Pectin and Its Applicability in Food Packaging

Abstract

Food packaging based on plastic films made from nonrenewable resources often causes environmental problems after disposal. Recently, researchers are increasingly focusing on alternative materials to reduce the use of nonbiodegradable and nonrenewable films. Generally, biomaterials are nontoxic, biocompatible, and renewable always presents reasonable film-forming ability. Thus, they are important for food safety, where undesired chemical compounds might migrate from chemicals migrate from the plastic packaging materials into foods. Pectin (PEC), as a natural carbohydrate polymer, belongs to the anionic heteropolysaccharide family and is often extracted from various residues from plant food processing, such as apple and citrus pomaces. The pectin molecules are highly branched with a backbone α-(1–4) linked D galacturonic acid. Among the naturally derived carbohydrate-based biopolymers, pectin was considered a promising substrate in fabricating edible films due to its diverse advantages, such as perfect film-forming ability, evidenced bioactivity, easy availability, and excellent quality biodegradability and biocompatibility, nontoxicity, and low cost. Pectin-based films have excellent oxygen barrier capacity and extend the shelf life for different fruits. The properties of pure pectin films can enhance through combination with other polymers or nanoparticles/fibers.

1. Introduction

Packaging plays a fundamental role in all our daily lives purposes, especially in food industries for food products (fruit and vegetables) during post-harvest and processing due to their different uses, such as; 1) Separate the food from the surrounding environment, 2) Preserving food quality, and safety, 3) Protecting from the spoilage factors, 4) Maintaining the nutritional value of products, 5) Extending shelf life, and 6) Provides information about the products for the consumers [1, 2, 3]. The packaging process was defined as the art, science, and technology to deliver the different goods to the consumers at economical prices, securely, and high quality [4].

Fossil fuels (include coal, petroleum, natural gas, oil shales, bitumens, tar sands, and heavy oils) are considered the main source for commercial polymers used in food packaging and producing plastic packaging [2, 5]. This is due to several reasons, such as ease of processing, low cost, lightweight, high energy effectiveness, and flexibility. The use of plastic packaging increases worldwide, owing to increasing population growth, which leads to increasing demand for processed food [6, 7, 8]. The plastic packaging production reached 380 million metric tons worldwide, approximately 60% of all plastic packaging used for foods and beverages, and the remainder covers nonfood applications [9].

Despite the different advantages of plastic polymers, it considered highly hazardous due to containing a large variety of chemical additives which using during manufacturing; thus, it has a severe threat to consumer’s health and environmental pollution [10, 11, 12, 13, 14, 15] such as 1) Produce a large of wastes which can be toxic to biological life [16, 17, 18]. 2) Migration might result in accumulation of undesired chemical compounds from packaging materials to foods, such as Bisphenol A (BPA) [12, 19]. 3) Lead to toxic and harmful effects on wild and human life because it is nonbiodegradable and not reusable [6, 20, 21].

In 2015, global plastic waste volume reached around 6.3 billion metric tons and is expected to increase to 12 billion metric tons by 2050 [22].

Therefore the food industry has classified the conventional plastic packaging material as a source of pollution and social concerns due to its nonbiodegradability and poor waste management, due to the accumulation of huge amounts of plastic waste in the environment, and also rapid depletion of fossil reserves and increases in the cost of petroleum, the food packaging industry toward the development and application of eco-friendly materials and biodegradable materials [23].

Various technologies have been used in food packaging to preserve the fruit and vegetable’s quality and safety and prolong their shelf life, such as ultraviolet irradiation, ozonation, changed atmosphere, and biodegradable films [24]. Edible packaging is considered a promising alternative and received much attention to tackle the plastics packaging problems [25, 26, 27].

