Effect of chitosan coatings enriched with cinnamon oil on the quality of refrigerated rainbow trout

Enhancing safety and quality of shrimp by nanoparticles of sodium alginate-based edible coating containing grapefruit seed extract

Edible coatings are safe and effective in extending the shelf life of foods. In this study, a nanoparticle-based edible coating solution was prepared, containing alginate as a coating agent and grapefruit seed extract as an antibacterial agent to improve the safety and quality of shrimp during storage. Shrimp coated with this formulation were maintained at 4°C for 8 days, and periodically analyzed for changes in sensory, chemical [total volatile basic nitrogen (TVB-N) and pH] and microbial parameters. The uncoated shrimp exceeded the microbiological limits at 7.87 log CFU/g on Day 4 of storage, whereas the nanoparticle-based coated shrimp did not exceed the limit by Day 8 of storage. In addition, uncoated shrimp tended to maintain their quality, while uncoated shrimp deteriorated due to increased TVB-N values, pH values, and off-flavors. Nanoparticles are easily dispersed in food to minimize flavor impact and enhance diffusion and bioactivity. We concluded that the nanoparticles coating extended the shelf life of shrimp by more than 5 days. Therefore, the use of nanoparticle-based coatings could be a new and effective way to maintain shrimp quality.

Antibacterial effects of extracted corn zein with garlic extract-based nanoemulsion on the shelf life of Vannamei prawn (Litopenaeus vannamei) at refrigerated temperature

BACKGROUND

Litopenaeus vannamei is one of the most perishable foods due to microorganism growth. Using essential oil-based nanoemulsion as a biodegradable and edible coating can enhance the shelf life of shrimp at refrigerated temperature through retarding microbial growth compared to synthetic coatings.

METHODS

Zein was extracted from 50 g dry milled corn with ethanol. Garlic essential oil was prepared by mixing with Tween 80. Nanoemulsion was prepared in an ultrasonic bath. DLS analysis, turbidity, and stability of nanoemulsions were performed. Radical scavenging activity, and total phenol content were done for evaluation of garlic essential oil and nanoemulsion. A 10% zein solution was prepared using ethanol 95% and glycerol plasticizer (2.5%). In the end, various microbial analysis, peroxide value, the thiobarbituric acid reactive substance (TBARS) value, the total volatile basic nitrogen (TVB-N) values, and sensory evaluations of different shrimp samples were determined.

RESULTS

Corn zein along with garlic-based nanoemulsion, had a great impact on the TVB-N, TBARS, and peroxide value (which indicated that z+24% garlic nanoemulsion group was the lowest among other groups on days 3, 7, and 14 (p < 0.05) as well as microbial properties (garlic EO nanoemulsion had significantly better antibacterial effectiveness compared to other groups (p < 0.05)), and sensory evaluation (the z+24% garlic nanoemulsion sample received a significantly higher score than other groups (p < 0.05)) of Litopenaeus vannamei.

CONCLUSIONS

Corn zein nanoemulsion functioned as an antioxidant and antimicrobial agent, increasing the shelf life of Litopenaeus vannamei at refrigerated temperature.

PRACTICAL APPLICATION

Emerging nanotechnology-based approaches with no side-effects on immune system of consumers plays a vital role in bioactive packaging, and on reduction of food spoilage or food poisoning in the transportation, exporting, and distribution stages of food products, especially marine-based products with cold chain transportation. Additionally, it can reduce aquaculture and environmental risks due to the usage of chemical agents used in packaging. Our results showed that administration of a corn zein with nanoemulsion of garlic extract can prolong shelf life of Litopenaeus vannamei. The paper should be of interest to readers such as food microbiologists, aquaculture scientists, fisheries scientists, marine biologists, biomaterial scientists, food packaging industrialists, medical microbiologists, public health managers, and health system managers.

