Combination of nisin and ε-polylysine with chitosan coating inhibits the white blush of fresh-cut carrots

Chitosan-metal and metal oxide nanocomposites for active and intelligent food packaging; a comprehensive review of emerging trends and associated challenges

In recent years, significant advancements in biopolymer-based packaging have emerged as a response to the environmental challenges posed by traditional petroleum-based materials. The drive for sustainable, renewable, and degradable alternatives to fossil-based components in the packaging industry has led to an increased focus on chitosan, the second most abundant biopolymer after cellulose. Chitosan offers intrinsic properties such as biodegradability, biocompatibility, antimicrobial activity, excellent barrier and film-forming capabilities, positioning it as an ideal candidate for food packaging applications. However, limitations including inferior mechanical, thermal, barrier properties, and brittleness compared to conventional plastics have limiting its widespread adoption in the food packaging industry. Chitosan has been extensively utilized in various forms, particularly as nanocomposites incorporating metal nanoparticles, leading to chitosan-based nanocomposite films/coatings that synergistically combine the advantageous properties of both chitosan and metal nanoparticles. Through an in-depth analysis of the current research (primarily the last 5 years), this review delves into the physicochemical, mechanical, sensing, and antimicrobial properties of chitosan nanocomposite as an innovative food packaging material. This review will provide insights into the potential toxicity and environmental impact of nanoparticle migration, as well as the prospects and challenges associated with chitosan-metal/metal oxide nanocomposite films in the development of sustainable packaging solutions.

Mechanism of plasma-activated water on the regulation of storage quality of fresh-cut carrots and activation of its antioxidant defence system

This study investigated the impact of plasma-activated water (PAW) on the storage quality of fresh-cut carrots (FCC). The findings revealed that PAW treatment, particularly the 3-min immersion method, led to a substantial enhancement in the quality of the stored carrots. Specifically, the PAW-3 min group decreased by 20.08 %, 55.34 %, and 52.66 % in L*, a*, and b* values respectively (comparing storage days 7 d to 0 d). Notably, the PAW-3 min group demonstrated the least decrease in brightness and exhibited superior yellow color retention compared to the other treatment groups. Concerning weight, a 4.86 % decrease was observed in the PW group from day 0 to day 7 of storage, while the PAW-5 min group exhibited a 2.06 % decrease, suggesting that prolonging the PAW treatment time enhances the retention of sample weight. With regard to hardness, the PAW-3 min group exhibited the least weight loss of 4.62 % among all the treatment groups. The H2O2, a reactive oxygen content, increased from 6.22 ± 0.26 μmol/g to 10.55 ± 0.13 μmol/g with the extension of PAW treatment time, achieving an enzyme inhibition of browning, thus controlling water evaporation and microbial activity. The study demonstrated that PAW ensured uniform water distribution, activated the antioxidant system, and promoted phenolic compound synthesis. It was determined that extended treatment times resulted in cellular damage, and that shorter PAW treatment times (1 to 3 min) were optimal. The findings of this study suggest that this non-chemical method is effective in extending the shelf-life of FCC.

The Effects of Nisin Treatment on the Phenylpropanoid and Physiological Mechanisms of Fresh-Cut Pumpkin

Pumpkin is rich in nutritional value, and it can be eaten as a vegetable or as a staple food, making it popular among modern consumers. However, after fresh cutting, pumpkins are susceptible to moisture loss, softening, microbial contamination, and browning, all of which significantly compromise their quality during storage. Therefore, it is essential to develop effective preservation techniques for maintaining the quality of fresh-cut pumpkins. Nisin, a safe natural preservative, has not yet been studied for use on fresh-cut pumpkins. This study examines the effects of nisin treatment on the quality of fresh-cut pumpkins and then explores preservation mechanisms based on physiological and metabolomic analysis. Results show that 0.4 g/L nisin treatment effectively delays surface browning without impacting odor and maintains microbial safety throughout storage. Additionally, nisin significantly enhances the activities of phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumarate-CoA ligase, and cinnamyl alcohol dehydrogenase, thereby promoting the accumulation of total phenols and carotenoids. The result of the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment of differential metabolites between control and nisin-treated groups reveals that the most significant pathways affected by nisin treatment are amino acid metabolism and phenylpropanoid metabolism, which suggests that nisin enhances preservation by modulating phenylpropanoid metabolism and alleviating amino acid metabolism. This study provides a theoretical basis and offers new insights into improving the storage quality of fresh-cut pumpkins.

