Nanomaterials in Food Industry and Packaging

Abstract

Nanomaterials are playing significant role in agriculture, by inclusion into fertilizer compounds and supplyin.g the necessary nutrition for the growing plants. Nanomaterials with the nanotechnology used in fertilizers and plant protecting are divided into three categories such as (1) nanoscale fertilizer input, (2) nanoscale additives, and (3) nanoscale coatings or host materials for fertilizers.

Without food we cannot survive, and that is why issues affecting food industry are so important.

Marcus Samuelsson

2.1 Nanomaterials in the Agriculture

Nanomaterials are playing significant role in agriculture, by inclusion into fertilizer compounds and supplying the necessary nutrition for the growing plants. Nanomaterials with the nanotechnology used in fertilizers and plant protecting are divided into three categories such as (1) nanoscale fertilizer input, (2) nanoscale additives, and (3) nanoscale coatings or host materials for fertilizers (Rai et al. 2015). Nanobiotechnology is the branch of nanotechnology dealing with nanobiology, nanoobjects, and nanodevices for various technological processes (www.nature.com), while the bio-nanotechnology is a fusion of biology and nanotechnology based on the principles and chemical pathways of living organisms, referring to the functional applications of biomolecules in nanotechnology (Bagchi et al. 2013). Nanotechnology allows broad advances in agricultural research, such as reproductive science and technology, conversion of agricultural and food wastes to energy, and other useful by-products through enzymatic nanobioprocessing, disease prevention, and treatment of plants using various nanoscale devices with novel properties. “Smart Delivery Systems” in agriculture should possess combinations of time controlled, specifically targeted, highly controlled, remotely regulated/preprogrammed/self-regulated and multifunctional characteristics to avoid biological barriers for successful targeting (Nair et al. 2010). Applications of metal nanoparticles with size-dependent properties such as magnetism (magnetic NPs), fluorescence (QDs), or photocatalytic degradation (metal oxide NPs) exhibiting biotechnological applications in sensor development, agrochemical degradation, and soil remediation are represented in Table 2.1.

Table 2.1 Applications of nanotechnology in agriculture (Ghormade et al. 2011)

Nanomaterials and biocomposites are possessing properties such as stiffness, permeability, crystallinity, thermal stability, solubility, and biodegradability necessary for formulating and production of nanopesticides, which can increase dispersion and wettability of agricultural formulations and reduction in organic solvent runoff. Table 2.2 represents some of the recent applications of nanomaterials in agricultural plant protection and production (Khot et al. 2012).

Table 2.2 Nanomaterials in agricultural plant protection and production (Khot et al. 2012)

Recent spraying of pesticides involves either knapsacks (or pack bag) that deliver large droplets (9–266 μm) associated with splash loss or ultralight volume sprayers for controlled droplet application with smaller droplets (3–28 μm) causing spray drift, where constraints due to droplet size may be overcome by using encapsulated NP or nanosized pesticides, represented in the Fig. 2.1 (Ghormade et al. 2011).

Fig. 2.1

Schematic representation of incorporation of nanoformulations in spray droplets to maximize efficient spraying. a Spray droplets; b droplets containing nanoparticles loaded with pesticide; c droplets containing nanosized pesticides (Ghormade et al. 2011, reproduced with permission of Elsevier)

