Shelf-life of smoked eel fillets treated with chitosan or thyme oil

New advances in biological preservation technology for aquatic products

Aquatic products, characterized by their high moisture content, abundant nutrients, and neutral pH, create an optimal environment for the rapid proliferation of spoilage organisms, lipid oxidation, and autolytic degradation. These factors collectively expedite the spoilage and deterioration of aquatic products during storage and transportation within the supply chain. To maintain the quality and extend the shelf-life of aquatic products, appropriate preservation methods must be implemented. The growing consumer preference for bio-preservatives, is primarily driven by consumer demands for naturalness and concerns about environmental sustainability. The present review discusses commonly employed bio-preservatives derived from plants, animals, and microorganisms and their utilization in the preservation of aquatic products. Moreover, the preservation mechanisms of bio-preservatives, including antioxidant activity, inhibition of spoilage bacteria and enzyme activity, and the formation of protective films are reviewed. Integration of bio-preservation techniques with other methods, such as nanotechnology, ozone technology, and coating technology that enhance the fresh-keeping effect are discussed. Importantly, the principal issues in the application of bio-preservation technology for aquatic products and their countermeasures are presented. Further studies and the identification of new bio-preservatives that preserve the safety and quality of aquatic products should continue.

Chitosan coatings containing thyme essential oil enhance the quality of snakehead (Channa striata) during chilled storage verified by metabolomics approaches

In the present study, we investigated the preservative effects of chitosan (CS) coatings, with and without thyme essential oil (TEO), combined with vacuum impregnation (VI) on maintaining the quality of snakehead fillets during chilled storage. The results showed that the VI treatment significantly inhibited drip loss, discoloration, microbial proliferation, and the accumulation of biogenic amines (BAs) in the sneakhead fillets. Compared to the control, the fillets treated with VI of 1% (w/w) CS and 1.5% (w/w) TEO (i.e., CSTEO) showed significant reductions in both psychrophiles and mesophiles, with a 2.66 log CFU/g decrease in total viable count (TVC) on day 3 and a 1.89 log CFU/g decline in TVC on day 9, respectively. In addition, the content of histamine and putrescine in the CSTEO groups was maintained at ∼1.14 and 3.23 mg/kg during the 12-day chilled storage, respectively. A total of 100 chemical compounds were tentatively identified using untargeted metabolomics approaches. The multivariate analysis further revealed that the combination of VI and CSTEO maintained fish quality mainly through preventing lipid oxidation and protein degradation. Overall, the VI-CSTEO treatment effectively maintained the fish quality during storage at 4°C, with minimum microbial proliferation and accumulation of BAs. PRACTICAL APPLICATION: The preservative effect of chitosan coatings containing thyme essential oil combined with vacuum impregnation on snakehead quality during the 12-day chilled storage was verified, and the underlying mechanisms were deciphered through integrated metabolomics approaches. Our study could provide a promising strategy for the preservation of aquatic products.

Shelf-life extension of Pacific white shrimp (Litopenaeus vannamei) using sodium alginate/chitosan incorporated with cell-free supernatant of Streptococcus thermophilus FUA 329 during cold storage

Seafood is highly perishable and has a short shelf-life. This study investigated the effect of chitosan and alginate (CH-SA) coating combined with the cell-free supernatant of Streptococcus thermophilus FUA329 (CFS) as a preservative on the quailty of white shrimp (Litopenaeus vannamei) refrigerated at 4° for 0, 3, 6, 9, 12, 15 days. Freshly shrimps were randomly divided into four groups: the CFS group (400 mL); the CH-SA group (1% chitosan/1% alginate); the CFS-CH-SA group (1% chitosan/1% alginate with 400 mL CFS) are treatment groups, and the control group (400 mL sterile water). The CFS-CH-SA coating effectively suppressed microbial growth total viable count and chemical accumulation (pH, total volatile basic nitrogen, thiobarbituric acid reactive substance) compared with the control. Additionally, the CFS-CH-SA coating improved the texture and sensory characteristics of shrimp during storage. The coated shrimp exhibited significantly reduced water loss (p < 0.05). The combination of CH-SA coating with CFS treatment can extend the shelf life of shrimp. PRACTICAL APPLICATION: Recently, edible films have received more consideration as a promising method to enhance the shelf life of seafood. The presence of Lactic acid bacteria metabolites in edible films reduces spoilage and improves consumer health. Our findings encourage the application of edible coating incorporated with cell-free supernatant of Streptococcus thermophilus FUA 329 to design multifubctional foods and preserve the qualities of shrimp.