Biopolymer-based packaging films/edible coatings functionalized with ε-polylysine: New options for food preservation

In light of the commendable advantages inherent in natural polymers such as biocompatibility, biodegradability, and cost-effectiveness, researchers are actively engaged in the development of biopolymer-based biodegradable food packaging films (BFPF). However, a notable limitation is that most biopolymers lack intrinsic antimicrobial activity, thereby restricting their efficacy in food preservation. To address this challenge, various active substances with antibacterial properties have been explored as additives to BFPF. Among these, ε-polylysine has garnered significant attention in BFPF applications owing to its outstanding antibacterial properties. This study provides a brief overview of the synthesis method and chemical properties of ε-polylysine, and comprehensively examines its impact as an additive on the properties of BFPF derived from diverse biopolymers, including polysaccharides, proteins, aliphatic polyesters, etc. Furthermore, the practical applications of various BFPF functionalized with ε-polylysine in different food preservation scenarios are summarized. The findings underscore that ε-polylysine, functioning as an antibacterial agent, not only directly enhances the antimicrobial activity of BFPF but also serves as a cross-linking agent, interacting with biopolymer molecules to influence the physical and mechanical properties of BFPF, thereby enhancing their efficacy in food preservation.

Exogenous CaCl2 reduces the oxidative cleavage of carotenoids in shredded carrots by targeting CAMTA4-mediated transcriptional repression of carotenoid degradation pathway

Carotenoid oxidative cleavage is a significant factor contributing to the color changes of shredded carrots and treatment with calcium chloride (CaCl2, 1% w/v) has been observed to alleviate the whitening symptom and color loss. However, the specific mechanism by which CaCl2 treatment suppresses carotenoid degradation remains unclear. In this study, the effect of CaCl2 and EGTA (calcium ion chelating agent) treatment on carotenoid biosynthesis and degradation in shredded carrots and the mechanism involved was investigated. CaCl2 treatment promoted the expression and activity of carotenoid biosynthetic enzyme (phytoene synthase, PSY), but inhibited the increases of the degradative enzyme activity of carotenoid cleavage dioxygenase (CCD) and down-regulated the corresponding transcripts, thus delayed the degradation of total carotenoid and maintaining higher levels of major carotenoid compounds including β-carotene, α-carotene, lycopene, and lutein in shredded carrots during storage. However, EGTA treatment promoted the gene expression and enzyme activity of CCD and increased the degradation of carotenoid compounds in shredded carrots during storage. Furthermore, the CaCl2 treatment induced DcCAMTA4, identified as a calcium decoder in shredded carrots, which, in turn, suppressed the expressions of DcCCD1 and DcCCD4 by interacting with their promoters. The transient overexpression of DcCAMTA4 in tobacco leaves led to reduced expression of NtCCD1 and NtCCD4, maintaining a higher content of carotenoids. Thus, CaCl2 alleviated the oxidative cleavage of carotenoids in shredded carrots through the DcCAMTA4-mediated carotenoid degradation pathway.

Inactivation of Desiccation-Resistant Salmonella on Apple Slices Following Treatment with ε-Polylysine, Sodium Bisulfate, or Peracetic Acid and Subsequent Dehydration