Production of environmental-friendly packaging such as biodegradable and renewable films represents an interesting alternative to conventional polymers. Polysaccharides and proteins address those requirements because of their desirable film-forming properties, and, as most of them are also edible, they can be used as edible films and coatings. Edible films and coatings can extend the shelf life of food products by improving the mechanical properties and reducing the transfer of moisture, lipids, flavors, or gases between the food and the surrounding environment [17]. Edible coatings modify the atmosphere around fruit and/or vegetables, altering oxygen levels inside the fruit, retarding the production of ethylene and thus, limiting the physiological decay of fruits; This also reduces the ripening-induced quality degradation in terms of texture or loss of bioactive compounds during storage [28].

Edible coating materials efficiency and performance depend on i) Properties of coating materials (type, concentration, viscosity). ii) Methods of coating (dipping, spraying, and dripping) [29, 30, 31]. A coating with excellent barrier and poor mechanical properties, bad flavor, or high cost will not be of commercial interest for using, and selecting a proper coating for the fruits also is not easy. So, it is necessary to study the film’s physicochemical and structural characteristics [32, 33].

Pectin as edible films/coating used to increase food quality and extend the shelf life of food products which is considered an alternative to packaging materials from synthetic polymers, thus preventing environmental pollution from nonbiodegradable plastic materials [34].

Younis and Zhao [35] reported that pectin polymers are considered promising polysaccharide biomaterials in developing eco-friendly films due to their film-forming, biodegradable, and nontoxic characteristics.

2. Pectin

Pectin (PEC) is a natural polymer and complex anionic heteropolysaccharides [36, 37, 38, 39], consisting mainly of α-(1-4) linked D-galacturonic acid residues and neutral sugars, which are partially esterified with methyl alcohol or acetic acid at the carboxylic acid [37, 40].

Pectin is a family of plant polysaccharides accounting for up to 35% of primary cell walls in certain species. It has been considered the most structurally complex polysaccharide in nature. The term “pectin”, in fact, describes a group of oligosaccharides and polysaccharides that share common features but are highly diverse in their fine structure, except that they all comprise at least 65% galacturonic acid (GalA), which is linked at the O-1 and O-4 position [41].

Zhou et al. [36] noted that the pectin polymer consists of three polysaccharide domains: Homogalacturonan (HGA), Rhamnogalacturonan-I (RG-I), and Rhamnogalacturonan-II (RG-II), where Homogalacturonan (HG) considered the most abundant cell wall pectic polysaccharide, about 50–90% of total pectin, meanwhile rhamnogalacturonan I (RG-I) is the second most abundant type comprising between 20% and 35% of total pectin [42, 43].

Pectin is a white, amorphous, and colloidal carbohydrate of high molecular weight occurring in ripe fruits, especially in apples, currants, etc., and used in fruit jellies, pharmaceuticals, and cosmetics for its thickening and emulsifying properties and ability to solidify to a gel. These properties and applications have put pectin in the biopolymers market with great potential for future developments [44].

2.1 Pectin sources

Several studies have documented that pectin is one of the most abundant polysaccharides in the primary cell wall and middle lamella of all plant tissues [39, 45]; the pectin production comes from two ways i) Commercial pectin comes from citrus fruit peels [46, 47], apple pomace [47, 48] pomegranate peels [49, 50], mango peel [3, 51], lemon peel [52], sugar beet pulp and potato pulp [3, 51]; ii) Noncommercial pectin obtained from cocoa husks [53], mulberry branch bark [54], peach pomace [42], sisal waste [42], pumpkin [51], banana peel [55, 56] watermelon rind, and soy hull [38].

2.2 Pectin extraction

There are different techniques for pectin extraction which is considered highly efficient and eco-friendly such as conventional solvent extraction based on stirring and heating; microwave-assisted extraction (MAE); ultrasound-assisted extraction [57, 58]; subcritical water extraction, and enzyme-assisted extraction [59], each of them has advantages and disadvantages.