Effect of Plasma-Activated Water on Shewanella putrefaciens Population Growth and Quality of Yellow River Carp (Cyprinus carpio) Fillets

ABSTRACT

Plasma-activated water (PAW) is a new sanitizer that has received considerable attention for application in food industries. This research aimed to evaluate the effect of PAW on the inactivation of Shewanella putrefaciens and quality attributes of Yellow River carp (Cyprinus carpio) fillets. The carp fillet samples were immersed in sterile deionized water (SDW) or SDW activated by plasma discharge for 120 s (PAW120) for 1.5, 3.0, 4.5, or 6.0 min. After being treated by PAW120 for 6 min, the population of S. putrefaciens on carp fillets was significantly (P < 0.05) decreased by 1.03 log CFU/g. Compared with SDW-treated samples, the L* value of PAW120-treated carp fillets was increased and the a* value was decreased after PAW120 treatment, whereas there was no significant (P > 0.05) difference in the b* value. Compared with SDW, PAW120 caused no significant (P > 0.05) changes in sensory properties and texture attributes of carp fillets including hardness, springiness, gumminess, and cohesiveness. However, 6-min PAW120 treatment caused a significant increase in the lipid oxidation level and a decrease in the pH value of the carp fillets. This work provides a basis for the potential application of PAW in the preservation of aquatic products.

HIGHLIGHTS

Effects of Peppermint Extract and Chitosan-Based Edible Coating on Storage Quality of Common Carp (Cyprinus carpio) Fillets

Edible coatings have recently been developed and applied to different food matrices, due to their numerous benefits, such as increasing the shelf life of foods, improving their appearance, being vehicles of different compounds, such as extracts or oils of various spices that have antioxidant and antimicrobial activity, as well as being friendly to the environment. The objective of this research was to develop a new edible coating based on chitosan enriched with peppermint extract and to evaluate its effectiveness to inhibit microbial development in vitro and improve both the quality and shelf life of common carp (Cyprinus carpio) during refrigerated storage (4 ± 1 °C). Three treatments were used: edible coating (C + EC), edible coating +, 5% chitosan (C + ECCh) and edible coating + 1.5% chitosan + 10% peppermint (C + ECChP). Prior the coating carp fillets; the antibacterial activity and antioxidant capacity were evaluated in the peppermint extract and coating solutions. After coating and during storage, the following were determined on the fillet samples: microbiological properties, observed for ECP, an inhibition halo of 14.3 mm for Staphylococcus aureus, not being the case for Gram-negative species, for ECCh, inhibition halos of 17.6 mm, 17.1 mm and 16.5 mm for S. aureus, Salmonella typhimurium and Escherichia coli, respectively; for the ECChP, inhibition halos for S. aureus, S. typhimurium and E. coli of 20 mm, 17 mm and 16.8 mm, respectively. For the physicochemical characteristics: an increase in solubility was observed for all treatments during storage, reaching 46.7 mg SN protein/mg total protein for the control, and values below 29.1 mg SN protein/mg total protein (p < 0.05), for fillets with EC (C + EC > C + ECCh > C + ECChP, respectively at the end of storage. For the pH, maximum values were obtained for the control of 6.4, while for the fillets with EC a maximum of 5.8. For TVB-N, the fillets with different CE treatments obtained values (p < 0.05) of 33.3; 27.2; 25.3 and 23.3 mg N/100 g (control > C + E C > C + ECCh > C + ECChP respectively). Total phenolic compounds in the aqueous peppermint extract were 505.55 mg GAE/100 g dried leaves, with 98.78% antioxidant capacity in the aqueous extract and 81.88% in the EC. Biomolecule oxidation (hydroperoxide content) had a significant increase (p < 0.05) in all treatments during storage, 1.7 mM CHP/mg protein in the control, to 1.4 in C + EC, 1.27 in C + ECCh and 1.16 in C + ECChP; TBARS assay values increased in the different treatments during refrigerated storage, with final values of 33.44, 31.88, 29.40 and 29.21 mM MDA/mg protein in the control; C + EC; C + ECCh and C + ECChP respectively. In SDS -PAGE a protective effect was observed in the myofibrillar proteins of fillets with ECChP). The results indicate that the C + ECCh and C + ECChP treatments extend the shelf life of 3–5 days with respect to microbiological properties and 4–5 days with respect to physicochemical characteristics. A reduction in lipid and protein oxidation products was also observed during refrigerated storage. With these findings, this is considered a promising method to increase the shelf life of fish fillets combined with refrigeration and we are able to recommend this technology for the fish processing industry.

