1 Introduction

According to the United Nations Environment Programme (UNEP), plastic contributes to more than a third of the production in the packaging sector, such as bottles, containers, and grocery bags [1]. By 2050, around 12,000 million metric tons of plastic waste will be accumulated, leading to an increase in global warming and carbon footprint on the earth if the current consumption does not decrease [2, 3]. Paper-based packaging is the new sustainable alternative in the packaging sector because of its biodegradability. Some commercial-based applications are baking paper, popcorn bags, milk cartons, and food containers such as beverage cups [4].

Paper and paper-based cardboard contribute around 31% of the global packaging segment, primarily used in the food packaging sector, which provides containment, protection, and communication between consumers and the product [5]. Paper and paper-based materials are widely used in food packaging as the paper is lightweight and has good printability and recyclability [6]. Paper as a food packaging material has some limitations, including low barrier mechanical, and functional properties. The low barrier to oxygen and water resistance of paper leads to oxidation, moisture loss, and other issues for food products [7]. Due to its lower physical and mechanical strength, paper-based packaging materials can tear, get damaged, and deteriorate, affecting the shelf life of the product [8]. However, paper-based active antioxidant and antimicrobial properties can protect food products from losing flavor, aroma, and sensory properties [3]. Research has been conducted to address the challenges in paper food packaging using advanced materials and technologies. Coating of paper has emerged as a promising approach to overcome these limitations. Recently, metals, synthetic polymers, dyes, and lipids have been used as coating materials to enhance the properties of paper, employing traditional methods such as solution casting, solvent casting, and dip coating [9, 10]. Utilizing conventional paper-coating materials and technologies impacts food product quality, human health, cost, and the environment [11]. Therefore, as demand for safe food increases, the synthetic coating material in the paper coating is reduced with a biodegradable and safe coating material [12]. Natural coating material such as starch, cellulose, protein, polysaccharides, and lipids are used for coating paper, which is low cost and can improve paper properties [13, 14]. Several methods are used for the paper coating, such as solution casting and dipping, spray coating, electrospinning, and extrusion.

Biopolymer coating for food packaging applications has gained interest due to the increasing environmental concerns caused by petrochemicals. Chitosan, starch, proteins, lipids, and other biopolymers have improved paper barrier properties, i.e., water vapor barrier, mechanical properties, gas barrier, and oxygen permeability rate when employed in paper coating [15]. The active property of paper is low, and it can be improved by coating bioactive substances on paper. As per research conducted by Wang et al. [16], paper is coated with chitosan and montmorillonite solution using the rod coating method, and the mechanical and barrier properties of the coated paper were improved than the control paper.

Paper can be used for active, smart, and intelligent food packaging applications with the help of coating techniques [17]. Coating bioactive compounds on paper significantly enhanced the paper’s antioxidant and antimicrobial properties [18]. Paper-based indicators and sensors for smart food packaging applications can be made with a paper-coating list of prepared sensors presented in Table 1. As per the study conducted by Tirtashi et al. [19], the filter was coated with deacetylated chitosan, tetraethylorthosilicate zinc oxide, and anthocyanin solution using the dip coating method; the coated paper used as a pH-responsive indicator in smart packaging of milk. Paper coating has been one of the most significant methods in the food packaging sector, and it is used to improve functional properties. Table 1 and Fig. 1 show the published articles on paper coating for food packaging applications. This review aims to briefly describe the approach for the fabrication of coating and strategies to improve barrier, mechanical, and functional properties of paper for further application in food packaging.

Table 1 Active paper-coating methods and their effects on the properties of food packaging paper
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Fig. 1
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Number of published articles related to coating paper for food packaging applications (searched on the Web of Science with the following keyword: “coated paper-based food packaging or paper coating food packaging applications”) from 2012 to 2023

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2 Coating methods

The physical properties of paper are affected by the many coating techniques, such as dip coating, solvent casting, and bar coating techniques. The functional properties of the coated paper can be extended or improved by novel coating techniques like electrospinning, 3D printing, spray coating, and multilayer coating techniques. Paper coating methods and their food packaging applications are summarized in Table 2 and briefly discussed below:

Table 2 Paper-coating methods and coated paper–based food packaging applications
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2.1 Dip coating