Wicker et al. [60] noted that the pectin polymer could easily be extracted using different acids by conventional heating extraction. It consumes more time, the hot solution leads to pectin degradation, produces a large volume of effluent, and causes environmental pollution concerns. The MAE method is considered an excellent alternative to conventional extraction methods and offers significant advantages 1) Requires shorter processing times and less solvent, 2) Higher extraction rates, 3) Low in cost [52, 59].

The microwave-assisted extraction method (MAE) has been reported as the preferred extraction method of pectins from natural sources such as dragon fruit peels, bagasse, and pomace obtained from Mexican lime fruit, pomelo, mango, and papaya peels under different operation conditions. MAE conditions are dependent on different factors, such as microwave power, pH, time, and S:L ratio. MAE methods show significant advantages over conventional extraction techniques, such as reducing the amount of the extraction solvents, low energy consumption, high recoveries, good reproducibility, short extraction times (minutes rather than hours), and minimal sample manipulation [44].

The percentage of galacturonic acid group of pectin is esterified using methyl, or acetyl groups are termed the degree of esterification [61]. According to the degree of esterification (DE), PEC is commonly categorized into: High methoxyl pectin (HMP) (DE > 50%), and low methoxyl pectin (LMP) (DE < 50%) [57, 62, 63]. The degree of methyl-esterification can be defined as the percentage of carboxyl groups esterified with methanol of the pectin or the number of moles of methanol per 100 moles of galacturonic acid [64].

Pectins are usually extracted by hot dilute mineral acids at pH 1.5–2.5, taking 2–4 h with further precipitation with ethanol or isopropyl alcohol, separation to remove impurities, drying, grinding, and blending with other additives. The extracted pectins can be categorized into two major types, depending on their DM degree, and different factors like pH, temperature, time, and solvent: liquid (S:L) ratio are usually studied to optimize the extraction conditions [44].

Valdés et al. [44] showed that the different natural pectins extracted by solvent extraction methods; such as tomato, banana peel, and sugar beet, the tomato peel pectin can be extracted through two steps by ammonium oxalate and oxalic acid at 90°C (24 and 12 h) and pectin yield extraction (PYE) of about 32.0%, while Sugar beet pulp pectin produced by citric acid, pH 1, 166 min at 99°C, 1:20 g·mL⁻¹ 23.95%. Banana peel using a citric acid solution with pH 2.0 at 160 min, 87°C, 1:20 g·mL⁻¹ give a lower PYE 13.89%, the PYE can be increased to 16.54% using citric acid and HCl, pH 1.5, 4 h, 90°C, but the pectin from mango peel can extract using sulfuric acid in water with pH 1.5, and 2.5 h at 90°C which give a higher extraction yields about >70%.

The HMP and LMP pectin have different physicochemical characteristics and thus different applications for each of them [53]; therefore, the degree of esterification plays an important role and is a good parameter for the biochemical, physical properties of pectin applications [16, 65]. Cho et al. [66] reported that the HMP pectin could be converted into LMP using two ways: 1) Chemical de-esterification by alkali; 2) Enzymatic treatment by pectin methylesterase. The LM-pectin is mainly produced by the chemical de-esterification of HM-pectin with acid, alkali, and alcoholic/aqueous ammonia [67].

Depending on the raw material and the extraction method, pectins have various molecular weights, structures, and functional groups. These characteristics influence and determine the techno-functional properties of pectin molecules, such as gelling properties [43].

However, the industrial production of LM-pectin by enzymatic de-esterification of HM-pectin remains a challenge. For successful industrial application, it is necessary to enhance pectin methylesterase (PME) productivity by genetic modification and optimizing culture conditions [67].

2.3 Properties and advantages of pectin

Several studies have reported that the pectin polymers have several properties and advantages such as renewability, biodegradability, and biocompatibility [20, 68, 69], amphiphilic properties (hydrophobic/hydrophilic nature) [48, 49], pectin-based films showing high tensile strength, and water resistance [70], but the applications of pectin is limited due to their poor chemo-physical properties and has poor water barrier properties if it used alone [3, 71]. Younis et al. [34] noted that the pure pectin films encountered several defects when used alone without any other polymers, such as soluble in water, high water permeability, poor waterproof, and unsatisfactory mechanical properties. These defects heavily limited the application of pectin films, especially in an atmosphere with high humidity or to package high-moisture foods.