2.2 Nanomaterials in the Food Science

Food science—is the study of the chemical and physical properties of food and of changes that may occur during processing, storage, etc. (Oxford Dictionary 2016). Nanotechnology has the potential to impact many aspects of food and agricultural systems, such as “food security, disease treatment delivery methods, new tools for molecular and cellular biology, new materials for pathogen detection, and protection of the environment. Examples of nanotechnology as a tool in the food industry are (1) increased security of manufacturing, processing, and shipping of food products through sensors for pathogen and contaminant detection, (2) devices to maintain historical environmental records of a particular product and tracking of individual shipments, (3) systems that provide integration of sensing, localization, reporting, and remote control of food products (smart/intelligent systems) and that can increase efficacy and security of food processing and transportation, and (4) encapsulation and delivery systems that carry, protect, and deliver functional food ingredients to their specific site of action. Nanodispersions and nanocapsules are the functional ingredients of drugs, vitamins, antimicrobials, antioxidants, flavorings, colorants, and preservatives. Association colloids are surfactant micelles, vesicles, bilayers, reverse micelles, and liquid crystals which have been used for many years to encapsulate and deliver polar, nonpolar, and/or amphiphilic functional ingredients. Nanoemulsions are produced during microfluidizing process by high-pressure valve homogenizers, with droplet diameters of less than 100–500 nm. Nanostructured multilayer emulsions consist of oil droplets (the core) surrounded by nanometer thick layers (the shell) comprised of different polyelectrolytes. These layers are formed using a layer-by-layer (LbL) electrostatic deposition method involving sequential adsorption of polyelectrolytes onto the surfaces of oppositely charged colloidal particles” (Weiss et al. 2006). Figure 2.2 is representing LbL approach for encapsulation of oil droplets in an oil–water (O/W) emulsion.

Fig. 2.2

Schematic for formation of a number of nanolayers around particles (Weiss et al. 2006, reproduced with permission of John Wiley and Sons)

The composition, thickness, structure, and properties of the multilayered nanolaminate represented in the Fig. 2.3 formed around the edible object could be controlled in a number of ways: (1) changing the type of adsorbing substances in the dipping solutions, (2) changing the total number of dipping steps used, (3) changing the order that the object is introduced into the various dipping solutions, and (4) changing the solution and environmental conditions (pH, ionic strength, dielectric constant, temperature).

Fig. 2.3

Schematic representation of coating an object with multilayers using a successive dipping and washing procedure (Weiss et al. 2006, adapted with permission of John Wiley and Sons)

Nanotechnology is directed for food applications by two different approaches as “bottom up” and “top down.” The top-down approach in the food industry is based on a physical processing of the food materials, such as grinding and milling. For example, dry milling technology can be used to obtain wheat flour of fine size that has a high water-binding capacity and to improve antioxidant activity in green tea powder (Ravichandran 2010). The bottom-up approach in the food industry deals with building and growing of larger structures from atoms and molecules, for example, organization of casein micelles or starch and protein folding (Rai et al. 2015).

2.2.1 Nanomaterials in the Food Processing

Food processing is defined as action of performing a series of mechanical or chemical operations on food in order to change or preserve it (Oxford Dictionary 2016). Food processing utilizes nanoparticles for improvement of foods nutritional quality, flow properties, flavor, color, and stability or to increase shelf life (Berekaa 2015). “Nanotechnology in Food and Food Processing Industry Worldwide,” earlier predicted that nanofood market will surge from $10 billion to $30.4 billion in 2015, because hundreds of companies are conducting research and development (R&D) on the use of nanotechnology to engineer, process, package, deliver food and nutrients to our shopping baskets and plates” (Ravichandran 2010).

2.2.2 Nanoencapsulation

Nanoencapsulation in food processing is defined as technology to pack substances in miniature at the nanoscale also improve food rehydration; Edible coatings are used on fruits, vegetables, meats, chocolate, candies, and bakery products, by serving as moisture, lipid, and gas barriers (Couch et al. 2016). Nanoencapsulation is applied for manufacturing of confectionary products, pharmacological and dietary supplements, and nanocarrier food systems (Ezhilarasi et al. 2012). Nanoencapsulation can be achieved by using of three methodologies: (1) physical, which is based on the spray drying–coating, extrusion, and spray drying, (2) physiochemical processes based on the simple or complex coacervation and entrapment into liposomes, and (3) chemical processes: interfacial polymerization and molecular inclusion (Quintanilla-Carvajal et al. 2010). Use, advantages, and examples of compositions produced by nanoencapsulation are listed in the Table 2.4. Nanoencapsulation techniques are classified and summarized in the Scheme 2.1.

Scheme 2.1

Classification of nanoencapsulation techniques (adapted from Quintanilla-Carvajal et al. 2010)

Three types of nanosystems reported as wall materials used in nanoencapsulation of food ingredients such as (1) lipid-based nanosystems including nanoliposomes, nanocochleates, colloidosomes, solid lipid NPs, and archeosomes, (2) polymeric-type nanosystems including nanofibers, carbohydrate-based NPs, starch, cellulose, pectin, guar gum, alginate, chitosan, and dextran, and (3) protein-based nanosystems include corn protein or zein ultrafine fibers and milk protein nanotubes (Paredes et al. 2016; Yada 2012).