Salmonella is capable of surviving dehydration within various foods, such as dried fruit. Dried fruit, including apple slices, have been the subject of product recalls due to contamination with Salmonella. A study was conducted to determine the fate of Salmonella on apple slices, following immersion in three antimicrobial solutions (viz., ε-polylysine [epsilon-polylysine or EP], sodium bisulfate [SBS], or peracetic acid [PAA]), and subsequent hot air dehydration. Gala apples were aseptically cored and sliced into 0.4 cm thick rings, bisected, and inoculated with a five-strain composite of desiccation-resistant Salmonella, to a population of 8.28 log CFU/slice. Slices were then immersed for 2 min in various concentrations of antimicrobial solutions, including EP (0.005, 0.02, 0.05, and 0.1%), SBS (0.05, 0.1, 0.2, and 0.3%), PAA (18 or 42 ppm), or varying concentrations of PAA + EP, and then dehydrated at 60°C for 5 h. Salmonella populations in positive control samples (inoculated apple slices washed in sterile water) declined by 2.64 log after drying. In the present study, the inactivation of Salmonella, following EP and SBS treatments, increased with increasing concentrations, with maximum reductions of 3.87 and 6.20 log (with 0.1 and 0.3% of the two compounds, respectively). Based on preliminary studies, EP concentrations greater than 0.1% did not result in lower populations of Salmonella. Pretreatment washes with either 18 or 42 ppm of PAA inactivated Salmonella populations by 4.62 and 5.63 log, respectively, following desiccation. Combining PAA with up to 0.1% EP induced no greater population reductions of Salmonella than washing with PAA alone. The addition of EP to PAA solutions appeared to destabilize PAA concentrations, reducing its biocidal efficacy. These results may provide antimicrobial predrying treatment alternatives to promote the reduction of Salmonella during commercial or consumer hot air drying of apple slices.

Nisin and ε-polylysine combined treatment enhances quality of fresh-cut jackfruit at refrigerated storage

This study investigated the effects of nisin combined with ε-polylysine on microorganisms and the refrigerated quality of fresh-cut jackfruit. After being treated with distilled water (control), nisin (0.5 g/L), ε-polylysine (0.5 g/L), and the combination of nisin (0.1 g/L) and ε-polylysine (0.4 g/L), microporous modified atmosphere packaging (MMAP) was carried out and stored at 10 ± 1°C for 8 days. The microorganisms and physicochemical indexes were measured every 2 days during storage. The results indicated that combined treatment (0.1 g/L nisin, 0.4 g/L ε-polylysine) had the best preservation on fresh-cut jackfruit. Compared with the control, combined treatment inhibited microbial growth (total bacterial count, mold and yeast), reduced the weight loss rate, respiratory intensity, polyphenol oxidase and peroxidase activities, and maintained higher sugar acid content, firmness, and color. Furthermore, it preserved higher levels of antioxidant compounds, reduced the accumulation of malondialdehyde and hydrogen peroxide, thereby reducing oxidative damage and maintaining high nutritional and sensory qualities. As a safe application of natural preservatives, nisin combined with ε-polylysine treatment has great application potential in the fresh-cut jackfruit industry.

Effect of Combined Chitosan and Hyperbranched Poly-L-Lysine Based Coating on Prolonging the Shelf Life of Oyster Mushroom (Pleurotus ostreatus)

To extend the shelf life of oyster mushroom (Pleurotus ostreatus), the effects of chitosan (CS) and hyperbranched poly-L-lysine (HBPL) combined treatment on quality characteristics, nutritional quality, storage characteristics, and enzyme activity of oyster mushroom during postharvest storage at 4 °C were investigated. The results showed that CS-HBPL combined treatment could significantly reduce rot degree and weight loss and significantly inhibit the browning of oyster mushroom. At the same time, the loss of reducing sugar, vitamin C, soluble protein, and total phenolic was significantly reduced. Compared with the control, CS-HBPL combined treatment could also significantly inhibit an increase in malondialdehyde (MDA) and significantly decrease the relative electrolyte leakage of oyster mushroom. In addition, the activities of catalase (CAT), superoxide dismutase (SOD), phenylalnine ammonialyase (PAL), and peroxidase (POD) were significantly improved, and the activity of polyphenol oxidase (PPO) was significantly inhibited in oyster mushroom. In conclusion, CS-HBPL combined treatment had a good protective effect on the membrane permeability damage of oyster mushroom and could effectively delay the oxidation of phenolic substances and browning of oyster mushroom. Therefore, CS-HBPL combined treatment can be used as a potential strategy to extend the storage time of oyster mushroom.