Dip coating is a traditional paper coating method in which paper is dipped into a coating solution, taken out after some time, and dried at a suitable time and temperature. Dip coating is a four-step process: immersion, dwelling, withdrawal, and paper drying, as depicted in Fig. 2. The processes involved in coating affect the quality of paper, as dipping time will affect the thickness, shear strength, and barrier properties of paper sheets [20]. In contrast, the viscosity of the solution affects the uniformity. The dipping time depends on the paper, solution viscosity, and temperature. The substrate should be fully immersed in the solution, and a thin layer should be deposited on the paper. The solution temperature should be maintained for proper paper dipping. The paper should be removed at optimum speed, lowering the withdrawal form strip over the paper. Strip formation affects the homogeneity of the coating. Drying is a critical phase that may be affected by various external factors, airflow, and a consistent evaporation rate. Dip coating is an easy and widely used process because of its low cost and includes uniform coating covering on paper sheets [21].

Fig. 2
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Schematic representation of the paper coating using the dip coating method

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Dip-coated paper can potentially improve food packaging and shelf life. The mechanical characteristics of dip-coated paper, such as its tensile strength and the energy it absorbs per unit area, are better than those of uncoated paper [21]. Research by Nassar and Youssef [22] utilized rice straw silver nanoparticles and coated on paper to improve paper properties using the dip coating method. The dip coating method is extensively used for paper-based food packaging applications. Some drawbacks of the dip coating method are that curved substrate is challenging to coat uniformly, solution wastage during the coating process and time required for drying will be more, so this process is time-consuming. Paper coated using a dip coating technique with chitosan and zinc oxide nanoparticles solution and utilized for cheese packaging [23].

2.2 Solution casting

Solution casting is a traditional method or technology for paper coating to improve paper-based packaging barrier properties. This method includes three steps: solution preparation, casting, and drying, as shown in Fig. 3 [12]. The casting of solution over the paper and proper coverage depends on temperature, the viscosity of the fluid, and the type of paper. The biopolymer solution is prepared, cast, or poured on paper and further dried. Drying time and temperature affect the quality and uniformity of the coated paper. The potato starch solution was successfully coated on paper using the solution casting technique, improving the paper barrier and mechanical properties. Water resistance increased by up to 25% and tensile strength by 178% [24]. The solution casting method has a wide range of biopolymer paper coating applications in food packaging. However this technique is a simple, low-cost method, but it has some limitations, which include a time-consuming process, paper coating being limited to the lab scale only, and requiring a longer time for drying due to high moisture content.

Fig. 3
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Schematic representation of the paper coating using the solution casting method

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2.3 Bar coating

Wire Bar coating is a novel technology for paper coating, also known as MeyerBar coating, a stainless-steel rod used for paper coating. A steel rod is a cylindrical bar with spiral wounds around it used to spread the solution over the paper, as depicted in Fig. 4 [25]. Pressure acts as the main factor for the thickness of the coating material. The amount of pressure we apply the coating of solution over the paper thickness and diameter or road also affects the smoothness and uniformity of the coated paper. The diameter of the rod is very as per the paper requirement. After coating, the paper is dried to evaporate the solvent. In this technique, multiwire and multi-bar help change properties. Glycerol beeswax solution is coated over the paper using bar coating, showing excellent uniformity and smoothness [26]. The chitosan solution was successfully coated on paper, which improved the barrier properties of the coated paper [27]. The hybrid coating is done on paperboard to enhance functional properties [28]. The wire bar method has wide applications in food packaging paper coating because it is a simple, low-cost, energy-saving method that makes it more effective for coating applications. Some of the limitations of bar coating are slow speed coating and the coated solution’s thickness depending upon the wire’s diameter.

Fig. 4
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Schematic representation of the paper coating using the bar coating method

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2.4 Novel coating methods

2.4.1 Spray coating

Spray coating is a novel method for paper coating in which molten micro-size particles come out through the spray nozzle and are deposited over the substrate. A non-contact coating process provides a micro-coating of dry powder and liquid on the paper surface using a high-pressure spraying nozzle [29]. The coating mix is sprayed on the paper surface, providing a multilayer uniform coating, as shown in Fig. 5 [30]. The method of applying liquid over the paper is known as atomization, which mainly depends upon nozzle characteristics and the number of nozzles. The nozzle spray angle controls the width of liquid coverage, and the pressure of the nozzle liquid affects uniformity coverage. Particle size, feed properties, and the coating mix’s viscosity affect the coating quality. Spray coating has wide applications and advantages, such as uniformity, waste reduction, and time-saving methods. Some of the limitations of this method are energy-consuming and costly. Wrapping paper was successfully coated with the spray coating method used in fruit and vegetable packaging [31]. Biopolymer solution, along with gelatin and enzymes sprayed on raw paper sheets, shows the application in beef packaging [32].