Effect of chitosan coating containing Nepeta pogonosperma extract on shelf life of chicken fillets during chilled storage

Chicken meat is highly susceptible to microbial and chemical spoilage due to its high moisture and protein content. The use of edible coatings contains herbal extracts with antioxidant and antibacterial properties that help to extend the shelf life of meat products. In this study, the effect of chitosan coating (2%) and Nepeta pogonosperma extract (NPe) (0.2% and 0.6%) and their combination on chemical properties (pH, peroxide value (PV), thiobarbituric acid index (TBARS), total volatile basic nitrogen (TVB-N)) and microbial (aerobic mesophilic and psychrotrophic microorganisms, lactic acid bacteria, Enterobacteriaceae and Pseudomonas sp.) of chicken fillets were studied over a 12-day refrigerated storage period compared to the control sample. The results of NPe DPPH radical scavenging activity (DRSA) showed that IC50 and total phenolic contents values were 94.65 μg/ml and 113.53 mg GAE/g extract, respectively. Statistical results showed that the rate of increase in pH, PV, TBARS, and TVB-N of all coated treatments were lower than control. Microbial analysis results showed a decrease in the growth of different bacteria in chitosan-treated combined with NPe compared to the control sample during chilled storage. Chicken fillets coated with chitosan and 0.6% NPe displayed a longer shelf life compared to other samples.

Corn Starch-Chitosan Nanocomposite Film Containing Nettle Essential Oil Nanoemulsions and Starch Nanocrystals: Optimization and Characterization

In the current study, nanocomposite films were produced based on corn starch:chitosan (CS:CH) biopolymers and the films were reinforced with nettle essential oil nanoemulsions (NEONEs) and starch nanocrystals (SNCs) to improve their physicochemical and mechanical properties. CS: CH at 70:30, 50:50, and 30:70 (w/w) ratios; SNCs at 2, 4, and 6% (w/w), and NEONEs at 0.5, 1, and 1.5% (w/w) were selected as variables. Then the various physical and mechanical attributes of chitosan-starch blended film containing SNCs and NEONEs were optimized using response surface methodology. The desirability function technique for the second-order polynomial models revealed that the following results could be achieved as the optimized treatment: water solubility of 51.56%; water absorption capacity of 128.75%; surface color of L (89.60), a (0.96), and b (1.90); water vapor permeability of 0.335 g/s Pa m, oxygen permeability of 2.60 cm3 μm/m2 d kPa; thickness of 154.41 µm, elongation at break of 53.54%; and tensile strength of 0.20 MPa at CS:CH of 38:62, SNC of 6.0%, and NEONEs of 0.41%. The nanocomposite film obtained can be employed as a novel biofunctional film with boosted physical mechanical and physical characteristics for food packaging applications.

Eugenol-chitosan nanoemulsion as an edible coating: Its impact on physicochemical, microbiological and sensorial properties of hairtail (Trichiurus haumela) during storage at 4 °C

Effects of the eugenol-chitosan nanoemulsion as an edible coating on the quality of hairtail (Trichiurus haumela) during storage at 4 °C were evaluated. For all samples, such parameters as pH, thiobarbituric acid (TBA), total volatile basic nitrogen (TVB-N), water holding capacity (WHC), electrical conductivity (EC), total bacteria count (TVC) and sensory were examined periodically. The results demonstrated that eugenol-chitosan nanoemulsion coating showed better preservative effects than chitosan nanoemulsion alone. Therefore, a coating based on eugenol-chitosan nanoemulsion could be regarded as an effective food-grade biopreservative to maintain the quality of hairtail fish and prolong its shelf life during chilled storage.

Effect of konjac glucomannan/carrageenan-based edible emulsion coatings with camellia oil on quality and shelf-life of chicken meat

The quality and safety of chicken meat are prone to deteriorate due to bacteria reproduction and oxidation reaction. In this study, the antimicrobial and antioxidant effects of KGM-KC coatings incorporated camellia oil were evaluated to extend the shelf-life of chicken meat. The result showed that the KGM/KC-CO coating significantly (P < 0.05) decreased weight loss, pH, thiobarbituric acid reactive substance (TBARS), total volatile nitrogen (TVN) and microbial counts when compared to uncoated samples. The obtained results revealed that KGM/KC-based coating incorporated with CO significantly extended the shelf-life of chicken meat by restraining the oxidation of lipid and protein, and retarding the microbial growth. The sensory evaluation showed that the addition of CO did not affect the odor of chicken meat, maintained the overall acceptability of coated samples. The shelf-life of chicken meat was extended up to 10 days using KGM/KC-based coating containing 3.5% CO at refrigeration (4 °C) compared to control samples. These results indicated CO could be used as an active agent to be dispersed in KGM/KC matrix by emulsification method, and the prepared emulsion coating had positive effects on extending the shelf-life of chicken meat.