Synergistic Effects of 1-MCP Fumigation and ε-Poly-L-Lysine Treatments on Delaying Softening and Enhancing Disease Resistance of Flat Peach Fruit

Flat peach, a predominant fruit consumed in China, is highly susceptible to softening and perishable. The impact of 1-methylcycloproene (1-MCP) fumigation combined with ε-poly-L-lysine (ε-PL) on softening and postharvest reactive oxygen species (ROS) and phenylpropanoid pathway metabolisms in peaches and its relationship to disease resistance were investigated. Findings revealed that a combination of 1 µL L-1 1-MCP and 300 mg L-1 ε-PL effectively suppressed the activity of cell-wall-degrading enzymes and the disassembly of cell wall structure, thus maintaining higher firmness and lower decay incidence. Compared to the control group, the synergistic approach bolstered enzymatic responses linked to disease resistance and ROS-scavenge system, consistently preserving total phenolics, flavonoids, ascorbic acid, and glutathione levels. Concurrently, the accumulation of hydrogen peroxide and malondialdehyde was significantly diminished post-treatment. These results show that there is good synergistic effect between 1-MCP and ε-PL, which could effectively maintain the quality of flat peach fruit by modulating cell wall metabolism and enhancing the resistance.

Antimicrobial Compounds in Food Packaging

This review presents current knowledge on antimicrobial agents that are already used in the food packaging industry. At the beginning, innovative ways of food packaging were discussed, including how smart packaging differs from active packaging, and what functions they perform. Next, the focus was on one of the groups of bioactive components that are used in these packaging, namely antimicrobial agents. Among the antimicrobial agents, we selected those that have already been used in packaging and that promise to be used elsewhere, e.g., in the production of antimicrobial biomaterials. Main groups of antimicrobial agents (i.e., metals and metal oxides, organic acids, antimicrobial peptides and bacteriocins, antimicrobial agents of plant origin, enzymes, lactoferrin, chitosan, allyl isothiocyanate, the reuterin system and bacteriophages) that are incorporated or combined with various types of packaging materials to extend the shelf life of food are described. The further development of perspectives and setting of new research directions were also presented.

Antimicrobial Active Packaging Containing Nisin for Preservation of Products of Animal Origin: An Overview

The preservation of food represents one of the greatest challenges in the food industry. Active packaging materials are obtained through the incorporation of antimicrobial and/or antioxidant compounds in order to improve their functionality. Further, these materials are used for food packaging applications for shelf-life extension and fulfilling consumer demands for minimal processed foods with great quality and safety. The incorporation of antimicrobial peptides, such as nisin, has been studied lately, with a great interest applied to the food industry. Antimicrobials can be incorporated in various matrices such as nanofibers, nanoemulsions, nanoliposomes, or nanoparticles, which are further used for packaging. Despite the widespread application of nisin as an antimicrobial by directly incorporating it into various foods, the use of nisin by incorporating it into food packaging materials is researched at a much smaller scale. The researchers in this field are still in full development, being specific to the type of product studied. The purpose of this study was to present recent results obtained as a result of using nisin as an antimicrobial agent in food packaging materials, with a focus on applications on products of animal origin. The findings showed that nisin incorporated in packaging materials led to a significant reduction in the bacterial load (the total viable count or inoculated strains), maintained product attributes (physical, chemical, and sensorial), and prolonged their shelf-life.

Recent advances in polysaccharide-based edible coatings for preservation of fruits and vegetables: A review

Harvested fruits and vegetables are prone to decay and quality deterioration during storage. Although traditional packaging and chemical treatments are effective, they are harmful to the environment and human health. Hence, higher requirements for food preservation technology are increasingly proposed. Nontoxic, renewable, degradable, and edible packaging for fruits and vegetables has become a research hotspot in recent years. Chitosan, alginate, cellulose, pectin, starch, and other polysaccharides as coating materials have been widely used. Compared with traditional plastic packaging and chemical treatment, these coatings exhibited a better preservation effect and higher safety. In this paper, the preservation mechanism of fruits and vegetables by edible coatings treatment was described, and the research on edible coatings used in fruits and vegetables was summarized. The effects polysaccharide-based edible coatings on physicochemical quality and antimicrobial effect of fruits and vegetables were reviewed.