2.2.3 Nanoemulsification

Nanoemulsification in food processing is preparation of nanoemulsions by using of techniques such as “phase inversion composition, high-pressure homogenization, ultrasonication and microfluidization” (Quintanilla-Carvajal et al. 2010). Nanoscale delivery systems such as microemulsions, emulsions, nanoemulsions, multiple emulsions, multilayer emulsions, solid lipid nanoparticles, liposomes, biopolymer nanoparticles, and microgels need to be selected for particular application in food industry based on the following criteria: (1) safety, (2) commercial viability, (3) food-matrix compatibility, (4) robustness, (5) performance, and (6) labeling requirements (McClements 2015a). Use, advantages, and examples of compositions produced by nanoemulsification are represented in the Table 2.3. Hydrocolloid proteins derived from milk, egg, soy, collagen, and gelatin are most commonly used as emulsifiers in food emulsions (Santana et al. 2013).

Table 2.3 List of selected nanotechniques used by different food industries for food processing (Pradhan et al. 2015)

Formation of water–oil (w/o) and oil–water (o/w) microemulsions is associated with the negative, null, and positive curvatures represented in the Fig. 2.4. Curvature is defined as difference between the areas occupied by droplets hydrophilic head and lipophilic tail (Thiam et al. 2013). Negative curvature is characterized by the contact angle of θ < 90° for hydrophobic particles, while the contact angle in positive curvature is θ > 90° for hydrophilic particles in stabilized emulsions (Kralchevsky et al. 2005).

Fig. 2.4

Monolayer curvature of w/o, bicontinuous, and o/w microemulsions (Santana et al. 2013)

2.2.4 Theory of Nanoemulsions Formation

The necessary items for preparation of nanoemulsions are oil, water, emulsifier, and energy input (mechanical or physicochemical). The free energy ${(\Delta }G\text{)}$ required for nanoemulsion formation is expressed by the following equation (Komaiko and McClements 2016):

$$\Delta G =\Delta A\gamma - T\Delta S$$

(2.1)

where, $\Delta A\gamma$ is the free energy necessary for increase the oil–water interface (where A is the interfacial area and γ is the interfacial tension) and $T {\Delta} S$ is the free energy associated with increasing the number of possible arrangements of droplets in a nanoemulsion, where T is the temperature and S is the entropy (Scheme 2.2).

Scheme 2.2

Classification of nanoemulsification techniques (adapted from Han et al. 2012; Sugumar et al. 2013; Santana et al. 2013)

For emulsification by stirring the input of mechanical energy is provided by stirrer, where stirrer generate macro-eddies (whirlpool) which is later turns into turbulent micro-eddies with the length characteristic $- \eta$, called as Kolmogorov length scale of turbulence (Bakker 2000):

$$\eta = \left( {\frac{{\nu^{3} }}{\varepsilon }} \right)^{1/4}$$

(2.2)

where, $\eta$ is kinematic viscosity of the solution (ν) and the dissipation rate (ε) which is the power input by the stirrer (P) per mass (m).

The minimum size (radius) of stable droplets in nanoemulsions can be theoretically produced during homogenization is estimated by the following equation (McClements 2015b):

$$r_{ \hbox{min} } = \frac{{3 \cdot\Gamma _{\text{sat}} \cdot\upphi}}{{c_{s} }} = \frac{{3 \cdot\Gamma _{\text{sat}} \cdot\upphi}}{{c_{s}^{{\prime }} (1 -\upphi)}}$$

(2.3)

where, $\Gamma _{\text{sat}}$ is the excess surface concentration (or surface load) of the emulsifier at saturation (kg m⁻²); $\upphi$ is the disperse phase volume fraction; $c_{s}$ is the concentration of emulsifier in the emulsion (kg m⁻³); c’ _s is the concentration of emulsifier in the continuous phase (kg m⁻³).