Extraction of Tropical Fruit Peels and Development of HPMC Film Containing the Extracts as an Active Antibacterial Packaging Material

In recent years, instead of the use of chemical substances, alternative substances, especially plant extracts, have been characterized for an active packaging of antibacterial elements. In this study, the peels of mangosteen (Garcinia mangostana), rambutan (Nephelium lappaceum), and mango (Mangifera indica) were extracted to obtain bioactive compound by microwave-assisted extraction (MAE) and maceration with water, ethanol 95% and water–ethanol (40:60%). All extracts contained phenolics and flavonoids. However, mangosteen peel extracted by MAE and maceration with water/ethanol (MT-MAE-W/E and MT-Ma-W/E, respectively) contained higher phenolic and flavonoid contents, and exhibited greater antibacterial activity against Staphylococcus aureus and Escherichia coli. Thus, both extracts were analyzed by liquid chromatograph-mass spectrometer (LC-MS) analysis, α-mangostin conferring antibacterial property was found in both extracts. The MT-MAE-W/E and MT-Ma-W/E films exhibited 30.22 ± 2.14 and 30.60 ± 2.83 mm of growth inhibition zones against S. aureus and 26.50 ± 1.60 and 26.93 ± 3.92 mm of growth inhibition zones against E. coli. These clear zones were wider than its crude extract approximately 3 times, possibly because the film formulation enhanced antibacterial activity with sustained release of active compound. Thus, the mangosteen extracts have potential to be used as an antibacterial compound in active packaging.

Fresh Fish Degradation and Advances in Preservation Using Physical Emerging Technologies

Fresh fish is a highly perishable food characterized by a short shelf-life, and for this reason, it must be properly handled and stored to slow down its deterioration and to ensure microbial safety and marketable shelf-life. Modern consumers seek fresh-like, minimally processed foods due to the raising concerns regarding the use of preservatives in foods, as is the case of fresh fish. Given this, emergent preservation techniques are being evaluated as a complement or even replacement of conventional preservation methodologies, to assure food safety and extend shelf-life without compromising food safety. This paper reviews the main mechanisms responsible for fish spoilage and the use of conventional physical methodologies to preserve fresh fish, encompassing the main effects of each methodology on microbiological and chemical quality aspects of this highly perishable food. In this sense, conventional storage procedures (refrigeration and freezing) are counterpointed with more recent cold-based storage methodologies, namely chilling and superchilling. In addition, the use of novel food packaging methodologies (edible films and coatings) is also presented and discussed, along with a new storage methodology, hyperbaric storage, that states storage pressure control to hurdle microbial development and slow down organoleptic decay at subzero, refrigeration, and room temperatures.

Sustainable sources for antioxidant and antimicrobial compounds used in meat and seafood products

The contribution of food in promotion of health has become of most importance. The challenges that lie before the global food supply chain, such as climate changes, food contamination, and antimicrobial resistance may compromise food safety at international scale. Compounds with strong antimicrobial and antioxidant activity can be extracted from different natural and sustainable sources and may contribute to extend the shelf life of meat and seafood products, enhance food safety and enrich foods with additional biologically active and functional ingredients. This chapter describes the use of bioprotective cultures, essential oils, plant extracts, seaweed extracts and grape pomace compounds in production of value-added meat and seafood products with improved shelf life and safety, following the requests from the market and consumers.

Evaluation of the total volatile basic nitrogen (TVB-N) content in fish fillets using hyperspectral imaging coupled with deep learning neural network and meta-analysis

Recently, hyperspectral-imaging (HSI), as a rapid and non-destructive technique, has generated much interest due to its unique potential to monitor food quality and safety. The specific aim of the study is to investigate the potential of the HSI (430-1010 nm) coupled with Linear Deep Neural Network (LDNN) to predict the TVB-N content of rainbow trout fillet during 12 days storage at 4 ± 2 °C. After the acquisition of hyperspectral images, the TVB-N content of fish fillets was obtained by a conventional method (micro-Kjeldahl distillation). To simplify the calibration models, nine optimal wavelengths were selected by the successive projections algorithm. A seven layers LDNN was designed to estimate the TVB-N content of samples. The LDNN model showed acceptable performance for prediction of TVB-N content of fish fillet (R²p = 0.853; RSMEP = 3.159 and RDP = 3.001). The performance of LDNN model was comparable with the results of previous works. Although, the results of the meta-analysis did not show any significant difference between various chemometric models. However, the least-squares support vector machine algorithm showed better prediction results as compared to the other models (RMSEP: 2.63 and R²_p = 0.897). Further studies are required to improve the prediction power of the deep learning model for prediction of rainbow-trout fish quality.