Fig. 5
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Schematic representation of the paper coating using the spray coating method

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2.4.2 Electrospinning

Electrospinning is the most recent advanced method for paper coating. This method keeps the biopolymer solution in the pump, and high-voltage electricity is applied to the solution [33]. Molten nanoparticles come out through the middle and are coated over paper, which provides high strength and a wide range of coating to paper, as depicted in Fig. 6. The electrospinning method of paper coating has three steps: solution preparation, melting, and coating, and three major requirements: high voltage, needle, and collector [34]. The molten solution comes from the pump through the needle in fiber from a collector or paper kept below for coating and uniformly deposited over the paper surface. The solvent used in the solution evaporates while coming out through the middle. Electrospinning is a simple, environment-friendly method that provides many biopolymers for paper coating. Biobased compound proteins, cellulose, and polysaccharides have a wide range of applications in paper coating with electrospinning. Paper coated with electrospinning shows superhydrophobicity and better food packaging [35]. Cellulose paper was coated with biosource by electrospinning, and electrospraying shows excellent potential in utilizing food waste for the ultra-thin coating to reduce food waste [36]. High precautions are needed while using this coating method. The amount of voltage regulates the size of producing fibers; the solvents used are harmful and must be handled properly. The electrospinning method of paper coating is limited to lab-scale and can be modified after study for industrial-scale paper coating. The electrospinning method has great potential in paper coating research and is needed in some areas to improve the properties of nanofibers.

Fig. 6
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Schematic representation of the paper coating using electrospinning coating method

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3 Reinforcement of paper to improve barrier properties

Barrier properties of paper control the shelf life, sensory characteristics, and nutritional value of food products. Water barrier, gas barrier, and oil resistance are some of the critical barrier properties of packaging paper. Water barrier properties include water vapor permeability and water vapor transmission rate [37]. The standard ASTM F1249 and BS 7406 methods determine the water vapor permeability rate. Gas barrier properties are oxygen permeability and oxygen transmission. The M D-3985, ASTM F-1927 method can determine the oxygen permeability rate. Chitosan, corn starch, polylactic acid, cellulose, polyvinyl alcohol starch, protein, lipids, and polysaccharides are some biopolymers used in paper coating to enhance barrier properties [38]. The effect of bio-sourced coating material on water vapor, oxygen, and oil barrier properties on paper are summarized in Table 3.

Table 3 Reinforcement of paper coating to improve water vapor permeability, mechanical, oxygen, and oil barrier properties
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Kraft paper is coated with citrus (mandarin) fruit peel and leaf extract, wherein the paper coated with mandarin leaf shows a higher hydrophobic nature than the paper coated with mandarin peel [39]. Paper coated with a higher amount of coating material shows a smaller value of water vapor permeability than paper coated with a lower amount of coating material as the amount of coating solution fills pore spaces in the paper and from a strong layer over the paper surface, which restricts the transmission of water vapors. Paper treated with peel-leaf extract shows much better gas barrier behavior than paper treated with only peel extract [39]. Paper coated with regenerated cellulose (cotton linter) solution and tensile strength of paper increased by 6% and 2% reduction in oxygen permeability; if the cellulose percentage increased by 2%, the gas barrier increased by 33%, and the water barrier by 19% of paper also increased due to the formation strong hydrogen bond and compact structure of paper fiber [40]. As per the study by Wang [16], calendared paper coated by cellulose stearoyl easter solution with different coating grammage. Cellulose esters are hydrophobic, as coating grammage on paper increases the roughness of paper, and the contact angle of coated paper decreases. The barrier properties of coated paper are higher than that of control paper. The uncoated paper shows a zero-degree contact angle while five coated paper shows 109 ± 2°, 106 ± 2°, 105 ± 2°, 101 ± 1°, 102 ± 2°, and 99 ± 3° as coating grammage increases contact angle slightly decreases. WVTR and WVP of 84.93 ± 6.25 g m−2 d−1 and 0.61 ± 0.01 × 10 −8 g m−1 s−1 Pa−1, more than uncoated paper [16].

