Antioxidant packaging films developed based on chitosan grafted with different catechins: Characterization and application in retarding corn oil oxidation

High-adhesion antimicrobial composite coating incorporating quaternary chitosan and tea tree oil for enhanced preservation of fruits and vegetables

This study developed high-adhesion quaternary chitosan coatings using amphiphilic HACC-oleic acid conjugates (HACC-OA) to enhance fruit and vegetable preservation. HACC-OA demonstrated improved viscosity and adhesion, providing a stable carrier for tea tree oil (TTO). The resulting TTO@HACC-OA coatings exhibited significantly reduced contact angle (43.7°) and increased retention amount on strawberry surfaces. Furthermore, TTO@HACC-OA demonstrated a lower volatilization rate of TTO (27.8 %) compared to pure TTO (49.5 %) and an enhanced synergistic antimicrobial activity (EC50 = 1.51 mg/mL) against Botrytis cinerea Pers compared to HACC alone (EC50 = 1.58 mg/mL). Preservation experiments revealed that TTO@HACC-OA effectively maintained color and firmness, reduced decay index and weight loss, delayed decline in vitamin C content of strawberries, postponed increase in total phenolic content, and mitigated malondialdehyde accumulation. Therefore, the prepared TTO@HACC-OA composite coating with excellent adhesion ability and preservation effect holds great potential for applications in fruit and vegetable preservation.

Preparation and characterization of Levan composite film incorporating vanillin for use as a potential edible coating for peony seed oil

The study prepared an edible packaging material for peony seed oil by adding natural antioxidant vanillin to a microbial Levan composite film. The presence of highly branched Levan, containing polyhydroxyl groups, significantly enhanced the maximum tension (26.57 N), tensile strength (36.31 MPa), and elongation at break (42.15 %) of the Aga/Lev film. The values were 9.84-fold, 5.74-fold, and 1.11-fold higher than those of Aga films, respectively. Furthermore, SEM and FTIR analysis revealed that Levan increased the intermolecular force of the vanillin composite film (Aga/Lev/Gly/Van), forming a dense gel network with a Schiff base reaction occurring between vanillin and glycine. The addition of vanillin and glycine slightly lowered the transparency of the film but enhanced the ultra violet (UV)-blocking with 100 % UV-region and 91 % visible region light screening. The Aga/Lev/Gly/Van films showed strong antioxidant efficacy with 91.85 % ABTS and 44.33 % DPPH radical scavenging potential. The electrical conductivity, P-anisidine value, thiobarbituric acid value, and fatty acid distribution of peony seed oil samples were analyzed after accelerated storage. The Aga/Lev/Gly/Van group had a significantly higher retention rate (95.65 %) for total conjugated fatty acids compared to the control group (84.17 %). The utilization of Aga/Lev/Gly/Van film packaging effectively extended the shelf life of peony seed oil and retarded the degradation of unsaturated fatty acids in the oil. Therefore, Levan composite films incorporating vanillin can be used as sustainable packaging materials to minimize the oxidation of susceptible foods.

Polysaccharide-Based Packaging Coatings and Films with Phenolic Compounds in Preservation of Fruits and Vegetables-A Review

Considerable interest has emerged in developing biodegradable food packaging materials derived from polysaccharides. Phenolic compounds serve as natural bioactive substances with a range of functional properties. Various phenolic compounds have been incorporated into polysaccharide-based films and coatings for food packaging, thereby enhancing product shelf life by mitigating quality degradation due to oxidation and microbial growth. This review offers a comprehensive overview of the current state of polysaccharide-based active films and coatings enriched with phenolic compounds for preserving fruits and vegetables. The different approaches for the addition of phenols to polysaccharides-based packaging materials are discussed. The modifications in film properties resulting from incorporating polyphenols are systematically characterized. Then, the application of these composite materials as protectants and intelligent packaging in fruit and vegetables preservation is highlighted. In future, several points, such as the preservative mechanism, safety evaluation, and combination with other techniques along the whole supply chain could be considered to design polyphenol-polysaccharides packaging more in line with actual production needs.