High interfacial tension existing between the outer phase and the inner phase of a nanosized droplet requires more energy for nanoemulsions formation, and the small volume fraction of dispersed phase causes spherical droplets formation, whereas the pressure inside of droplets with curved interface and the Laplace pressure ${(\Delta }p)$ for non-spherical droplets can be expressed by Grumezescu (2016):

$$p = 2\gamma \,\text{/}\,r$$

(2.4)

and the

$$\Delta p = \gamma \left( {\frac{1}{{r_{1} }} + \frac{1}{{r_{2} }}} \right)$$

(2.5)

respectively, where $\gamma$ is an interfacial tension, $r_{1}$ and $r_{2}$ are the radii of curvature of the droplets.

The Laplace pressure for absolutely spherical nanoemulsion droplets where $r_{1} = r_{2} = r$ can be expressed by Tadros (2013):

$$\Delta p = \frac{2\gamma }{r}$$

(2.6)

The hydrophil/lipophil balance (HLB) number is used for classification of surfactants (Santana et al. 2013). For case of the surfactant-mediated emulsification, hydrophil/lipophil balance (HLB) number is obtained between 0 and 20, where numbers >10 define hydrophilic surfactants and the number <10 attributed to lipophilic surfactants, which can be determined by the following equation (Eastoe and Tabor 2014):

$${\text{HLB}} = \frac{{20M_{h} }}{M}$$

(2.7)

where, $M_{h}$ is the mass of hydrophilic portion of the molecule, M is the total molecular mass.

Hydrophilic/lipophilic deviation (HLD) number for ionic surfactant used for nanoemulsification can be expressed by the Eq. (2.8) below (Salager et al. 2013):

$${\text{HLD}} = \left[ {\alpha^{\prime} - k^{\prime} \times {\text{EACN}}} \right] + \left[ {a^{\prime} \times C_{A} + b^{\prime} \times { \ln }\,(C_{s} ) + c^{\prime} \times (T - T_{0} )} \right]$$

(2.8)

here, α and k are the constants depending on the surfactant type; EACN is the equivalent alkane carbon number of the oil phase, C _A is the concentration of any alcohol present in the system (wt%), a is a constant that depends on the type of alcohol present, C _S is concentration of any salt present in the system (wt%), b is a constant depending on the type of salt present, T is the temperature, T ₀ is a reference temperature (°C), and c is a constant that depends on how the properties of a particular surfactant change with temperature.

Single microdroplets freely moved in the solution are referred to micelles (Friberg 1990), which are also can be defined as colloidal ions composed of an oriented arrangement of molecules, or an aggregate of polymerized molecules joined together (Collins Dict. 2016). The difference between micelle and microemulsion aggregates is that micelles are made of surfactant dispersed only in water, while microemulsion can contain an oil phase and larger in size than micelles (Langevin 1992). Critical micellar concentration (CMC) is concentration factor for micelle formation, which is linearly proportional to the surfactant concentration and can be determined from the Gibbs equation (Páhi et al. 2008):

$$\Delta G_{\text{mic}} = RT \times { \ln }\,{\text{CMC}}, \;\alpha = 1$$

(2.9)

where, $\Delta G_{\text{mic}}$ is the Gibbs energy for micelle formation, ${ \ln }\,{\text{CMC}}$ is the critical micelle concentration, $\alpha$ is degree of dissociation for Stern particles formed by ionic micelles, R gas constant (8.31 J mol⁻¹ K⁻¹), and T is the temperature.

Nanoemulsions exhibit rheological properties, which are characterized by droplets deformation and flow due to stress, pressure, and strain (Wilking 2008). The Brookfield rotational R/S Plus rheometer with a cone-plate measuring system was used for rheological analyses (Jaworska et al. 2015). Kinetically stable nanoemulsions may undergo breakdown by: (1) gravitational separation which results in sedimentation and creaming; (2) flocculation; (3) coalescence or the Ostwald ripening; leading to (4) phase separation (McClements 2015b).