Carboxymethyl cellulose/cellulose nanocrystals solution is coated on paper and water vapor permeability of paper was found to be 8.75 × 10−10 g·m/m2·Pa·s due to the coating of solution, pores of paper are reduced so permeability decreases while uncoated paper having WVP 11.74 × 10−1g·m/m.2·Pa·s. This is due to coating solution from the matrix, filling up the pores in the paper, and increasing the effective chain length coating of the solution, which improved the gas barrier properties of paper and showed excellent potential in strawberries and food packaging applications [41]

Paperboard coated with polysaccharides shows low oxygen and water permeability, but it needs some chemical modification with biopolymer barrier properties of the paper board, which will have a great impact. Starch glycerol film barrier properties can be improved by compounding with polycaprolactone [42].

Paper coated with wheat gluten coating solution and filled porous structure significantly reduces the water vapor permeability of paper. Meanwhile, lower coating weight affects WVP more than higher coating weight. Wheat gluten very much improves the gas barrier penetration of paper. Coated paper results show wheat gluten has potential in food packaging applications [43]. Paper coated with Chitosan, glacial acid, and montmorillonite solution enhanced the oxygen barrier properties of the paper [16]. Montmorillonite forms a block structure when coated with chitosan-filled pores, which are found to form a continuous film with a robust fiber network. The coated paper shows improved water-resistant properties due to the hydrophobic nature of Chitosan [16]. Multilayer coating is done on paper with cellulosic pulps, micro-fibrillated cellulose (MFC), and nano-silica solution. Increasing the grammage of the MFC layer resists water molecules. It stops penetration due to nano silica, which increases the hydrophobicity of paper compared with uncoated paper. The formation of strong hydrogen bond gas barrier properties of paper increased coated paper having good WVTR and gas barrier properties [44].

The oil resistance property is one of the critical properties in paper food packaging for foods that contain fats and oils. Oil resistance directly affects the shelf life, taste, and structure of packed food items [38]. Paper coated with starch silver nanoparticles effectively increased the oil resistance property, and coated paper shows potential in fast food packaging [45]. As per a study by Chungsiriporn et al. [46], paper coated with carboxymethyl chitosan and sodium carboxymethyl cellulose solution enhanced the paper’s grease and oil resistance. It showed the potential of paper in multifunctional food packaging [46].

4 Reinforcement of paper to improve mechanical properties

Mechanical characteristics reveal the paper’s strength, allowing it to be used for suitable containers. Mechanical qualities depend on the base paper or the substrate compared to the covering layer. Tensile strength, burst strength, thickness, bending stiffness, basis weight, and heat resistance contact angle are crucial mechanical properties affecting packed food’s shelf life and storage [47]. The mechanical properties of packaging paper can be improved by biopolymer coating, giving sustainable and high mechanical strength to paper. The tensile strength of paper shows its strength, bonding, and fiber length. It is a property of paper resistance to breakage due to tension [48, 49].

Paper coated with silanized castor oil (SCO) and silanized methyl ricinoleate (SMR) shows improved mechanical properties. Paper coated with silanized castor oil having a tensile strength of 3.36 (N/m) and elongation at break (26.16%). Paper coated with silanized methyl ricinoleate has a tensile strength of 2.47 (N/mm) and elongation at break (21.89%). Tensile strength and elongation at the break of coated paper are higher than uncoated paper due to the condensation of the OH group of cellulose with the silanol group of resin on the paper surface, forming a strong Si–O–C network coated paper used for green packaging fruits and vegetables [21].