2.4 Pectin applications

Pectin is considered a good source for human health, where its consumption by large volume in our life due to its ability to decrease blood cholesterol levels [37, 42, 51], and has been widely used in the food and nonfood industries; 1) Food and beverage industries, as edible films [3], gelling and thickener, texturizer [39, 49, 72], emulsifier agent [38, 49], colloidal stabilizer in food products such as jams, yogurt drinks, dairy products, and ice cream [51, 72, 73], also carrier polymer for the encapsulation of food ingredients [74]. 2) Pharmaceutical and biomedical applications [51, 75], including drug delivery, gene delivery [69], cosmetics [39], wound healing, and tissue engineering hydrogels as carriers for tissue regeneration [68, 76].

3. Pectin in food industry and food packaging

For the food industries, several studies showed that the pectin has an excellent potential to be an edible film for food packaging and biocomposite materials [3, 20]; the presence of methoxyl groups in the pectin structure leads to an increase in the hydrophobic nature of pectin molecules that help the pectin to use in different food applications such as emulsifier agent and stabilizer [48]. The gels from the HM pectin are formed under sugar or acidic conditions, while from LM pectin formed through ionotropic gelation with low-valence ions, such as calcium ions, due to its containing a large number of ionizable carboxylic groups; therefore, they have a strong affinity for calcium ions [68], where the carboxyl group linked with the D-galacturonic acid residue exists in two essential forms: 1) carboxylate salt; 2) neutral methoxylated or ester [77]. Natural hydrocolloid pectin is widely utilized for thickening, stabilization, and encapsulation in the food & beverage, cosmetic, and pharmaceutical industries [67].

Pectins are hydrocolloids typically used as thickening and gelling agents, e.g., sauces and jams [43]. The use of pectin as a thickening and gelling agent, for example, sauces and jams, also gaining interest as a potential food emulsifier of natural origin; it can be used as a multifunctional ingredient in different food applications [78]. Einhorn-Stoll et al. [79] found that citrus pectin can be used as a thickening and gelling agent in a wide range of foods. At the same time, Liu et al. [80] showed that the pectin produced from sugar beet pulp (SBP) is the most prominent for stabilizing oil-in-water (O/W) emulsions and has received increasing attention in the food industry as a polysaccharide-based emulsifier.

The most recent trends in the field of pectins coating applications include; the shelf-life extension of fresh-cut highly perishable food, the application of pectin coatings as a pre-frying treatment to reduce the oil consumption in deep-fat fried products, and the use of pre-dried treatments to improve the retention of nutrients and quality characteristics of dehydrated and lyophilized food [44].

Due to its biodegradability, biocompatibility, edibility, chemical and physical properties, pectin is considered an applicable polymeric matrix for elaborating edible films intended as active food packaging [40]. Pectin-based biofilms could extend the shelf life of avocado fruits over a month compared to uncoated fruits by decreasing the oxygen absorption and thus delaying texture and color change [81].

Sucheta et al. [82] noticed that the performance of the commercial pectin films was affected by the incorporation of cornflour and beetroot; significant differences were found in tensile strength (TS), water solubility (WS), and the thickness film, where the TS increased when the pectin added to cornflour and beetroot from 1.36 to 7.47 MPa and 3.79 MPa. The WS decreased from 97.8% to 70.7%, also decreased film thickness from 0.24 to 0.06 mm and 0.09 mm, respectively. The effect of pectin with cornflour and beetroot as a coating has been studied of tomatoes fruits by Sucheta et al. [28] and find that the best coating for tomatoes was pectin/cornflour, it showed a significantly reduced the weight loss %, also delayed the respiration rate with retention of internal quality during the storage period (30 days) improved the shelf life of tomatoes and showed minimum shrinkage during the end of storage.