Efficacy of Pectin-Based Coating Added with a Lemon Byproduct Extract on Quality Preservation of Fresh-Cut Carrots

The effect of an edible pectin-based coating supplemented with a lemon byproduct extract on the quality attributes of fresh-cut carrots was studied. Color, hardness, microbial growth, respiratory activity, and antioxidant properties of fresh-cut carrots were studied during 14 days of storage at 4 °C. The application of a pectin-based coating containing a lemon byproduct extract preserved carrots’ physiological parameters, reduced their physiological activity and, thus, delayed senescence. This aspect was also confirmed by the reduced O2 consumption of the coated carrots due to the slowing down of the product’s metabolic reactions. Moreover, coated carrots were characterized by limited changes in colour (ΔE < 3) and white-blush development on both cortical tissue and vascular cylinder, and the presence of calcium chloride in the coating formulation helped to maintain carrots’ hardness throughout storage. In addition, treatment with pectin-based coating and lemon byproduct extract improved microbiological stability of fresh-cut carrots, showing the lowest value of total bacterial count immediately after treatment (2.58 log CFU g−1). This kind of treatment also resulted in a significant preservation of valuable compounds (17.22 mg GAE 100 g−1) and antioxidant activity level (289.49 µM Trolox 100 g−1), reducing the wounding stress induced by processing operations for at least ten days.

Inactivation of Polymicrobial Biofilms of Foodborne Pathogens Using Epsilon Poly-L-Lysin Conjugated Chitosan Nanoparticles

A mixed culture (polymicrobial) biofilm provides a favorable environment for pathogens to persist in the food processing environment and to contaminate food products. Inactivation and eradication of such biofilms from food processing environments are achieved by using harsh disinfectants, but their toxicity and environmentally hostile characteristics are unsustainable. This study aims to use food-grade natural nanoparticulated antimicrobials to control mixed-culture biofilms. Chitosan, a natural broad-spectrum antimicrobial biopolymer (polysaccharide) from crustaceans, was derivatized to produce chitosan nanoparticles (ChNP) as a carrier for another broad-spectrum antimicrobial agent, ε-poly-L-lysine (PL), to synthesize ChNP-PL conjugate. The antimicrobial activity of ChNP and ChNP-PL was tested against mixed-culture biofilms. ChNP-PL (~100 nm) exhibited a synergistic antimicrobial and anti-biofilm effect against mono or mixed-culture biofilms of five foodborne pathogens, including Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica serovar Enteritidis, Escherichia coli O157:H7, and Pseudomonas aeruginosa. ChNP-PL treatment prevented biofilm formation by mono or mixed cultures of L. monocytogenes, P. aeruginosa, and E. coli O157:H7, and bacterial counts were either below the detection limit or caused 3.5-5 log reduction. ChNP-PL also inactivated preformed biofilms. In monoculture biofilm, ChNP-PL treatment reduced L. monocytogenes counts by 4.5 logs, S. Enteritidis by 2 logs, E. coli by 2 logs, and S. aureus by 0.5 logs, while ChNP-PL had no inhibitory effect on P. aeruginosa. In vitro mammalian cell-based cytotoxicity analysis confirmed ChNP-PL to have no deleterious effect on intestinal HCT-8 cell line. In conclusion, our results show ChNP-PL has strong potential to prevent the formation or inactivation of preformed polymicrobial biofilms of foodborne pathogens.

Polyphenolic Antibacterials for Food Preservation: Review, Challenges, and Current Applications

Natural alternatives replacing artificial additives have gained much attention in the consumer’s view because of the growing search for clean label products that are devoid of carcinogenic and toxic effects. Plant polyphenols are considered as suitable alternative natural preservatives with antioxidant and antimicrobial properties. However, their uses in the food industry are undermined by a series of limitations such as low solubility and stability during food processing and storage, lack of standardization, and undesirable organoleptic properties. Different approaches in the use of polyphenols have been proposed in order to overcome the current hurdles related to food preservation. This review article specifically focuses on the antibacterial activity of plant-derived polyphenols as well as their applications as food preservatives, main challenges, and other trends in the food industry.