Raw paper sheet coated with biopolymer solution, transglutaminase enzyme, and citric acid. The tensile strength of coated paper slightly increased in the machine direction. In contrast, maximum elongation at break in the machine direction of two samples shows no difference compared to uncoated paper. The coated paper sample shows a decrease in elongation at the break due to lower film thickness. In the transverse direction, elongation at the break of coated paper significantly decreases. Paper’s mechanical properties (thickness and grammage) increased; however, there was a small increment in tensile strength [32]. Melanin nanoparticles, grapefruit seed extract, glycerol, and pectin powder solution coated on paper significantly improved mechanical properties and were used for banana packaging [50]. Wrapping paper coated with cassava starch modified by octenyl succinic anhydride enhances its tensile strength, folding endurance, and tearing strength in vertical and horizontal directions. Starch contains a hydroxyl group, which forms a strong hydrogen bond with the paper fiber network, and a continuous cellulose membrane, increasing the mechanical properties of coated paper [51].

Tang et al. [52] developed a paper using chitosan and titanium dioxide coating on cellulosic paper; its tearing and tensile strength increased. Uncoated sample paper measured tensile strength and tearing strength in machine direction was found to be 45.76 N m/g and 4.69 mN m2/g while coated paper tensile strength and tearing strength 51.16 N m/g and 5.26 mN m2/g. Titanium dioxide (TiO2) and chitosan dioxide (CTS) can be suitable agents to improve paper’s mechanical and physical properties as TiO2 and CTS nanoparticles are good enforcement agents and form strong bonds with the cellulosic fiber. Coated paper has potential in food and healthcare packaging. Paper coated with corn starch, silver nanoparticles, and alkyl ketene dimmer solution improved mechanical properties due to the formation of hydrogen bonds between the fibers and hydrophobic silver nanoparticles [53]. Paperboard coated with cassava starch, calcium carbonate solution, and polylactic acid solution also improve the mechanical properties in the machine direction than the cross direction [12].

Chitosan, bacterial cellulose, and ZnO solution coated on paper and mechanical properties of coated paper were found to improve tensile strength by 8.5%, tearing strength by 14.5%, and bursting strength by 16.5% on average. Cellulose nanostructure improves hydrogen bonding due to the high surface volume ratio. Coated paper is utilized for eco-friendly packaging [54]. The biopolymer cannot provide good mechanical properties when the alone coating is done and needs to blend with other materials to gain maximum results. Biopolymers used in paper coating are handled with precaution; there are chances of contamination and toxicity. Emerging technology improving paper mechanical properties helps in product storage, transportation, and shelf life.

5 Biobased reinforcement with antimicrobial capacity

Antimicrobial packaging is the leading technology in food packaging that helps keep food fresh and safe. Antimicrobial packaging reduces microbial and harmful pathogen growth, increasing the shelf-life of food products [55]. Paper packaging has several limitations on which work is to be done; the antimicrobial activity of paper is low, and adding antimicrobial agents can increase it. Figure 7 indicates (a) an illustration of the deterioration of the food product by microbes on uncoated paper. (b) Illustration of the non-deterioration of food product by microbes on the paper coated with antimicrobial activity.

Fig. 7
figure 7

Schematic representation of biobased reinforcement of antimicrobial activity. a Illustration of the deterioration of the food product by microbes on uncoated paper. b Illustration of the active protection of the food product from microbes on the paper coated with antimicrobial activity

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Antimicrobial agents are incorporated into food packaging paper through coating, direct addition, and encapsulation [56]. Polyvinyl alcohol, silver, copper, casein, enzymes, glucose, and chitosan are some of the antimicrobial agents investigated and can be used for paper coating to improve the paper’s antimicrobial properties [57]. A major challenge that antimicrobial packaging faces is the risk of health issues due to nanoparticle migration. Production and antimicrobial agent costs are higher, making this packaging method costly.

Raw paper sheet coated with 2% citric acid was observed to have microbial growth after 14 days of storage reduced to 1.98–3.09 log CFU per gram, and the antimicrobial property of the coated paper was much better than uncoated paper. Using organic acid reduces the growth of bacteria and increases the microbial capacity of paper. Coated paper is used for beef packaging [32]. Paper coated with nano-fibrillated cellulose, chitosan, and acetic acid solution has shown antibacterial activity against gram-positive and gram-negative bacteria was studied. Chitosan-coated paper inhibits bacterial growth through electrostatic interaction between its protonated amino groups and negative residues on microbial cell membranes. Chitosan, having low molecular weight, strongly increases the ability of paper and reduces the growth of bacteria. Chitosan having a molecular weight of 25 kDa shows a more antimicrobial effect than chitosan with a 2500 kDa molecular weight [27].