Factors affecting the quality of frozen large yellow croaker (Pseudosciaena crocea) in cold chain logistics: Retention time and temperature fluctuation

The purpose of this study is to provide a reference for avoiding the quality loss of large yellow croaker in cold chain transportation. The effects of retention time before freezing and temperature fluctuation caused by transshipment in logistics were evaluated by TVB-N, K value, TMA value, BAs, FAAs content and protein-related characteristics. The results showed that the retention would lead to the rapid increase of TVB-N, K value, and TMA value. And the temperature fluctuation would further lead to deterioration of these indicators. We concluded that the influence of retention time was far greater than that of temperature fluctuation. In addition, the bitter free amino acids (FAAs) were highly correlated with the freshness-related indicators, which could reflect the freshness changes of samples, especially the quantity of histidine. Therefore, it is suggested to freeze samples immediately after catching and try to avoid temperature fluctuations during cold chain to maintain the quality.

Evaluation of Practical Applicability and Synergistic Effects of Bio-Based Food Packaging Materials Combined with Plant-Based Stabilisers

Different analyses and feasibility studies have been conducted on the plant extracts of thyme (Thymus vulgaris), European horse chestnut (Aesculus hippocastanum), Nordmann fir (Abies nordmanniana), and snowdrop (Galanthus elwesii) to evaluate bio-based alternatives to common petrol-based stabilisers. For this purpose, in this study, plant extracts were incorporated into poly-lactic acid films (PLA) at different concentrations. The films’ UV absorbance and migration into packed food was analysed via photometric assays (ABTS radical cation scavenging capacity assay, β-carotene assay) and GC–MS analysis. Furthermore, the synergistic antioxidant effects of various combinations of extracts and isolated active compounds were determined. This way, antioxidant effects can be increased, allowing for a highly effective use of resources. All extracts were successfully incorporated into PLA films and showed notable photoabsorbing effects, while no migration risk was observed. Depending on extract combinations, high synergistic effects of up to 726% can be utilised to improve the effectiveness of bio-based extracts. This applies particularly to tomato paste and Aesculus hippocastanum extracts, which overall show high synergistic and antioxidant effects in combination with each other and with isolated active compounds. The study shows that it is possible to create safe bio-based antioxidant films which show even improved properties when using highlighted target combinations.

Innovative Non-Thermal Technologies for Recovery and Valorization of Value-Added Products from Crustacean Processing By-Products-An Opportunity for a Circular Economy Approach

The crustacean processing industry has experienced significant growth over recent decades resulting in the production of a great number of by-products. Crustacean by-products contain several valuable components such as proteins, lipids, and carotenoids, especially astaxanthin and chitin. When isolated, these valuable compounds are characterized by bioactivities such as anti-microbial, antioxidant, and anti-cancer ones, and that could be used as nutraceutical ingredients or additives in the food, pharmaceutical, and cosmetic industries. Different innovative non-thermal technologies have appeared as promising, safe, and efficient tools to recover these valuable compounds. This review aims at providing a summary of the main compounds that can be extracted from crustacean by-products, and of the results obtained by applying the main innovative non-thermal processes for recovering such high-value products. Moreover, from the perspective of the circular economy approach, specific case studies on some current applications of the recovered compounds in the seafood industry are presented. The extraction of valuable components from crustacean by-products, combined with the development of novel technological strategies aimed at their recovery and purification, will allow for important results related to the long-term sustainability of the seafood industry to be obtained. Furthermore, the reuse of extracted components in seafood products is an interesting strategy to increase the value of the seafood sector overall. However, to date, there are limited industrial applications for this promising approach.

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.