Preparation and characterization of polyphenol-chitosan conjugate-eugenol essential oil microcapsule and its effect on storage behavior of cherry tomato

Given the high volatility, low water solubility, and oxidative sensitivity of essential oils, this study synthesized microcapsules of essential oil (EEO) (quercetin-chitosan-EEO [QE-CS-EEO]) using a QE-CS graft copolymer as the wall material and EEO as the core material. Research findings indicate that QE-CS exhibits superior in vitro antioxidant activity, with scavenging abilities for 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) ABTS+ radicals being 58.71% and 77.03% greater than those of CS, respectively, thereby providing more effective protection for the essential oil. In comparison to CS essential oil, microcapsules (CS-EEO), QE-CS-EEO demonstrated an 18.65% increase in EEO encapsulation efficiency, achieving a total encapsulation efficiency of 41.29%. Based on these results, various edible coating solutions were formulated, including Control, E1 (1% CS), E2 (0.5% CS + 0.5% CS-EEO), E3 (0.5% CS + 0.5% QE-CS-EEO), and E4 (1% EEO), to extend the shelf life of cherry tomatoes. Notably, cherry tomatoes treated with the E3 formulation maintained superior freshness indicators, exhibiting an extended shelf life of approximately 9-12 days compared to the control group. This study aims to explore a novel microcapsule wall material and provide a strategy for extending the shelf life of fruits and vegetables, thereby minimizing food waste.

In situ modification of foaming bacterial cellulose with chitosan and its application to active food packaging

Owing to a lack of specific biological functions, bacterial cellulose (BC) has been restricted in its application to the field of active packaging. In this study, we developed antimicrobial packaging materials using foaming BC (FBC) with chitosan (CS) and applied it to the preservation of chilled sea bass. The material property analysis demonstrated that 1.5 % CS/FBC maintained a high water content of 91 %, a swelling ratio of 75.6 %, great stress of 1.61 MPa, and great strain of 1.87 %. CS incorporation into FBC also decreased its crystallinity from 73.39 % to 69.3 %. Meanwhile, 1.5 % CS/FBC also provided great antimicrobial ability against Escherichia coli and Staphylococcus aureus by approximately 2 log colony-forming units/mL inhibition utilizing contact-killing. Results of the preservation assessment indicated that 1.5 % CS/FBC efficiently inhibited Shewanella putrefaciens growth, reduced total volatile basic nitrogen release, and slightly inhibited lipid oxidation. Based on the above results, CS/FBC is an ecofriendly biomaterial produced from a microorganism that possesses high absorbency and strong antibacterial properties, making it suitable for development as antibacterial active packaging.

Water-soluble chlorogenic acid-chitosan and polydatin-chitosan conjugates: antibacterial activity and inhibition of lipid and protein oxidation

BACKGROUND

Chitosan (CS), an abundant alkaline polysaccharide, is valued for its biocompatibility, non-toxicity, and antibacterial properties. However, its limited solubility and modest antioxidant activity constrain its utility. Grafting polyphenols onto chitosan through the use of grafting reactions can enhance both the solubility and bioactivity of chitosan. Among the techniques employed, the free radical grafting method is favored for its simplicity, environmental sustainability, and its effectiveness in preserving biological activity.

RESULTS

In this study, chlorogenic acid (CGA) and polydatin (PLD) were conjugated successfully to chitosan by a Vc/H2O2 redox system. Analytical techniques such as ultraviolet-visible (UV-visible) spectroscopy, fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR) were employed to confirm the formation of covalent bonding between the polyphenol molecules and the chitosan backbone. The novel conjugates displayed superior antioxidant properties in comparison with pristine chitosan, as evidenced by their enhanced 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, and hydroxyl radical scavenging capacities, and Fe2+ reducing power. Both CGA-CS and PLA-CS exhibited excellent lipid and protein oxidation inhibition capabilities. Furthermore, the conjugates were shown to have significant antibacterial effects against four common pathogenic bacteria: Pseudomonas fluorescens, Pseudomonas aeruginosa, Pseudomonas putida, and Staphylococcus aureus (P < 0.05).

CONCLUSION

The newly synthesized water-soluble polyphenol-chitosan conjugates demonstrated remarkable biological activity, particularly CGA-CS. This study offers new insights and a strong theoretical foundation for developing natural food preservation materials with potential applications in the food industry. © 2024 Society of Chemical Industry.

