {\mathrm{H}}_2\mathrm{O}\right]\left(12\mathrm{g} {\mathrm{H}}_2\mathrm{O}\right]\hfill \\ {}=16.21\mathrm{g} sucrose\hfill \end{array}} $$

Now, all components of P are known and they can be summed to get the total of the solution phase of the fondant:

$$ {\displaystyle \begin{array}{l}{\mathrm{S}}_{\mathrm{P}}+{\mathrm{CS}}_{\mathrm{P}}+{\mathrm{W}}_{\mathrm{P}}=16.21+26.4+12\hfill \\ {}=54.61\mathrm{g}\, total\ \ \mathbf{Liquid} \; \mathbf{Phase},\mathbf{P}\hfill \end{array}} $$

From Equation 1, C is found as :

$$ {\displaystyle \begin{array}{l}\mathrm{C}=100-54.61\hfill \\ {}=45.39\mathrm{g} of\ \ crystals\ \mathbf{Solid} \mathbf{Phase},\mathbf{C}\hfill \end{array}} $$

Furthermore, the dissolved solids content of the liquid portion, P, can be found as

$$ {\displaystyle \begin{array}{l}\left({\mathrm{S}}_{\mathrm{P}}+{\mathrm{CS}}_{\mathrm{P}}\right)/\mathrm{P}=\left(16.21+26.4\right)/54.61\hfill \\ {}=0.78 or\ \ 78\%\hfill \\ {}\mathbf{Dissolved}\ \ \mathbf{solids}\ \ \mathbf{in}\ \ \mathbf{P}\hfill \end{array}} $$

To summarize, a fondant made with 12% water content and a 70/30 sucrose to corn syrup ratio (dry solids basis), has 45.39% crystals and a liquid portion of 54.61%, as a saturated sugar solution with a total dissolved solids concentration of 78%.