Synergistic Antimicrobial Effectiveness of Plant Essential Oil and Its Application in Seafood Preservation: A Review

The synergistic potential of plant essential oils (EOs) with other conventional and non-conventional antimicrobial agents is a promising strategy for increasing antimicrobial efficacy and controlling foodborne pathogens. Spoilage microorganisms are one of main concerns of seafood products, while the prevention of seafood spoilage principally requires exclusion or inactivation of microbial activity. This review provides a comprehensive overview of recent studies on the synergistic antimicrobial effect of EOs combined with other available chemicals (such as antibiotics, organic acids, and plant extracts) or physical methods (such as high hydrostatic pressure, irradiation, and vacuum-packaging) utilized to reduce the growth of foodborne pathogens and/or to extend the shelf-life of seafood products. This review highlights the synergistic ability of EOs when used as a seafood preservative, discovering the possible routes of the combined techniques for the development of a novel seafood preservation strategy.

Effect of chitosan-whey protein isolated coatings incorporated with tarragon Artemisia dracunculus essential oil on the quality of Scomberoides commersonnianus fillets at refrigerated condition

The purpose of present work was to assess the effects of chitosan (CH) coating in combination with whey protein isolated (WPI) and tarragon essential oil (TEO) on the bacterial (total mesophilic (TMC) bacteria and psychrotrophic (PTC) bacteria), physicochemical (total volatile bases- nitrogen (TVB-N), pH, thiobarbituric acid reactive substances (TBARS), free fatty acid (FFA)) and sensory properties of Scomberoides commersonnianus muscle during storage at refrigerator (4 ± 1 °C). The fillet were randomly divided into seven lots and subjected to the following treatments by immersion: chitosan (CH), whey protein isolate (WPI), whey protein isolate- TEO (WPI-TEO), chitosan-TEO (CH-TEO), chitosan-whey protein isolated (CH-WPI), chitosan/whey protwin isolated+ TEO (CH/WPI + TEO) and controls, then stored at 4 °C. Results indicated that incorporation of WPI and TEO into the material coating developed active coatings with good antimicrobial agent growth inhibition activity against TMC and PTC bacteria. The coated samples also retarded the increase in the contents of TVB-N, pH, TBARS and FFA during storage. The score less than critical score of 3 was made at day 8 and 12 for fillet coated with control and coated samples except of fillets coated with chitosan, respectively. These results confirmed that the incorporation of essential oils or other biopolymers into edible coatings may improve the deterioration of chilled seafood.

Prospect of Polysaccharide-Based Materials as Advanced Food Packaging

The use of polysaccharide-based materials presents an eco-friendly technological solution, by reducing dependence on fossil resources while reducing a product's carbon footprint, when compared to conventional plastic packaging materials. This review discusses the potential of polysaccharides as a raw material to produce multifunctional materials for food packaging applications. The covered areas include the recent innovations and properties of the polysaccharide-based materials. Emphasis is given to hemicelluloses, marine polysaccharides, and bacterial exopolysaccharides and their potential application in the latest trends of food packaging materials, including edible coatings, intelligent films, and thermo-insulated aerogel packaging.

Chitosan and Oregano Oil Treatments, Individually or in Combination, Used To Increase the Shelf Life of Vacuum-Packaged, Refrigerated European Eel (Anguilla anguilla) Fillets

We investigated the impact of chitosan and oregano essential oil (EO) individually or in combination on the quality of eel fillets in vacuum packaging (VP) and stored under refrigeration (4°C). Treatments studied were (i) control eel fillets stored in VP (E), (ii) eel fillets treated with 0.3% (v/w) oregano EO and stored in VP (E-OR), (iii) eel fillets treated with 2.0% (w/v) chitosan and stored in VP (E-CH), and (iv) eel fillets treated with 2.0% (w/v) chitosan and 0.3% (v/w) oregano EO and stored in VP (E-CH-OR). Treatments E-CH-OR and E-CH significantly reduced counts of mesophilic bacteria, Pseudomonas, Shewanella, and yeasts and molds during storage. Use of chitosan alone or in combination with oregano EO led to a significant reduction in concentrations of trimethylamine nitrogen and total volatile basic nitrogen in fillets, which led to lower concentrations of thiobarbituric acid reactive substances compared with the control samples. The eel samples in the E-CH and E-CH-OR groups were sensorially acceptable during the entire refrigerated storage period of 18 days. Presence of chitosan in the E-CH and E-CH-OR fillets did not negatively affect the taste of the fillets. E-CH fillets received a higher taste score than did E-CH-OR fillets probably because of the distinct and "spicy" lemon taste of chitosan, which was well received by the sensory panel. Based on overall sensory data (based on mean sensory scores of odor and taste), the shelf life was 6 days for the control fillets, 10 days for the E-OR fillets, and >18 days for the E-CH and E-CH-OR fillets stored in VP at 4°C. Overall, chitosan-treated eel fillets had lower microbial loads and a longer shelf life compared with the controls. Chitosan-treated eel fillets were preferred over oregano-treated fillets. Chitosan alone or in combination with oregano could be used as a preservative treatment and shelf-life extender for other seafoods.