Preparation and characterization of edible films from starch nanoparticles and chitosan

This study aimed to investigate the properties of edible films derived from the biocomposites of starch nanoparticles (SNPs) and chitosan. Chitosan was prepared in concentrations of 1.5, 2.0 and 3.0 wt%. The SNPs and film properties were investigated. The functional group of SNPs and chitosan as the edible film was evaluated. Then, the morphological structure, mechanical properties, thermal behavior and contact angles of the obtained films were also investigated. The data were subjected to a general linear model, and analysis of variance was carried out by using the SPSS version 23 software. The results from the research demonstrated that the solubility in water and the degree of swelling increased after the utilization of SNPs. Additionally, there was less tensile strength and higher elongation after the use of SNPs. Scanning electron microscopy analysis exhibited a smoother surface, and there was no formation of cracks when the starch transformed into nanoparticles. However, the addition of chitosan in SNPGC resulted in a grainy structure with irregularity on the surface of the films. Chitosan enhanced the degree of contact angles to 70.65 ± 2.90°, indicating an increase in the hydrophobicity of the films. This research suggested that the biocomposite films derived from SNPs–chitosan showed better performance.

Fabrication of halochromic smart films by immobilizing red cabbage anthocyanins into chitosan/oxidized-chitin nanocrystals composites for real-time hairtail and shrimp freshness monitoring

In this study, halochromic smart films were produced, characterized, and applied to monitor the freshness of hairtail and shrimp in real-time. Red cabbage anthocyanins (RCAs) solution illustrated significant color variations (red-pink-blue-green) in different pH environments. RCAs were successfully immobilized into chitosan (CS)/oxidized-chitin nanocrystals (OCN) composites through hydrogen bonding, and cohesive film structures were formed. When the proper concentration of RCAs was incorporated into the composites, improved water vapor permeability (WVP), oxygen permeability (OP), mechanical, UV-blocking, and antioxidant properties were observed. Moreover, the smart films exhibited distinguishable changes of color to ammonia vapor and acidic/alkaline environment within short time intervals, which were easy to discern by naked eyes. Finally, the smart films were applied to monitor the freshness of hairtail (Trichiurus lepturus) and shrimp (Penaeus vannamei). The film color changed significantly during storage time, and three stages of product freshness (fresh, medium fresh, and spoiled) were successfully differentiated. Strong correlations among three freshness indicators and two colorimetric parameters were also identified and analyzed. Overall, the smart system assembled from non-toxic and biodegradable components could contribute to monitoring the freshness of seafood, like hairtail and shrimp, in real-time.

Effects of Whey Protein Isolate-Based Film Incorporated with Tarragon Essential Oil on the Quality and Shelf-Life of Refrigerated Brook Trout

The efficiency of some films prepared from heat-denatured whey protein isolate solutions on the quality and shelf-life of brook trout samples during storage at 4 °C was studied in this research (WPIf-a film based on whey protein isolate and WPIf+2.5%TEO-a film based on whey protein isolate incorporated with 2.5% tarragon essential oil). The control and covered fish samples were periodically assessed (at 3 days) over 15 days of storage for the physicochemical (pH; EC, electrical conductivity; TVB-N, total volatile basic nitrogen; TBARS, thiobarbituric acid reactive substances; color), microbiological (TVC, total viable count; PTC, psychrotrophic count; LAB, lactic acid bacteria; H₂S-producing bacteria), and sensory properties (color discoloration; odor; overall acceptability). The WPIf+2.5%TEO has proven enhanced quality preservation effects compared to WPIf by showing lower values for physicochemical parameters, lower microbial loads, and higher sensory scores in the fish sample. All these effects have led to an extension of the sample’s shelf-life. In conclusion, the tarragon essential oil has conferred antioxidant and antimicrobial properties to the film. Thus, the WPIf+2.5%TEO could be a promising material for the packaging of fresh brook trout during refrigerated storage.