Advances in the application of chitosan as a sustainable bioactive material in food preservation

Chitosan is obtained from chitin and considered to be one of the most abundant natural polysaccharides. Due to its functional activity, chitosan has received intense and growing interest in terms of applications for food preservation over the last half-century. Compared with earlier studies, recent research has increasingly focused on the exploration of preservation mechanism as well as the targeted inhibition with higher efficiency, which is fueled by availability of more active composite ingredients and integration of more technologies, and gradually perceived as "chitosan-based biofilm preservation." In this Review, we comprehensively summarize the potential antimicrobial mechanisms or hypotheses of chitosan and its widely compounded ingredients, as well as their impacts on endogenous enzymes, oxidation and/or gas barriers. The strategies used for enhancing active function of the film-forming system and subsequent film fabrication processes including direct coating, bioactive packaging film and layer-by-layer assembly are introduced. Finally, future development of chitosan-based bioactive film is also proposed to broaden its application boundaries. Generally, our goal is that this Review is easily accessible and instructive for whose new to the field, as well as hope to advance to the filed forward.

Effects of ε-polylysine and rosemary extract on the quality of large yellow croaker (Pseudosciaena crocea) stored on ice at 4 ± 1°C

To evaluate the quality changes in large yellow croaker (Pseudosciaena crocea) with ε-polylysine and rosemary extract stored on ice at 4 ± 1°C. About 0.1% ε-polylysine (PL) and 0.2% rosemary extract (RE) were individually or in combination with each other were treated with samples. Samples treated with deionized water were regarded as control check (CK) group. Physicochemical (texture profile analysis (TPA), pH, total volatile basis nitrogen (TVB-N), thiobarbituric acid (TBA)), endogenous enzyme activity (cathepsin B and D), proteolytic degradation (Trichloroacetic Acid (TCA)-soluble peptides and Sodium Salt-polyacrylamide gel electrophoresis (SDS-PAGE)), microbiological (Total viable count (TVC), Shewanella bacteria count, Pseudomonas bacteria count, Psychrophilic bacteria count) and sensory evaluation were conducted during the whole storage. As a result, PL + RE could delay the increase in pH, TVB-N, TBA value, and improve the texture attributes compared with the CK group. In addition, PL + RE could inhibit cathepsin B and D activities, protein degradation, and microbial growth effectively. Moreover, the shelf life of samples could be prolonged at least 4 days when compared with the CK group according to the quality index method (QIM) and physicochemical assay, indicating that the PL + RE treatment could maintain the quality of large yellow croaker more effectively. PRACTICAL APPLICATIONS: The preservation of fish is becoming increasingly important in aquatic products. According to the fence theory, a combination of biopreservatives with different functions could be used to maintain the freshness synergistically. Furthermore, this research indicates that the combination of ε-polylysine and rosemary extract, a promising method for the preservation of aquatic products, could slow down the deterioration of large yellow croaker and prolong its shelf life.

Effects of chitosan-based coatings on storage quality of Chinese shrimp

We investigated the effects of chitosan-based coatings on the preservation quality of refrigerated Chinese shrimp for 12 days. Samples of Chinese shrimp were subjected to three different coating treatments, namely chitosan (CH), chitosan and ε-polylysine (CH + ε-PL), chitosan combined with ε-polylysine and carrageenan (CH + ε-PL + CA), and compared with a control. The bacteriological characteristics [total viable count (TVC)], chemical indexes including pH, thiobarbituric acid (TBA) value, K-value, and total volatile basic nitrogen (TVB-N), texture (hardness, chewiness, and elasticity), and sensory changes were assessed. The increases in TVC, pH, TBA, K-value, and TVB-N were observed to be delayed by preservation treatments, and the textural and sensory characteristics indicated that the treated shrimp were preserved more effectively than the control. Treatment with chitosan combined with ε-polylysine and carrageenan was the most effective preservation method than treatment with chitosan alone or chitosan and ε-polylysine; the shelf life was also prolonged. Therefore, treatment with chitosan combined with ε-polylysine and carrageenan is proposed as a potential method for shelf life extension of Chinese shrimp for refrigerated storage.

Effect of carbon dots with chitosan coating on microorganisms and storage quality of modified-atmosphere-packaged fresh-cut cucumber

BACKGROUND

In order to inhibit microorganisms and improve storage quality of fresh-cut cucumber, fresh-cut cucumber was treated by carbon dots (CDs) from kelp/chitosan (CH) coating solution with CD concentrations of 0%, 1.5%, 3% and 4.5% and then packaged as well as stored at 4 °C for 15 days. The effect of CDs/CH coating on microorganisms and the quality of modified-atmosphere-packaged fresh-cut cucumber during storage were investigated.