Characterization of free radical-mediated Pleurotus ostreatus polysaccharide-EGCG conjugates for chilled minced pork preservation

To improve the functions of Pleurotus ostreatus polysaccharide (POP), POP-EGCG conjugates were prepared using free radical graft polymerization reactions and were characterized using UV-vis, FT-IR, SEM, XRD, DSC, TG, particle size and potential, three-phase contact angle, and rheological tests; The antioxidant and antibacterial ability in vitro were detected. Moreover, effects of POP-EGCG on the quality of refrigerated minced pork were investigated. The results showed the optimal preparation conditions of POP-EGCG were 1 % POP, 1.3 % EGCG, 0.25 % Vc, 16 % concentration of H2O2, and reaction 17 h. The POP-EGCG showed the characteristic peak of EGCG and was a mesh honeycomb with rough and porous surface; It had higher crystallinity, increased particle size, but decreased thermal stability, solubility, and viscosity, and significantly enhanced antioxidant and antibacterial ability. The POP-EGCG effectively improved the sensory quality and inhibited lipid oxidation of chilled minced pork, and extended the shelf life of minced pork up to 9 days at 4 °C. Specifically, the TVB-N and TBARS of minced pork in the POP-EGCG group were respectively 14.93 mg/100 g and 0.9 mg MDA/kg, which were lower than the spoilage thresholds in the national standard. This study provides a theoretical basis for further development of natural antioxidants and antimicrobial agents.

Screening and Characterization of Antioxidant Film Applicable to Walnut Kernels from Juglans sigillata

Walnuts play a positive role in human health due to their large amounts of unsaturated fatty acids, whereas lipid oxidation can easily occur during storage. Herein, three natural antioxidants (epicatechin, sesamol, and myricetin) were added to the composite film cross-linked with chitosan and soy protein peptide, and the antioxidant film appropriate for the preservation of walnut kernels from Juglans sigillata was screened to improve the storage quality of walnuts. The results showed that three antioxidant films could all enhance the storage performance of walnut kernels, with sesamol being the best. The characterization of antioxidant film cross-linked with chitosan and soy protein peptide containing sesamol (C/S-ses film) revealed that the composite film improved the slow release and stability of sesamol; in addition, the presence of sesamol could effectively reduce the light transmittance and water vapor permeability of the composite film, together with significantly enhancing the antioxidant and antimicrobial activities, resulting in an effective prolongation of the storage period of walnut kernels. These findings indicated that C/S-ses possess excellent potential for retarding the oxidative rancidity of unsaturated fatty acids and will provide an effective strategy for the preservation of walnut kernels.

Preparation, Characterization and Application of Active Food Packaging Films Based on Sodium Alginate and Twelve Varieties of Mandarin Peel Powder

The industrial processing of mandarin fruits yields a large amount of peel waste, resulting in economic losses and environmental pollution. The peels of mandarin fruits are a good source of biomass and active substances that can be used to produce food packaging systems. In this study, active food packaging films were prepared based on sodium alginate and twelve varieties of mandarin peel powder. The structures, properties, and corn oil packaging performance of the films were compared. Results showed that the twelve varieties of mandarin peel powder differed in pectin, lipid, protein, crude fiber, and total phenol contents. The prepared films all exhibited a yellow color, 117.73-152.45 μm thickness, 16.39-23.62% moisture content, 26.03-90.75° water contact angle, 5.38-8.31 × 10-11 g m-1 s-1 Pa-1 water vapor permeability, 5.26-12.91 × 10-20 m2 s-1 Pa-1 oxygen permeability, 4.87-7.90 MPa tensile strength, and 13.37-24.62% elongation at break. Notably, the films containing mandarin peel powder with high pectin and lipid contents showed high moisture/oxygen barrier ability and mechanical properties. The films containing mandarin peel powder with high total phenol content exhibited high antioxidant- and antimicrobial-releasing abilities and good performance in delaying corn oil oxidation. Overall, the results suggested that the films have good application potential in active food packaging.

Preparation, characterization and application of antioxidant packaging films based on chitosan-epicatechin gallate conjugates with different substitution degrees