Effect of chitosan and gum Arabic with natamycin on the aroma profile and bacterial community of Australian grown black Périgord truffles (Tuber melansoporum) during storage

This study aimed to assess the effect of chitosan or gum Arabic edible coatings, with natamycin (200, 300, 400 mg/L) on the aroma profiles of Western Australian grown truffles at five storage intervals: 0, 7, 14, 21, and 28 days using solid-phase microextraction (SPME)-followed by gas chromatography-mass spectrometry (GC-MS). The population structure of the bacterial community of both untreated and chitosan-natamycin (400 mg/L) coated truffles were assessed using metagenomic sequencing analysis alongside GC-MS. The results demonstrated that all the coating treatments were able to have a positive impact in halting or delaying the changes of truffle aroma throughout the storage period, with chitosan-natamycin (400 mg/L) coating having the best preservation results compared to the other coatings. Only 9 volatile organic compounds (VOCs) were found to have significant changes in chitosan-natamycin (400 mg/L) coated truffles throughout the storage period compared to 11 VOCs in untreated controls. The result also demonstrated the gradual change of fresh truffle's bacteria communities over the storage period. Over 4 weeks of storage, the dominant bacterial classes of the truffles (α-Proteobacteria, Bacteroidia or Actinobacteria classes) were replaced by Bacteroidia, Actinobacteria, Deltaprotobacteria and γ-Proteobacteria classes. The preliminary results from this study show that edible coatings can affect the VOC and bacterial communities of the truffles which may have implications for future research into truffle preservation techniques.

Effects of nano-chitosan coatings incorporating with free /nano-encapsulated cumin (Cuminum cyminum L.) essential oil on quality characteristics of sardine fillet

Nowadays, adding biological compounds to food packaging is one of the types of active packaging. The aim of this study was to prepare a new degradable coating with free and nano-encapsulated Cumino cyminum L. essential oil (CCEO) with nanochitosan (Nch) base to evaluate the microbial, chemical and sensory properties of sardine fillet samples for 16 days at 4 °C. Nanoliposome using different soy lecithin ratios and cholesterol concentrations (60:0, 50:10, 40:20, and 30:30) and technique of thin-film hydration-sonication, were prepared with a range of 140-164 nm size. Encapsulation efficiency (EE) and distribution of nanoliposomes size were calculated 0.80-0.90 and 49.85-73.01% respectively. To coat sardine fillet samples, nanoliposomes with the lower size of droplet and higher EE percent were selected. The outcomes indicated that coating treatments can effectively inhibit microbial growth and chemical spoilage reflected at lower pH, peroxide value (PV) and thiobarbituric acid reactive substances (TBARs) (P < 0.05). In fact, the results of chemical and microbiological characteristics showed that the samples treated with nanocitosan/nano essential oil (NEO) showed the lowest value among other treatments during the experimental period, in the following, Nch-EO, Nch and control. pH, PV, TBARs, total viable counts (TVC), total pseudomonads count (TPC), and lactic acid bacteria (LAB) were 6.85, 0.03 (mg MDA/kg), 5.23 (mEq/kg), 3.67 (CFU/g), 3.47 (CFU/g), and 4.7 (CFU/g), respectively for Nch-NEO at the end of storage time. In addition, during the experimental period, the highest sensory properties were obtained for the Nch-NEO group. Encapsulation of CCEO reduces the rate of diffusion, thus increasing antimicrobial and antioxidant activity, as well as improving sensory properties. According to the results of this study, CCEO-encapsulated nanochitosan coatings can be used as a potent coating to increase sardine shelf life.

Preparation of nanobiocomposite film based on lemon waste containing cellulose nanofiber and savory essential oil: A new biodegradable active packaging system

Lemon waste after industrial juice extraction encompasses of valuable bio-components that stimulated the development of novel and biodegradable films. Lemon waste powder (LWP) based nanobiocomposite films were prepared by incorporating different concentrations of cellulose nanofiber (CNF) (3 and 6% w/w) and savory essential oil (SEO) (1.5 and 3% w/w) in order to modify physical, mechanical and antimicrobial properties of the films. The fabricated film samples were characterized in terms of FTIR, XRD, FE-SEM and DSC analyses as well as mechanical, water vapor permeability and antimicrobial properties. FTIR and FE-SEM results indicated a good compatibility between LWP matrix and incorporated CNF and SEO. Physical and thermal analysis showed a significant effect of incorporating SEO and CNF on enhancing glass transition temperature, tensile strength and water barrier properties of the film samples. SEM analysis revealed non-uniform dispersion of CNF at higher concentration, while SEO incorporation improved the structure of the films. In addition, the LWP based films significantly showed antimicrobial properties against five food borne pathogens and this effect improved considerably by elevating the SEO loading concentration. In conclusion, LWP based nanobiocomposite films containing 3% CNF and 3% SEO could be introduced as a good candidate for development of active food packaging.