RESULTS

The CDs was monodispersed spherical morphology with size distribution of 0.54-0.83 nm. Interaction of CDs and CH had the generation of strong hydrogen bond. Inhibition zone diameters of CDs/CH coating against Staphylococcus aureus and Escherichia coli were enhanced with the increase of CD concentrations. Moreover, CDs/CH coating inhibited the growth of total number of colonies, mold, and yeast in modified-atmosphere-packaged fresh-cut cucumber during storage. A coating of 4.5% CDs/CH effectively reduced the losses of weight, firmness, and total soluble solids, the degradation of ascorbic acid content and flavor, and inhibited peroxidases activity, as well as decreased water mobility in fresh-cut cucumber during storage.

CONCLUSION

The results indicated that a CDs/CH coating was helpful for inhibiting microorganisms and improving storage quality, and could be an effective method to prolong shelf life of fresh-cut cucumber. © 2019 Society of Chemical Industry.

The Involvement of the Banana F-Box Protein MaEBF1 in Regulating Chilling-Inhibited Starch Degradation through Interaction with a MaNAC67-Like Protein

Low-temperature storage is a common strategy for preserving and transporting vegetables and fruits. However, many fruits are hypersensitive to chilling injury, including bananas. In the present study, storage conditions of 11 °C delayed the ripening of Fenjiao (Musa ABB Pisang Awak) banana, and the pulp could be softened after ethephon treatment. Storage conditions of 7 °C prevented fruit from fully softening, and fruit contained a significantly higher starch content and lower soluble sugar content. MaEBF1, a critical gene component in the ethylene signaling pathway, was repressed during ripening after fruit had been stored for 12 days at 7 °C. The expression of a series of starch degradation-related genes and a MaNAC67-like gene were also severely repressed. Both MaEBF1 and MaNAC67-like genes were ethylene-inducible and localized in the nucleus. MaNAC67-like protein was able to physically bind to the promoter of genes associated with starch degradation, including MaBAM6, MaSEX4, and MaMEX1. Yeast two-hybrid, GST-pull down, and BiFC assays showed that MaEBF1 interacted with the MaNAC67-like protein, and their interaction further activated the promoters of MaBAM6 and MaSEX4. The current study indicates that MaNAC67-like is a direct regulator of starch degradation and potential for involvement in regulating chilling-inhibited starch degradation by interacting with the ethylene signaling components in banana fruit. The present work paves the way for further functional analysis of MaEBF1 and MaNAC67-like in banana, which will be useful for understanding the regulation of banana starch metabolism and fruit ripening.

Effect of Sodium Trimetaphosphate on Chitosan-Methylcellulose Composite Films: Physicochemical Properties and Food Packaging Application

Environmentally friendly food packaging currently attracts much interest. Sodium trimetaphosphate (STMP) finds specialized applications in food, but it is rarely used as a crosslinking agent. In this study, STMP was used as a crosslinking agent to prepare chitosan/methylcellulose composite films. Both antibacterial and physicochemical properties of the composite film were improved by crosslinking with STMP. The crosslinked films, with good antibacterial activity (~99%), had increased tensile strength, a higher elongation at break, a lower swelling ratio and solubility, and a lower enzymatic degradation than the non-crosslinked films. Furthermore, the crosslinked films showed an excellent preservative effect on fresh-cut wax gourd after three days at room temperature. The obtained films crosslinked by STMP can be potentially applied to the food industry, such as food functional packaging, providing a novel alternative to traditional plastic packages.

Effect of Carnauba Wax-Based Coating Containing Glycerol Monolaurate on Decay and Quality of Sweet Potato Roots during Storage

Because of high water loss and rot observed in postharvest sweet potato ( Ipomoea batatas (L.) Lam.) roots, a carnauba wax (CW)-based nanoemulsion without or with glycerol monolaurate (CW-GML) was developed by a high-energy emulsification approach. The effects of the two coatings on decay, respiration rate, weight loss, surface color, total soluble sugar, and starch content as well as the sensory quality of sweet potato roots were investigated during storage at 20°C for 50 days. Compared with the control treatment (water) and CW coating alone, CW-GML coating exhibited higher emulsion stability and antifungal activity, and treatment resulted in a uniform and continuous coating on roots. The CW-GML and CW coatings both effectively reduced root weight loss and respiration rate and inhibited decay incidence compared with control roots during storage. The CW-GML coating showed markedly stronger inhibition of root rot than the CW coating. Both the CW-GML and CW coatings promoted an increase in root sweetness but did not negatively impact perceived flavor. The overall results demonstrate that the CW-GML coating holds great promise as an effective postharvest technology to preserve food quality and extend shelf life of sweet potato roots.