2.3 Nanomaterials in the Food Packaging

Not so far several methods for food preservation have been used such as salting, curing, canning, refrigerating, freezing, use of preservatives, irradiation, and the hydrostatic pressure (Pitt and Hocking 2009). The term of active packaging was introduced in 1987 by Labuza for improvement of shelf life and nutritional quality of fresh and extended shelf-life food (Labuza and Breene 1989). Also, food packaging techniques should be designed for keeping the food flavor, quality, and protect from infestation of microorganisms which leads to food spoilage (Pradhan et al. 2015). Packaging types such as active, intelligent, and smart were reported recently (Fig. 2.5).

Fig. 2.5

a Photograph of various polyethylene wrapping and packages; b Illustration of the active packaging which extends shelf life of food product by protecting food from spoilage. Chemical reaction will occur inside the package between citric acid released from fruits and the sodium bicarbonate included into absorbent pad

2.3.1 Active Packaging

The active packaging provides the inert barrier between the food product and outside environment and reacts with the food product for extension of the shelf life and good conditions (Grumezescu 2017). Components of the active packaging for food include (1) nanocomposites (metal ions of silver, copper, gold and metal oxides of TiO₂, MgO), (2) antimicrobial films (antibacterial/antifungal compounds like sodium benzoate and benomyl, acid, silicate, ethanol, zinc, elements (Si, Na, Al, S, Cl, Ca, Mg, Fe, Pd, and Ti), edible clove, pepper, cinnamon, coffee, chitosan, antimicrobial lysozyme, and bacteriophages), (3) gas scavengers [TiO₂, iron powder, silicates, sulfites, chlorides, polymeric scavengers, elements (Fe, Si, Ca, Al, Na, Cl, K, Mg, S, Mn, Ti, Co, V, Cr, and P)] (Ahvenainen 2003; Brockgreitens and Abbas 2016). Enzymatic oxygen scavenging is achieved by the chemical reaction between alcohols generated in the food product and the alcohol oxidase enzyme (Lee et al. 2015):

$${\text{R}} - {\text{CH}}_{2} {\text{OH}} + {\text{O}}_{2} \mathop{\longrightarrow}\limits^{Alcohol\;oxidase}{\text{R}} - {\text{CHO}} + {\text{H}}_{2} {\text{O}}_{2}$$

Materials and construction of the Tetra Pak™ packaging which have been applied for storage and shelf-life extension of milk products in Switzerland since 1951 are consist of carton board, polyethylene, aluminum sheet, and repeatable polyethylene, carton layers (Kadoya 1999). Examples of various packages utilizing plastic and Tetra Pak for food products shelf-life extension are shown in the Fig. 2.6.

Fig. 2.6

Photograph of various food packaging items applied for storage of fish, sea food, beverage, and pastry products

Polymers used in the food packaging in the form of plastic trays, lids, pouches, bottles, and containers made from polyolefin, copolymers of ethylene, substituted olefins, polyesters, polycarbonate, and polyamide (nylon) are shown in the Table 2.4.

Table 2.4 Polymers used in the Food Packaging (adapted from Bhunia et al. 2013)

Nanoclay–polymer composites were used for improving of gas barrier properties of food packages. The most often used one is montmorillonite (also called as bentonite), with natural nanoscalar layered structure that can restrict the permeation of gases when incorporated into a polymer. Barrier improvement mechanism of nanoplate-based composites is based on the well-known “tortuous path” principle depicted in the Fig. 2.7 (Wyser et al. 2016).

Fig. 2.7

Addition of nanoplates increases tortuosity and decreases permeability (Wyser et al. 2016, reproduced with permission of John Wiley and Sons)

2.3.2 Intelligent and Responsive Packaging

Intelligent packaging is capable of carrying out detecting, sensing, recording, tracing, communicating, and applying scientific logic to extend shelf life, enhance safety, improve quality, provide information, and warn about possible problems (Yam 2009). The components of the intelligent packages are (1) indicators (methylene blue, acid, antioxidants, mineral oil and sugar, elements (Na, K, Ca, Si, Al, and Mg) (Ahvenainen 2003). Responsive packaging technologies are based on the integration of a sensor or sensing interface on the packaging film in real-time and continuous quality monitoring by implementing of 3 important design features: prevention of cross-contamination, selection of the target analytes, and choice of the transduction system. The components of responsive packages are stimuli-responsive materials, hydrogels, surfaces, particles, and supramolecules (Brockgreitens and Abbas 2016). Oxygen scavengers used in the intelligent packaging prevent microbial growth, off flavors and off odors development, color changes and nutritional losses, and reduction in the shelf life of foods based on the following mechanism of iron oxidation (Kerry et al. 2006):