Meerasri and Sothornvit [83] find that the pectin polymer could provide a combination with a plasticizer (glycerol) and bioactive compounds (Gamma-aminobutyric acid [GABA]) and affect its performance; GABA incorporation showed an excellent enhancement in the barrier water than the glycerol addition where the WVP for the pectin decreased from 3.59 × 10⁻¹⁰ to 2.54 × 10 g⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹ (pectin/GABA). In contrast, the glycerol incorporation led to increasing the WVP to 3.73 × 10 g⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹, the mechanical properties of pectin films were significantly affected by glycerol and GABA incorporation, the TS for the pure pectin film 6.41% decreased to 2.14 and 2.17% for glycerol and GABA, respectively, while the Elongation at break (EB) increased from 8.78 (pectin film) to 15.11 and 27.99 MPa, respectively.

Sucheta et al. [28] studied the effect of pectin-corn flour-based coating and observed that it was the best treatment that reduced weight loss and decay, delayed respiration with retention of biochemical quality, and improved the shelf life of tomatoes.

Chitosan/poly (vinyl alcohol)/pectin ternary film was prepared by solution casting method; the films showed the antimicrobial activity against different pathogenic bacteria, such as Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Pseudomonas spp [84].

Lorevice et al. [85] studied the effect both of HMP (High methoxyl pectin) and LMP (Low methoxyl pectin) with chitosan nanoparticles (DD = 94%) as edible films using water as solvent and find that the addition of chitosan nanoparticles (CSNPs) to pectin films did not cause remarkable visual changes but improved the mechanical and physical properties when compared with pure pectin films as a result of stronger interactions between the polymer matrices; The pure LMP films recorded a lower values than HMP films for the thickness and the mechanical properties, where the thickness, Elongation at break (EB) and Tensial strength (TS) of pectin films was remarkably increased after the addition of CSNPs; For the TS increased from 30.81 MPa to 46.95 MPa for HMP pectin films; whereas LMP films increased from 26.07 MPa to 58.51 MPa, the EB recorded a higher value for the LMP/CSNP 2.91% compared with pure LMP pectin (0.94%), the enhanced in the EB values of LMP films incorporated with CSNPs may be explained by the higher number of interactions between this pectin and CSNP surface, where it has more carboxylic groups that interact with CSNP amine groups.

The thermal properties performed by differential scanning calorimetry (DSC) analysis and noted that the heat absorbed (ΔH, change in enthalpy) by pectin films was larger than by pectin powder and PEC/CSNPs films where it increases from 401.6 → 444.7 → 547.9 J·g⁻¹ for HMP powder, HMP films and HMP/CSNP film, respectively. Regarding the endothermic peak temperatures (EPT) property, it decreased when CSNPs were added from 121.8 → 105.1 → 105.9°C for HMP powder, HMP films, and HMP/CSNP film, respectively. Also, for the LMP, the EPT decreased from 108.9 → 97.8°C, for LDM pectin powder, LMP films, respectively, while by the CSNP addition, the temperature increased to 102.1°C. this can be attributable to reduced natural hydration degrees of pectin films due to CSNP presence, the lower hydration degrees may result in lower chain mobility, the lower EPTs, and higher ΔH values suggest that CSNPs were occupying water sites within pectin matrices and led to absorb more thermal energy than pure pectin films.

For the barrier properties, the addition of CSNPs into the LMP films made a significant difference and decreased the water vapor transmission rate and permeance property from 118.67 to 96.56 g·h⁻¹·m⁻² and 81.04 to 54.06 g·kPa⁻¹·h⁻¹·m⁻², respectively, the effect of reducing permeance caused by CSNP presence was more remarkable than in HMP since LMP has a higher content of free hydroxyl groups than HMP [85].