In this study, chitosan (CS) was conjugated with epicatechin gallate (ECG) to prepare CS-ECG conjugates with different substitution degrees (5.18 %, 6.36 % and 7.74 %). Then, antioxidant packaging films were fabricated by blending CS and CS-ECG conjugates. The impact of CS-ECG conjugates' substitution degree on the functionality of CS/CS-ECG films was determined. CS-ECG conjugates showed UV absorption at 275 nm, proton signal at 6.85 ppm and infrared absorption at 1533 cm-1, assigning to the conjugated ECG. As compared with CS, CS-ECG conjugates exhibited less crystalline state but higher antioxidant activity. The structural characterization of CS/CS-ECG films showed CS and CS-ECG conjugates formed hydrogen bonds. CS/CS-ECG films displayed 26.35 %-29.23 % water solubility, 85.61°-86.96° water contact angle, 3.11-3.41 × 10-11 g m-1 s-1 Pa-1 water vapor permeability, 0.29-0.34 cm3 mm m-2 day-1 atm-1 oxygen permeability, 31.54-36.20 MPa tensile strength, 50.12 %-56.40 % elongation at break, as well as potent antioxidant activity and oil oxidation inhibitory ability. Notably, the film containing CS-ECG conjugate with 7.74 % substitution degree had the strongest barrier ability, mechanical property, antioxidant activity and oil oxidation inhibitory ability. Results suggested the substitution degree of CS-ECG conjugates was positively correlated with the barrier, mechanical and antioxidant properties of CS/CS-ECG films.

Multicomponent chitosan complex/polyvinyl alcohol blended film with full-band UV-shielding performance and excellent antioxidant property for active food packaging

Utilizing renewable natural resources to construct multifunctional packaging materials is critical to achieving sustainable development in the food packaging industry. In this study, we crafted transparent films with comprehensive UV-shielding and antioxidant properties by blending a multicomponent chitosan complex with polyvinyl alcohol (PVA), subsequently applied to preserve peanut butter. The multicomponent chitosan complex, synthesized from chitosan, ferulic acid (FA), and 5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-7-carboxylic acid (TPCA) through direct heating in water, served as the foundation. This chitosan complex was seamlessly blended with PVA, resulting in the creation of a transparent film through the solvent casting method. A meticulous investigation into the chemical structure and physicochemical properties of the blended films was conducted. The FA and TPCA components exhibited robust ultraviolet absorption properties, conferring virtually complete full-band ultraviolet shielding ability to the blend film. Additionally, FA endowed the blended film with significant antioxidant activity. The effectiveness of the chitosan complex/PVA blended film in preserving peanut butter from oxidative spoilage was demonstrated, showcasing its robustness in food preservation. Our research underscores the significance of creating advanced packaging materials from sustainable sources.

Effect of tea polyphenols on chitosan packaging for food preservation: Physicochemical properties, bioactivity, and nutrition

Chitosan packaging has been widely studied for food preservation, the application of which is expanded by the incorporation of tea polyphenols. This paper reviews the influence of tea polyphenols incorporation on chitosan-based packaging from the perspectives of physicochemical properties, bioactivity used for food preservation, and nutritional value. The physicochemical properties included optical properties, mechanical properties, water solubility, moisture content, and water vapor barrier property, concluding that the addition of tea polyphenols improved the opacity, water solubility, and water vapor barrier property of chitosan packaging, and the mechanical properties and water content were decreased. The bioactivity used for food preservation, that is antioxidant and antimicrobial properties, is enhanced by tea polyphenols, improving the preservation of food like meat, fruits, and vegetables. In the future, efforts will be needed to improve the mechanical properties of composite film and adjust the formula of tea polyphenols/chitosan composite film to apply to different foods. Besides, the identification and development of high nutritional value tea polyphenol/chitosan composite film is a valuable but challenging task. This review is expected to scientifically guide the application of tea polyphenols in chitosan packaging.

Chitosan-grafted phenolic acids as an efficient biopolymer for food packaging films/coatings

Chitosan (CS), a bio-renewable natural material, has the potential to be utilized as a biopolymer for food packaging films (PFs)/coatings. However, its low solubility in dilute acid solutions and poor antioxidant and antimicrobial activities limit its application in PFs/coatings. To address these restrictions, chemical modification of CS has garnered increasing interest, with graft copolymerization being the most extensively used method. Phenolic acids (PAs) as natural small molecules are used as excellent candidates for CS grafting. This work focuses on the progress of CS grafted PA (CS-g-PA) based films, introducing the chemistry and methods of preparing CS-g-PA, particularly the effects of different PAs grafting on the properties of CS films. In addition, this work discusses the application of different CS-g-PA functionalized PFs/coatings for food preservation. It is concluded that the food preservation capability of CS-based films/coatings can be improved by modifying the properties of CS-based films through PA grafting.