$$\begin{aligned} & {\text{Fe}} \to {\text{Fe}}^{2 + } + 2{\text{e}}^{ - } \\ & \frac{1}{2}{\text{O}}_{2} + {\text{H}}_{2} {\text{O}} + 2{\text{e}}^{ - } \to 2{\text{OH}}^{ - } \\ & {\text{Fe}}^{2 + } + 2{\text{OH}}^{ - } \to {\text{Fe}}({\text{OH}})_{2} \\ & {\text{Fe}}({\text{OH}})_{2} + \frac{1}{4}{\text{O}}_{2} + \frac{1}{2}{\text{H}}_{2} {\text{O}} \to {\text{Fe}}({\text{OH}})_{3} \\ \end{aligned}$$

2.3.3 Smart Packaging

Smart packaging can be defined as small and inexpensive labels or tags attached onto primary packaging such as pouches, trays, and bottles, or more often onto secondary packaging such as shipping containers to facilitate communication throughout the supply chain (Yam et al. 2005). Carbon dioxide absorbers and generators can be used in sachet or label form to reduce the respiration rate, and eliminate or minimize the oxygen concentration, which can cause quality deterioration of fruits and vegetables (Lee et al. 2015):

$${\text{Ca}}({\text{OH}})_{2} + {\text{CO}}_{2} \to {\text{CaCO}}_{3} + {\text{H}}_{2} {\text{O}}$$

Modified atmospheric packaging (MAP) is applied to extend the shelf life by removing or replacing the air surrounding food products, altering the amounts of carbon dioxide (CO₂) and nitrogen (N₂), eliminating extension of the post-harvest life, thus prolong the primary fresh conditions of food products (vegetables, fruits, meat, and fish) (Lee et al. 2015).

However, use of some components in the food packages and preservatives manufacture such as silver, surfactant, lipid, protein, carbohydrate nanoparticles, and carbon nanotubes in emulsified form caused health impairments (Table 2.5).

Table 2.5 Effect of nanoemulsion in human system (Pradhan et al. 2015)

Case Study 2.1 Use of clay nanoparticles to improve plastic packaging for food products

“Clay nanoparticles dispersed throughout the plastic package are able to block oxygen, carbon dioxide, and moisture from reaching the fresh meats or other foods, also makes the plastic lighter, stronger, and more heat-resistant” (Ravichandran 2010). “Nanoclays have been added to a range of polymers and used for processed meats, cheese, confectionery, cereals, and boil-in-the-bag foods applications, as well as in extrusion-coated packaging materials for fruit juices, dairy products, and co-injection processes for the manufacture of beer and soft drink bottles” (Wyser et al. 2016). “Clays and layered silicates such as montmorillonite, hectorite, saponite, fluoromica, fluorohectorite, vermiculite, kaolinite, and magadiite are able to reinforce by polymers and form nanocomposite structures” (Alexandre and Dubois 2000) which are useful for food packaging applications represented in the Fig. 2.8. Such nanocomposites form by “penetration of polymers chains into the interlayer region of the clay, producing ordered multilayer structure with alternating polymer/inorganic layers at a repeated distance of a few nanometers” (Azeredo 2009).

Fig. 2.8

Scheme of different types of composite arising from the interaction of layered silicates and polymers: a phase-separated microcomposite; b intercalated nanocomposite, and c exfoliated nanocomposite (Alexandre and Dubois 2000)

Appendices

Questions and Exercises

• 1. Describe the role of nanomaterials in agriculture and define the term nanobiotechnology.

• 2. What kind of nanoparticles are included into pesticides used for agricultural purpose?

• 3. Explain the controlled spray droplet system application of nanoformulations in pesticides.

• 4. Give definitions for the terms: food science, association colloids, and nanoemulsions.