Ngo et al. [86] evaluated the films from pectin (2% w/v) and nano chitosan (2% w/v) with different ratios (100:0, 75:25, 50:50, 25:75, and 0:100 w/w) and find that the blending ratio 50:50 increased the tensile strength and decreased the water solubility, water vapor permeability, and oxygen permeability; Also, these films showed antimicrobial activity against C. gloeosporioides, S. cerevisiae, A. niger, and E. coli.

Ranganathan et al. [87] noted that pectin polymer has the great potential to form a polymer composite and makes it flexible film due to its anionic property, whereas; Tsai et al. [88] found that the addition of pectin into chitosan with a high degree of deacetylation increased the viscosity of the matrix solution, and making it more difficult to prepare homogeneous solutions; also mentioned if the densities of positive charges on the polycations and negative charges on polyanions are not equitable, the solution will be water-soluble and form homogeneous.

Chen et al. [89] showed that when chitosan was mixed with pectin, the mechanical properties and hydrophilicity increased for the chitosan/pectin films, where they prepared the chitosan/pectin membranes successfully via using a freeze-gelation method and proved that the combination of pectin into chitosan could significantly enhance the properties of the film including and increased the tensile strength from 8 N·g⁻¹ (CH films) to 32 N·g⁻¹ (CH: PEC films) also decreased the water contact angle from 85^○ (CH films) to 45^○ (CH: PEC films); therefore it can be used as a carrier for food or drug.

Norcino et al. [16] used the low molecular weight chitosan with the degree of deacetylation of 80% and pectin from the peel of citrus fruits to prepare different CH/PEC films by solution blending and observed the following; The contact angle values were clearly visible for pure CH film, this can be related with the sorption of water on the surface, and film swelling, followed by water absorption, the water contact angle for CH/ PEC blends 50/50 and 25/75 recorded a higher value (87^○) while for the pure CH, PEC, and CH/PEC 75/25 films were ⁓ 64^○, 75^○, and 74^○ respectively and remained practically constant even after 60 s. The ionic cross-linking effect restricted the CS/PEC blend film swelling and reduced their water sorption.

For the mechanical properties, the tensile strength increased for the CH/PEC blend films. It is evident that the tensile strength of CH/PEC blends presented a large positive deviation from addition law; While pure CH and PEC films showed lower values for the tensile strength 41 and 48 MPa, respectively, while it increased for CH/PEC blend 75/25 was 70 MPa and reached 81 MPa for CH/PEC blends 50/50 and 25/75.

Ionic crosslinking between the chitosan ammonium groups (NH₃⁺) and pectin carboxylate groups (COO−) and thus playing an important role on the physical properties of CH/PEC polyelectrolyte based-films where the electrostatic interactions were responsible for increasing water resistance and mechanical properties of chitosan/pectin films, which allows modulating their thermo-mechanical and other physical properties for specific applications like medicine, agriculture, and food packaging [16].

Younis and Zhao [35] prepared the different films from chitosan (deacetylation degree 67.9%) and high methoxyl apple pectin by casting method. They noted that the tensile strength increased from 1.22 MPa (CH) to 5.06 MPa (CH/PEC), while the elongation at break for the chitosan did not affect by the pectin incorporation; For the water vapor permeability WVP values of the PEC, CH and blend films recorded a significant difference where the WVP value of PEC film (5.53 × 10 g⁻¹² g cm⁻¹·s⁻¹·Pa⁻¹) was much higher than that of PEC/CH film (3.91 × 10 g⁻¹² g cm⁻¹·s⁻¹·Pa⁻¹). Still, the blending does not influence the barrier properties. The more porous structure of PEC film contributes to its higher WVP; the significant reduction in WVP makes the films more suitable for food packaging. Meanwhile, the surface morphology for the films was observed by scanning electron microscopy (SEM), and numerous small pores were evenly distributed in PEC film while big caves were unevenly scattered in CH film; by incorporating the pectin into chitosan, these cavities disappeared, as shown in Figure 1.