Active packaging for Salmon stored at refrigerator with Polypropylene nanocomposites containing 4A zeolite, ZnO nanoparticles, and green tea extract

In this study, three types of Polypropylene-based (PP) films (two active nanocomposites and one control film) containing zinc oxide nanoparticles (ZnO NPs), 4A zeolite (4A Z), and green tea extract (GTE) were studied as modern active packaging's that can adjust the release of antimicrobial agents. The influence of PP nanocomposite with 3% (w/w) ZnO NPs/4A Z/GTE (treatment 1) and 6% (w/w) ZnO NPs/4A Z/GTE (treatment 2) on controlling microbial growth and preserving the sensory and chemical qualities of Salmon over nine days of storage at 4 ± 1°C was evaluated. The disk diffusion test revealed inhibition zones in the range of 10.98 ± 0.03 to 13.42 ± 0.01 m for treatments 1 and 2, respectively; the nanocomposite film with 6% ZnO NPs/4A Z/GTE had the highest antimicrobial effect against Gram-negative bacteria (p < .05). Chemical analysis revealed that the initial peroxide value of Salmon was 0.68 ± 0.0 mEq/kg, which increased by day 9 to 12.3 ± 0.03 mEq/kg in the control sample, but rising only to 9.9 ± 0.01 and 7.3 ± 0.02 mEq/kg in treatments 1 and 2, respectively (p < .05). The shelf life of Salmon given treatment 2 increased significantly to nine days relative to the control. Accordingly, these nanocomposite films are promising as new active packaging for preventing microbial growth and preserving the quality of salmon.

The effect of Macro and Nano-emulsions of cinnamon essential oil on the properties of edible active films

The effect of Nano-emulsion (NE) and Macro-emulsion (ME) of cinnamon essential oil (CEO) on the properties of carboxymethyl cellulose (CMC)-based films was investigated. MEs (diameters of 242-362 nm) and NEs (diameters of 59-80 nm) of CEO were produced through Ultra-Turrax and Ultrasonication, respectively. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) images showed different morphologies in the films containing ME and NE, also a denser and more uniform microstructure was observed in the NE films in comparison with the ME ones. The higher stability of NE in the CMC matrix, increased the thickness of the resulted films. The water vapor permeability (WVP) was increased from 2.59 × 10-9 g/ms Pa in the control film to 4.43 × 10-9 g/m s Pa in the ME film, and decreased to 1.80 × 10-9 g/ms Pa in the NE film. Adding CEO led to more flexible films with enhanced strain at break (SAB) from 53.56% in the control film to 80% and 94.77% in the ME and NE films, respectively. The antifungal indices against A. niger and M. racemous were 14.16% and 20.82% in the ME films, and were improved to 18.81% and 25% in the NE ones.

A New Cold-Active Glucose Oxidase From Penicillium: High-Level Expression and Application in Fish Preservation

Glucose oxidase (GOx) with high enzyme activity at low temperature (4°C) is potentially useful for food preservation, especially for aquatic products preservation. A cold-active GOx with approximately 83% similarity to known protein sequences, was isolated from Penicillium sp. MX3343 and expressed in Pichia pastoris X33. Through high cell density fermentation, the yield of recombinant enzyme (named GOxP5) reached 458.6 U/mL. GOxP5 showed optimal activity at 30°C and pH 5.5, and was stable at a broad pH range from pH 2-6. Moreover, GOxP5 could maintain 72% maximum activity at 4°C, suggesting its application for the preservation of aquatic products at low-temperatures. Importantly, GOxP5 showed a good antimicrobial effect against common fish pathogenic bacteria (Listeria monocytogenes and Vibrio parahaemolyticus). Moreover, sensory, microbiological (total bacterial count), and physicochemical (total volatile basic nitrogen and pH) systematic analyses proved GOxP5 to be an excellent freshness preserving agent in the context of the grass carp. These favorable enzymatic properties of GOxP5 make it potentially useful in food biopreservation, and the effect was better compared to the commonly used chemical preservatives.