Solution of PBAT poly(butylene adipate-co-terephthalate), zinc oxide nanoparticles, and grapefruit seed extract were prepared and coated on kraft paper using coating bars. Paper coated with zinc-oxide nanoparticles and PBAT solution reduces foodborne pathogen bacteria E. coli from 6.5 CFU/ml to 0 in 6 h; it shows a reduction in L. monocytogenes from 6.7 to 5.6 CFU/ml and 4 CFU/ml in 6 and 15 h. ZnO nanoparticle activity mainly enhanced the antimicrobial activity of kraft paper. Coated kraft was used for fruit, vegetables, and high moisture-content food packaging (Shankar & Rhim, 2018). Filter paper coated with Cu metal–organic frameworks (CuMOFs) nanoparticles with polydimethylsiloxane (PDMS) treatment. The coated paper shows excellent antibacterial activity against E. coli compared to S. aureus due to a thick layer of S. aureus wall resisting the entry of Cu ions. Coated paper has hydrophobic and antibacterial activity [59].

Kraft paper coated with Chitosan, bacterial cellulose, and ZnO solution enhanced the paper’s antibacterial activity. The chitosan-coated paper shows a 96.36% reduction in E. coli and a 100% reduction when coated with chitosan bacterial cellulose and ZnO composite. Antimicrobial assay results show that ZnO and chitosan shape and size do not affect the antibacterial activity of coated paper. Prepared solutions and coated paper show potential in food packaging applications [54]. Antimicrobial packaging has great potential to provide the safety and quality of food products by reducing the growth of harmful microorganisms and pathogens. Rare bioavailability of bio-based antimicrobial agents and loss due to high-temperature treatment is an area of research and study that will fulfill the demand for biobased packaging [60].

6 Bioactive reinforcement with antioxidant capacity

Antioxidant active packaging is the leading packaging method in which an antioxidant compound is incorporated into a polymer matrix and can be coated on the surface of packaging material, which absorbs or releases active compounds that help to stop lipid oxidation and increase the shelf life of food products [17]. Oxidation and antioxidant reactions affect the color, texture, nutritional value, and taste of food products (Fig. 8). With the increasing demand for sustainable packaging, various biosources are used as antioxidant agents in paper packaging. The antioxidant capacity of paper can be improved by coating, incorporation, and direct addition of antioxidant biosource compounds; there are various coating and incorporation methods. Solution casting, wire bar, coating, and dispersion methods are widely used to prepare antioxidant-based paper for food packaging [61]. High temperature and pressure treatment can affect and reduce the biosource antioxidant activity. Biosources containing flavonoids, phenolic acids, carotenoids, tocopherol, vitamins, and anthocyanins are used in paper coating to increase the antioxidant capacity of paper. Thiobarbituric acid (TBA) and DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate methods are used to measure the oxidation rate and determine the antioxidant activity capacity [62].

Fig. 8
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Representation of a oxidation mechanism before the coating of the paper b antioxidation mechanism after coating of paper consisting of antioxidant agents in food applications

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As per a study by Battisti et al. [32] paper used for beef packaging and coated paper shows 0.17 ± 0. 01 and 0.07 ± 0.01 mg of malondialdehyde kg−1 while uncoated control paper shows 0.23 ± 0.03 mg of malondialdehyde kg−1 [32]. Malondialdehyde determines the rancidity in meat, the TBA method was used to measure the level of Malondialdehyde. Citric acid is an antioxidant agent, prevents lipid oxidation, and increases paper’s antioxidant capacity. A kraft paper was coated with soy lecithin, lemongrass essential oil, and palm wax solution; antioxidant activity and total phenolic content of coated paper increased, and peptides present in solution content controlled and reduced the rate of lipid oxidation. Coated paper can be used for meat and poultries packaging, increasing food products’ shelf life [63]. As a major antioxidant agent, mandarin fruit peel and leaf extract containing terpenes show greater antioxidant activity, stop oxidation rate, and extend food products’ shelf life. Paper coated with peel and leaf shows higher scavenging activity than sample paper coated only with peel [39].