Development of antibacterial ε-polylysine/chitosan hybrid films and the effect on citrus

In this study, the ε-polylysine (PL)/chitosan (CS) composite films with the PL concentration of 0%, 1%, 3%, 5% and 7% were prepared via casting method. The Fourier transform infrared (FTIR), scanning electron microscope (SEM), mechanical and antibacterial properties of PL/CS composite films, as well as the effect of PL/CS coatings on citrus were observed. FTIR spectra suggested that there was no strong hydrogen bond between CS and PL. SEM images indicated that the film surface was smooth and the addition of PL to chitosan lead to more holes. The tensile strength was deceasing and the elongation at break of the films was elevating with the increase of PL content. The antibacterial activity against Staphylococcus aureus and Escherichia coli of PL/CS composite films was enhanced with increasing of PL content. Furthermore, it was found that the PL/CS coatings inhibited efficiently the decline of total soluble solids (TSS), ascorbic acid content and reduced the disease incidence of citrus, compared with the control. Also the disease incidence of citrus was decreasing with the increase of PL content. However, the weight loss did not show significant differences between the coated citrus and control during the whole storage period.

Emerging Chitosan-Based Films for Food Packaging Applications

Recent years have witnessed great developments in biobased polymer packaging films for the serious environmental problems caused by the petroleum-based nonbiodegradable packaging materials. Chitosan is one of the most abundant biopolymers after cellulose. Chitosan-based materials have been widely applied in various fields for their biological and physical properties of biocompatibility, biodegradability, antimicrobial ability, and easy film forming ability. Different chitosan-based films have been fabricated and applied in the field of food packaging. Most of the review papers related to chitosan-based films are focusing on antibacterial food packaging films. Along with the advances in the nanotechnology and polymer science, numerous strategies, for instance direct casting, coating, dipping, layer-by-layer assembly, and extrusion, have been employed to prepare chitosan-based films with multiple functionalities. The emerging food packaging applications of chitosan-based films as antibacterial films, barrier films, and sensing films have achieved great developments. This article comprehensively reviews recent advances in the preparation and application of engineered chitosan-based films in food packaging fields.

The Effects of Using Sodium Alginate Hydrosols Treated with Direct Electric Current as Coatings for Sausages

We investigated the effect of sodium alginate hydrosols (1%) with 0.2% of NaCl treated with direct electric current (DC) used as a coating on microbial (Total Viable Counts, Psychrotrophic bacteria, yeast and molds, Lactic acid bacteria, Enterobacteriaceae), physiochemical (pH, lipid oxidation, antioxidant activity, weight loss, color) and sensory properties of skinned pork sausages or with artificial casing stored at 4 °C for 28 days. Moreover, the cytotoxicity analysis of sodium alginate hydrogels was performed. The results have shown that application of experimental coatings on the sausage surface resulted in reducing all tested groups of microorganisms compared to control after a 4-week storage. The cytotoxicity analysis revealed that proliferation of RAW 264.7 and L929 is not inhibited by the samples treated with 200 mA. Ferric reducing antioxidant power (FRAP) and free radical scavenging activity (DPPH) analyses showed that there are no significant differences in antioxidant properties between control samples and those covered with sodium alginate. After 28 days of storage, the highest value of thiobarbituric acid-reactive substances (TBARS) was noticed for variants treated with 400 mA (1.07 mg malondialdehyde/kg), while it was only slightly lower for the control sample (0.95 mg MDA/kg). The obtained results suggest that sodium alginate treated with DC may be used as a coating for food preservation because of its antimicrobial activity and lack of undesirable impact on the quality factors of sausages.

Incorporated α-amylase and starch in an edible chitosan–procyanidin complex film increased the release amount of procyanidins

The α-amylase was embedded in edible chitosan–procyanidins film, and the release of procyanidins was by starch hydrolysis.