Antibacterial and antioxidant properties of phenolic acid grafted chitosan and its application in food preservation: A review

Chitosan is a bio-renewable natural polymeric material. The antibacterial and antioxidant activity of chitosan can be enhanced by grafting with phenolic acids to further expand its application in food. Therefore, this paper focuses on reviewing the structure, antimicrobial and antioxidant activities and their mechanisms with phenolic acid-g-CS, evaluating its cytotoxicity, and describing its application in various food preservation. In general, different reaction mechanisms of phenolic acid-g-CS synthesis lead to different product structures. Compared to chitosan, phenolic acid-g-chitosan exhibited enhanced antibacterial and antioxidant activities. The toxicity assessment showed that phenolic acid-g-CS is not cytotoxic. Moreover, phenolic acid-g-CS has been applied to a variety of food products such as fruits, vegetables and meat with good results. Overall, this review provides a certain reference for subsequent researchers to design phenolic acid-g-CS more rationally and for the subsequent development of phenolic acid-g-CS in food preservation.

The Loading of Epigallocatechin Gallate on Bovine Serum Albumin and Pullulan-Based Nanoparticles as Effective Antioxidant

Due to its poor stability and rapid metabolism, the biological activity and absorption of epigallocatechin gallate (EGCG) is limited. In this work, EGCG-loaded bovine serum albumin (BSA)/pullulan (PUL) nanoparticles (BPENs) were successfully fabricated via self-assembly. This assembly was driven by hydrogen bonding, which provided the desired EGCG loading efficiency, high stability, and a strong antioxidant capacity. The encapsulation efficiency of the BPENs was above 99.0%. BPENs have high antioxidant activity in vitro, and, in this study, their antioxidant capacity increased with an increase in the EGCG concentration. The in vitro release assays showed that the BPENs were released continuously over 6 h. The Fourier transform infrared spectra (FTIR) analysis indicated the presence of hydrogen bonding, hydrophobic interactions, and electrostatic interactions, which were the driving forces for the formation of the EGCG carrier nanoparticles. Furthermore, the transmission electron microscope (TEM) images demonstrated that the BSA/PUL-based nanoparticles (BPNs) and BPENs both exhibited regular spherical particles. In conclusion, BPENs are good delivery carriers for enhancing the stability and antioxidant activity of EGCG.

Non-radical synthesis of amide chitosan with p-coumaric acid and caffeic acid and its application in pork preservation

p-Coumaric acid and caffeic acid were grafted onto chitosan through a non-radical synthesis method to improve the properties of chitosan and expand its application in food industry. Structural characterization demonstrated that the -COOH of the two phenolic acids were bonded to the -NH₂ of the chitosan and formed an acylamino. The grafting ratios of p-coumaric acid-modified chitosan (Cm-CTS) and caffeic acid-modified chitosan (Cf-CTS) reached 10.30 % and 9.78 %, respectively. After modification, the water solubility of the chitosan greatly improved from 9.33 % (native chitosan, Nt-CTS) to 77.33 % (Cm-CTS) and 100 % (Cf-CTS). Besides, the involvement of phenolic acid and caffeic acid endowed the chitosan with strengthened antioxidation and antibacterial activities against Escherichia coli and Staphylococcus aureus. Nt-CTS and the modified chitosans were coated on the pork surface. The results indicated that Nt-CTS effectively inhibited pork spoilage and the modified chitosans could further prolong the shelf life of pork.

Antioxidant packaging films developed by in-situ cross-linking chitosan with dialdehyde starch-catechin conjugates

In this study, four dialdehyde starch-catechin (DAS-catechin) conjugates were prepared by conjugating (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG) with dialdehyde starch. Then, DAS-catechin conjugates were used as antioxidant and cross-linking agents to produce chitosan (CS) based antioxidant packaging films. The functionality of CS/DAS-catechin conjugate films was determined. Results showed four DAS-catechin conjugates formed Schiff-base linkages and hydrogen bond interactions with CS, resulting in improved film uniformity. Compared with plain CS film, CS/DAS-catechin conjugate films owned higher UV-vis light, water vapor and oxygen barrier ability, lower swelling degree, and stronger tensile strength, thermal stability and antioxidant activity. The cross-linking between CS and DAS-catechin conjugates delayed the biodegradable process of CS film. CS/DAS-catechin conjugate films showed good performance on inhibiting sunflower seed oil oxidation. Notably, CS/DAS-ECG conjugate film had the highest oxygen barrier, mechanical and antioxidant performances among four CS/DAS-catechin conjugate films. Therefore, CS/DAS-ECG conjugate film is an antioxidant packaging candidate for edible oil.