• 5. What are the components and functional ingredients of drugs, vitamins, antimicrobials, antioxidants, flavorings, colorants, and preservatives?

• 6. Define the term nanolaminate applied for food industry and describe top-bottom and bottom-up approaches in the food science.

• 7. Define the term food processing, nanoencapsulation, and nanoemulsification.

• 8. Classify the main techniques used for nanoencapsulation of substances in the food industry.

• 9. Classify the main techniques used for nanoemulsification in the food industry.

• 10. What kinds of nanocomposites can be used for nanoencapsulation and nanoemulsification in the food industry?

• 11. Describe the principle of emulsification based on the input energy, interfacial tension, and oil–water interface.

• 12. Describe the relation between nanoemulsion droplet size and emulsion concentration during homogenization process.

• 13. Describe the functions of the Laplace pressure for spherical and non-spherical droplets.

• 14. What is importance of the hydrophil/lipophil balance (HLB) and the hydrophilic/lipophilic deviation (HLD) numbers during emulsification?

• 15. What kind of factors can cause nanoemulsions rheology and breakdown processes?

• 16. Describe the principles of active, intelligent, and smart packaging in shelf-life and quality extension of food products.

• 17. What kind of human health impairments can appear due to hazardous components used in the food packages?

Problem drills

• 1. Calculate the surface tension for spherical hydrocarbon droplet with the radius of 100 nm if the Laplace pressure $\Delta p = 10^{6} \;{\text{Pa}}$ (10 atm.).

• 2. Diameters of the oil emulsion droplets obtained by hand shaking and shaking by mixer are 15 and 2.8 μm, respectively. Calculate the dispersity, specific surface area of droplets obtained by mixer, and hand shaking and the dispersity ratio, if the density of oil droplets is $1.5 \times 10^{3} \;{{\text{kg}} \mathord{\left/ {\vphantom {{\text{kg}} {{\text{m}}^{ 3} }}} \right. \kern-0pt} {{\text{m}}^{ 3} }}$.

• 3. Draw the structure for silver iodide (AgJ) micelle formed by the chemical reaction: ${\text{AgNO}}_{3} + {\text{HI}} \to {\text{AgI}} + {\text{HNO}}_{3}$, if AgNO₃ used as stabilizing agent. Show charges for ions in the colloidal micelle particle.

• 4. Find the Gibbs energy ${(\Delta }G_{mic} )$ for micelle formation at the critical micelle concentration of 0.50 and the temperature of 25 °C.

• 5. Find the mass of hydrophilic molecule portion for Brij^® S10 surfactant with molecular formula of C₁₈H₃₇(OCH₂CH₂)_nOH, where n ~ 10 and the HLB number of 12 used in emulsification.

Answers:

• 1. $\gamma = 50\,{\text{mN}}\,{\text{m}}^{ - 1}$

• 2. $D_{\text{mixer}} = 3.57 \times 10^{5} \,{\text{m}}^{ - 1}$; $D_{{{\text{hand}}\,{\text{shaking}}}} = 6.66 \times 10^{4} \,{\text{m}}^{ - 1}$; $S_{\text{specific}}^{\text{mixer}} = 1.42 \times 10^{2} \,{\text{m}}^{2}$; $S_{\text{specific}}^{{{\text{hand }}\,{\text{shaking}}}} = 2.66 \times 10^{2} \,{\text{m}}^{2}$; ${{D_{\text{mixer}} } \mathord{\left/ {\vphantom {{D_{\text{mixer}} } {D_{{{\text{hand}}\;{\text{shaking}}}} }}} \right. \kern-0pt} {D_{{{\text{hand}}\;{\text{shaking}}}} }} = 5.3$ and ${{S_{\text{specific}}^{\text{mixer}} } \mathord{\left/ {\vphantom {{S_{\text{specific}}^{\text{mixer}} } {S_{\text{specific}}^{{{\text{hand}}\;{\text{shaking}}}} }}} \right. \kern-0pt} {S_{\text{specific}}^{{{\text{hand}}\;{\text{shaking}}}} }} = 0.5$.

• 3. Structure of the silver iodide micelle:

  

• 4. −7.42 kJ/mol.

• 5. 426.