Kraft paper coated with acetylated cellulose solution; the radical scavenging capacity of coated paper was found to improve due to the addition of cinnamaldehyde (CIN), which controls the antioxidant capacity of coated paper. A total of 6% of CIN-coated paper shows excellent antioxidant activity, and coated paper is used for beef and fat food packaging [64]. Antioxidant agents proved that they can act as a barrier to stop the reaction with oxygen and protect food from deterioration. Further development and research are needed to improve and increase biosource antioxidant agent efficiency for sustainable bio-based food packaging [65].

7 Smart material/safety indicators

Smart packaging is also known as intelligent packaging. It is an advanced food packaging technology that senses and monitors the inside and outside temperature of food products and provides information about the safety and quality of food [66]. Smart indicators are used to monitor food products in real-time conditions. Temperature, Oxygen, Carbon dioxide, and freshness indicators are available that sense and indicate the condition of food products [67]. Bio paper-based indicators have great potential in intelligent packaging. Polysaccharides, proteins, cellulose nanocomposite, and starch contain a natural pigment that can be utilized in innovative paper packaging [68]. Natural indicator agents available are anthocyanin, carotenoids, chlorophyll, curcumin, betaine, etc. [69]. These natural and bioderived pigments are coated on paper surfaces using the new coating technique to develop paper-based smart indicators for food packaging applications.

A coated paper used for real-time freshness monitoring of packaged fish. As the deterioration of the fish started, the pH decreased, and the indicator’s color started changing from yellow to purple. The starting measured pH was 5.20, and the indicator’s color was yellow. On the 9th day, pH was found to be 3, and the color was purple. Coated paper has potential in smart packaging for meat and fish products [70]. Bromothymol blue (BB) and methyl red (MR) solutions were prepared, and indicator film was prepared on filter paper. The prepared indicator was used to determine the quality of bell paper starting from day 0. The color of the indicator was yellow-green as pH changes; spoilage started after 7 days, and the color of the indicator changed to orange. Prepared indicators show effectiveness at different temperatures; most tests were conducted on fresh fruits and vegetables [71]. Deacetylated chitosan, Tetraethylorthosilicate (TEOS), and Zinc oxide (ZnO) nanoparticles solution was prepared and anthocyanin was added to solution, extracted from black carrot, the prepared solution was coated on Whatman filter paper by dip coating and indicator was prepared. The indicator used in the milk packaging’s initial pH was 6.6, and the color was blue. After 48 h. The color indicator changed to violet rose, indicating milk spoilage. The pH of milk was found to be 5.7. Anthocyanin acts as the primary agent in the color response prepared indicator to help indicate pasteurization quality [19].

Cellulose paper was coated with starch-alizarin and glycerol solution by a dip coating method, and a pH-based indicator was prepared. The indicator was utilized in fish packaging. The indicator’s color changes from yellow to purple as spoilage starts, and the pH changes from 6.67 to 8. Alizarin solution shows a sensitive response and eco-friendly smart fish packaging [72]. The advantages of additives used for smart and safety indicators include low-cost, recyclable, renewable, and safe natural colorants used in smart packaging to replace traditional synthetic dyes that are harmful to health. Bio additives show no harmful effect on human and product quality as the migration rate is low. Some of the limitations that biobased additives face are low miscibility and thermal and light stability, which affect developed smart material performance in different storage environments. Some of the additives significantly affect the paper’s coating strength. However, future research is required to overcome these limitations and produce highly effective paper-based smart indicators with improved properties for food packaging applications [73].

8 Application in food

Paper packaging has become the most promising approach to overcome pollution due to the traditional method. Paper coating is the method to overcome the limitation of paper’s physical, mechanical, and gas barrier properties [74]. Various paper coating methods with bio-sourced materials were used to enhance paper properties and are utilized for food packaging, as their form of application is presented in Fig. 9. The coated paper has been used for fruit, vegetables, meat products, snacks, and confectionery packaging [75]. Coating biopolymers per the safety and regulatory standards given by the Food and Drug Administration (FDA) regulatory authority can fulfill the demand for sustainable food packaging applications [76, 77]. Filter paper coated with pea hull and sodium carboxymethyl cellulose solution using solution immersion technique coated filter paper shows improved barrier, thermal properties, and reduced moisture migration rate. After seven days, coated silver nanoparticles exhibit excellent antibacterial activity in coated filter paper used for fresh strawberry packaging. The result shows that coated paper maintained the freshness of strawberries under ambient conditions. Coated filter paper has the potential for active and green packaging of fruits and vegetables [41].