Figure 1.

SEM micrographs of the films surface a) pectin, b) chitosan, c) pectin/chitosan films [35].

Chetouani et al. [90] prepared edible films by casting method from apple pectin (DE, 70–75%) and chitosan (viscosity of 800,000 cps) and compared it with chitosan/oxidized pectin by sodium meta periodate (NaIO₄); the results showed the following; The X-ray diffraction, as shown in Figure 2 showed that the chitosan films exhibit broad diffraction peaks observed at (2θ) = 9.8° and 19.9°, which are typical fingerprints of semi-crystalline chitosan. The pure pectin films showed sharp peaks centered at 9.2^○, 12.8^○, 18.5^○, 28.1^○, and 40.1^○ and were considered a semi-crystalline material. After the pectin’s oxidation process, the X-ray diffraction analysis (XRD) is clearly different from that of pure pectin. The peaks at 16.5^○, 24.1^○, 27.5^○, and 33.5^○ indicate less crystalline the oxidized pectin (OPEC).

Figure 2.

X-ray diffractions for the films of pectin (PEC), oxidized pectin (OPEC), and chitosan (CH).

From the above results, the films confirmed that CH’s crystallinity is drastically decreased with the addition of PEC or oxidized PEC. Also, the addition of PEC to CH makes the material amorphous; this could be due to the interacts of chitosan with pectin through inter-molecular hydrogen bonding.

Chetouani et al. [90] noted that the pectin, CH, CH/pectin, and CH/oxidation pectin films do not affect the Gram-negative bacteria (P. aeruginosa, E. coli). In contrast, Gram-positive bacteria (B. subtilis and S. aureus) are more sensitive to the films. Also, there is a strong interaction between chitosan and oxidized pectin films, which influences the thermal decomposition; using these types of films can improve the antibacterial activity of chitosan, which demonstrates them to be promising materials for food packaging and biomedical applications.

Baron et al. [91] reported that the chitosan CH (blue crab waste) and PEC (orange peel) can produce edible films by casting method; they noted that the addition of high concentrations of chitosan with pectin polymer in the films formulations (75:25 ratio) led to producing films with lower solubility and lower moisture content 10.2% and 15.8% respectively, compared with the values of pure pectin; also reduced the water vapor permeability from 1.06 × 10 g⁻¹⁵ g·m⁻¹·s⁻¹·Pa⁻¹ (pectin films) to 0.99 × 10 g⁻¹⁵ g·m⁻¹·s⁻¹·Pa⁻¹ (75 CH:25 PEC), when the quantity of protonated free amino groups (NH₃⁺) in chitosan and the free anionic groups present in the pectin becomes higher in the films, the degree of swelling increased from 14.3% (PEC films) to 15.5% (CH: PEC), while for the mechanical properties, increasing chitosan proportion in biopolymers blend increased the tensile strength (TS) and become more elastic and flexible from 17 MPa (PEC) to 23 MPa (75 CH:25 PEC) also reduced deformability (EB) 37.7–27%, respectively.

4. Conclusion

Today, the food industry’s important challenges are developing environmentally friendly, green, and intelligent food packaging materials to avoid environmental problems caused by synthetic polymer packaging materials. Edible coating of biodegradable materials is considered the most trusted technique for storing fruit and vegetables, an excellent alternative to chemically synthesized preservatives, more effective in prolonging various agricultural products’ shelf life, and inhibiting disease growth on the fruit surface. Biodegradable materials have several characteristics, including biocompatibility, biodegradability, renewability, non-toxicity. Therefore, in recent times the researchers have been focused on edible packaging such as pectin polymers. Pectin is a promising material that can avoid nonbiodegradable polymers problems when applied as an edible coating for different fruits due to its different properties.

Conflict of interest

The authors declare no conflict of interest.