Coating Effects of ε-Polylysine and Rosmarinic Acid Combined with Chitosan on the Storage Quality of Fresh Half-Smooth Tongue Sole (Cynoglossus semilaevis Günther) Fillets

The study was to evaluate the effects of chitosan-based coating combined with rosmarinic acid (RA) with different concentrations of ε-polylysine (ε-PL) on flavor retention and sensorial properties of half-smooth tongue sole fillets during storage at 4 °C. Results showed that chitosan-based coatings combined with ε-PL and RA contributed to the reduction of off-flavor compounds, such as total volatile base nitrogen (TVB-N), trimethylamine (TMA), and ATP-related compounds, and accumulation of free amino acids (FAAs). Nineteen volatile organic compounds were analyzed by gas chromatography-mass spectrometer (GC/MS) during storage, including seven alcohols, six aldehydes, and six ketones. The coating treated fresh half-smooth tongue sole (HTS) fillets significantly reduced the relative content of off-odor volatiles, such as 1-octen-3-ol, propanal, hexanal, and octanal. According to sensory evaluation results, chitosan-based coating combined with ε-PL and RA was an effective way to maintain quality of HTS fillets during refrigerated storage.

Chitosan films incorporated with Thymus capitatus essential oil: mechanical properties and antimicrobial activity against degradative bacterial species isolated from tuna (Thunnus sp.) and swordfish (Xiphias gladius)

Chitosan-based coatings and films have been widely studied, demonstrating to be an efficient and eco-friendly approach to extend the shelf life of food products. The effect of incorporating Thymus capitatus essential oil (TCEO) at different concentrations (0.5, 1.0, and 1.5% w/w) on physical, mechanical and antimicrobial properties of chitosan films was studied. The antimicrobial activity of the films was evaluated by agar diffusion method, against 23 spoiling microorganisms isolated from tuna and swordfish (ten Shewanella baltica, one S. morhuae, one S. putrefaciens, two Pseudomonas fluorescens, two P. fragi, five Serratia spp., one Aeromonas molluscorum, and one Acinetobacter radioresistens) and Shewanella putrefaciens ATCC 49138. The films exerted antimicrobial activity against all the tested strain, although not proportional to increasing TCEO concentration. In particular, S. baltica was the most sensitive species and the inhibition was stable after 72 h. In general, TCEO incorporation in chitosan films, significantly (p < 0.05) decreased the water permeability (from 0.577 ± 0.060 gmm/kPahm² at 61% R.U. for chitosan to 0.487 ± 0.037 gmm/kPahm² for the film with 1.5% TCEO), the elongation at brake (from 27.322 ± 2.35% for chitosan to 14.695 ± 3.99% for the film with 1.5% TCEO) and increased the tensile strength (from 1.697 ± 0.16% for chitosan to 19.480 ± 2.86% for the film with 1.5% TCEO). Moisture content and water contact angle of the films also showed a similar trend with TCEO introduction, because of crosslinking reaction among the polymer chains and TCEO components. Scanning electron microscopy confirmed structure-properties relationships. These results suggest chitosan films incorporated with TCEO as an alternative treatment to inhibit the growth of degradative bacteria with potential application in the fish industry. The importance of testing more than one strain of the same bacteria species to evaluate the effectiveness of chitosan-essential oils coatings was also demonstrated.