Fig. 9
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Applications of coated paper and paper-based packaging in food products

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Kraft paper coated with Grapefruit seed extract (PBAT) poly(butylene adipate-co-terephthalate, zinc nano-oxide solution using wire bar of the coating method. Grapefruit seed extract and PBAT solution improve the antibacterial activity of Paper against L.monocytogens, while Paper with PBAT and ZnO nanoparticles shows strong antibacterial activity against L.monocytogen and E. coli. Coated kraft paper can be used to contain high moisture content and to package frozen foods. Paper-improved antimicrobial properties give them potential applications in food packaging [58]. Cellulosic paper is coated with chitosan and nisin solution using the dip coating. The addition of nisin increased the antimicrobial activity of the paper. The coated paper was used in cheese packaging for 14 days, and it was analyzed that the cheese shelf life of the sample increased [23]. A mixture of soybean hull, bentonite, and bromocresol purple was coated on filter paper using a rod coater. The coated paper was used for real-time monitoring of catfish filets for 10 days at 4 \(^\circ{\rm C}\). As the deterioration of food products starts, the paper color changes and the freshness of food gets determined. Coated paper fish packaging investigation shows that pH-based indicators can be used for various food applications and reduce food wastage [70]. Cellulose paper coated with chitosan and alizarin was utilized in the real-time freshness indicator of minced fish [72]. Coated paperwork as pH-based indicators gives information about product quality to the customer. Coated paper has the potential of smart food packaging. Green bell paper shelf life was studied and improved when packaging was done on coated filter paper. The filter paper was coated with methyl red and bromothymol blue solutions, and the coated paper showed the microbial growth color of the paper changed from yellow-green to orange when the bell paper deteriorated. Coated filter paper has applications in the smart packaging of fresh fruits and vegetables [71].

Kraft paper was coated with gelatin/palm wax/lemongrass essential oil (GPL) solution using the solution casting method. Beef shelf life was studied under different paper packaging, unwrapped sample, uncoated paper with the sample, paper coated with gelatin–palm wax, and paper coated with gelatin, palm wax, and lemongrass essential oil; the sample was kept for 7 days. Paper coated with GPL solution shows better active, antimicrobial, and antioxidant properties than other paper and controls microbial growth, increasing the shelf life of beef. GPL-coated kraft paper shows potential in the active packaging of food material [63].

9 Conclusion

Paper-based food packaging has gained demand as it offers human safety and environmentally friendly food packaging solutions. However, paper-based packaging materials have constraints and challenges related to reduced mechanical properties, gas barriers, moisture mitigation, and active properties. The coating and incorporation of bio-sourced materials with paper can successfully overcome the challenges of paper-based food packaging material and maintain the product’s shelf life. Novel coating methods, such as spray and electrospinning, are the new merging industrial-scale paper coating methods that can fulfill the demand for functional properties. The low energy requirement, low cost, and biodegradability make the coating technique promising for novel food packaging. Starch, protein, cellulose, and lipids are the natural coating materialthat improves the properties of packaging paper and is capable of being used in food packaging, having no adverse effect on human health. Reinforcement of this biopolymer into packaging paper matrix has improved physical properties, increased mechanical strength showing durability, and resistance to tear, which allows protection of the product. The gas and water barrier properties have been improved with the coating, showing moisture and gas migration from the outside environment to a food product being reduced, protecting food from the off-flavor, oxidative damage, etc. The antioxidant and antimicrobial activities of food packaging grade paper have been improved with the incorporation of active bio-derived functional compounds. The coated paper protects food products from microbes and provides added functionality. Novel coating methods and biobased compounds make the paper suitable for smart food packaging, producing real-time product information for consumers. With improved paper properties, food industries have shown a range of food product applications, including bakery, confectionary, snacks, fast food, fruits, etc. Mass-scale production and time-consuming processes are significant challenges for a paper coating that needs further research. The future production process of paper-based packaging materials will require developing economically viable processing techniques. This will increase the use of plastic-free packaging materials in the food business while lowering the need for fossil fuels and enhancing environmental sustainability. Further, more research is also required on the interaction of different coating materials with types of paper and its migration in specific food products.