Effects of Different Salt Concentrations on Several Freshness Indicators of North Pacific Squid (Ommastrephes sloani pacificus) during Storage at 4°C

ABSTRACT

The effects of salt treatment (2% [w/w] low salt and 6% [w/w] high salt) and storage time (0 to 12 days) on two biogenic amines (histamine and tyramine), total volatile base nitrogen (TVB-N), pH, and volatile compounds of the North Pacific squid during storage at 4°C were evaluated. The freshness of squid muscle was evaluated by monitoring the changes in these indicators during storage. Results showed that histamine and tyramine contents increased with storage time (4.29 to 22.47 mg/kg for histamine and 28.10 to 135.78 mg/kg for tyramine) and that, in samples treated with salt, formation of these amines can be effectively inhibited (P < 0.05) compared with untreated samples. The overall pH level initially decreased and then increased during storage (ranging from 6.49 to 7.13), and the pH level of the two salt treatment groups was a little lower than that of the control group. The TVB-N value increased with time and was effectively inhibited by salt (P < 0.05). The number and content of the volatile components in squid varied during the entire storage time. The main volatile components detected in North Pacific squid were aliphatic hydrocarbons, alcohols, aldehydes, ketones, acids, esters, aromatic hydrocarbons, phenols, nitrogenous compounds, sulfo compounds, and esters. Several compounds, such as trimethylamine, butyric acid, and sulfureted hydrogen, can be used to determine the quality of aquatic products, and salt treatment can inhibit their formation. The TVB-N value was significantly correlated with pH level and with the concentrations of histamine, tyramine, and several volatile compounds in all samples (P < 0.05). In summary, salt concentration had a positive effect on extending the shelf life of North Pacific squid, and multiple indicators should be used to determine the quality of squid.

HIGHLIGHTS

Potential of Propolis Extract as a Natural Antioxidant and Antimicrobial in Gelatin Films Applied to Rainbow Trout (Oncorhynchus mykiss) Fillets

Usage of edible films and coatings alone or incorporated with natural extracts are a new approach to preservation and packaging of food. In this study, therefore, the microbiological, chemical quality, and sensorial changes of rainbow trout fillets coated with gelatin films supplemented with propolis extract (PE) (2, 8, 16%), as a source of polyphenols, were determined during 15 days of refrigerated storage (4 ± 1 °C). According to peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) assays, lipid oxidation was delayed in the fillets coated with gelatin films incorporated with PE comparing with the control and gelatin-coated (without PE) fillets. The total volatile basic nitrogen (TVB-N) value of rainbow trout fillets showed an increase in all groups at the end of storage, observing the lowest values in the fillets coated with gelatin films prepared with 16% PE. Gelatin films enriched with PE had great inhibitory effects on the microbial growth in rainbow trout fillets. The addition of PE enhanced the effectiveness of gelatin films and delayed the lipid oxidation and sensory and microbial deterioration in trout fillets coated with these films. Thus, PE can be recommended to be used as a natural antioxidant and antimicrobial additive with gelatin films to maintain rainbow trout fillet quality.

Biodegradable Antimicrobial Food Packaging: Trends and Perspectives

This review presents a perspective on the research trends and solutions from recent years in the domain of antimicrobial packaging materials. The antibacterial, antifungal, and antioxidant activities can be induced by the main polymer used for packaging or by addition of various components from natural agents (bacteriocins, essential oils, natural extracts, etc.) to synthetic agents, both organic and inorganic (Ag, ZnO, TiO2 nanoparticles, synthetic antibiotics etc.). The general trend for the packaging evolution is from the inert and polluting plastic waste to the antimicrobial active, biodegradable or edible, biopolymer film packaging. Like in many domains this transition is an evolution rather than a revolution, and changes are coming in small steps. Changing the public perception and industry focus on the antimicrobial packaging solutions will enhance the shelf life and provide healthier food, thus diminishing the waste of agricultural resources, but will also reduce the plastic pollution generated by humankind as most new polymers used for packaging are from renewable sources and are biodegradable. Polysaccharides (like chitosan, cellulose and derivatives, starch etc.), lipids and proteins (from vegetal or animal origin), and some other specific biopolymers (like polylactic acid or polyvinyl alcohol) have been used as single component or in blends to obtain antimicrobial packaging materials. Where the package's antimicrobial and antioxidant activities need a larger spectrum or a boost, certain active substances are embedded, encapsulated, coated, grafted into or onto the polymeric film. This review tries to cover the latest updates on the antimicrobial packaging, edible or not, using as support traditional and new polymers, with emphasis on natural compounds.