The effect of essential oils on microbial composition and quality of grass carp ( Ctenopharyngodon idellus ) fillets during chilled storage

Inhibition mechanism of crude lipopeptide from Bacillus subtilis against Aeromonas veronii growth, biofilm formation, and spoilage of channel catfish flesh

Aeromonas veronii is associated with food spoilage and some human diseases, such as diarrhea, gastroenteritis, hemorrhagic septicemia or asymptomatic and even death. This research investigated the mechanism of the growth, biofilm formation, virulence, stress resistance, and spoilage potential of Bacillus subtilis lipopeptide against Aeromonas veronii. Lipopeptides suppressed the transmembrane transport of Aeromonas veronii by changing the cell membrane's permeability, the structure of membrane proteins, and Na+/K+-ATPase. Lipopeptide significantly reduced the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) by 86.03% and 56.12%, respectively, ultimately slowing Aeromonas veronii growth. Lipopeptides also restrained biofilm formation by inhibiting Aeromonas veronii motivation and extracellular polysaccharide secretion. Lipopeptides downregulated gene transcriptional levels related to the virulence and stress tolerance of Aeromonas veronii. Furthermore, lipopeptides treatment resulted in a considerable decrease in the extracellular protease activity of Aeromonas veronii, which restrained the decomposing of channel catfish flesh. This research provides new insights into lipopeptides for controlling Aeromonas veronii and improving food safety.

Study on preservation and monitoring effect of sodium alginate-konjac glucomannan films loaded with tea polyphenols and Lycium ruthenicum anthocyanins

To investigate the efficacy of sodium alginate-konjac glucomannan (SA-KGM) films with anthocyanins (LRA) and tea polyphenols (TP) in meat, beef and grass carp were selected as representative meat products for preservation and freshness monitoring experiments at 4 °C. Concurrently, storage experiments of the films were conducted in this controlled environment. The results of the storage experiment showed that the films delayed meat spoilage by 2-4 days, nearly doubling the preservation time compared to the blank control. Additionally, the film exhibited significant capability to monitor the spoilage process of beef and grass carp. It was revealed by curve fitting analysis that there was a significant correlation between the color change of the film and the spoilage index of the meat. Throughout the storage experiment with the film, it was observed that moisture significantly influenced the microstructure and bonding situation of the films, thereby impacting their mechanical and barrier properties. However, the films were still able to maintain satisfactory physicochemical properties in general. The above findings were crucial in guiding the promotion of the film within the food preservation industry.

Preservative effect of gelatin/chitosan-based films incorporated with lemon essential oil on grass carp (Ctenopharyngodon idellus) fillets during storage

The present study investigated the effect of fish gelatin/chitosan-based (FG/CS-based) films incorporated with lemon essential oil (LEO) on grass carp fillets in terms of moisture status, total volatile basic nitrogen (TVB-N), and microbial community succession during chilled (4 °C) and iced (0 °C) storage. Low-field nuclear magnetic resonance (LF-NMR) revealed that the active films remarkably inhibited moisture transformation from being the immobilized to free water in grass carp fillets, accompanied with the reduced T22 relaxation time. Besides, magnetic resonance imaging (MRI) detected a higher density of proton in the treated fish samples, indicating that the active films could improve the water-holding capacity of fish samples. Moreover, high-throughput 16S rRNA sequencing suggested that the FG/CS-based films loaded with LEO efficiently decreased the relative abundance of the bacterial genera Shewanella and Aeromonas in grass carp fillets, with minimal accumulation of TVB-N during storage. Additionally, the low storage temperature (0 °C) could further enhance the preservative effect of the active films on the fish samples, which together prolonged their shelf-life to 18 days. Overall, the combination of the active films and iced storage could provide a promising strategy to preserve grass carp fillets.

Dynamic Changes in the Microbial Composition and Spoilage Characteristics of Refrigerated Large Yellow Croaker (Larimichthys crocea) during Storage

The quality changes, dynamic changes in microbial composition, and diversity changes in large yellow croaker (Larimichthys crocea) during 4 °C refrigeration were studied using 16S rDNA high-throughput sequencing technology, and the total viable count (TVC), total volatile basic nitrogen (TVB-N), and thiobarbituric acid-reactive substances (TBARS) were determined. The results revealed a consistent increase in TVC, TVB-N, and TBARS levels over time. On the 9th day, TVC reached 7.43 lg/(CFU/g), while on the 15th day, TVB-N exceeded the upper limit for acceptable quality, reaching 42.56 mg/100 g. Based on the 16S rDNA sequencing results, we categorized the storage period into three phases: early storage (0th and 3rd days), middle storage (6th day), and late storage (9th, 12th, and 15th days). As the storage time increased, both the species richness and diversity exhibited a declining trend. The dominant genus identified among the spoilage bacteria in refrigerated large yellow croaker was Pseudomonas, accounting for a high relative abundance of 82.33%. A comparison was carried out of the spoilage-causing ability of three strains of Pseudomonas screened and isolated from the fish at the end of storage, and they were ranked as follows, from strongest to weakest: P. fluorescen, P. lundensis, and P. psychrophila. This study will provide a theoretical basis for extending the shelf life of large yellow croaker.

Degradation mechanism and development of detection technologies of ATP-related compounds in aquatic products: recent advances and remaining challenges

The degradation of ATP-related compounds is an important biochemical process that reflects the freshness of aquatic products after death. There has been considerable interest in investigating the factors affecting the degradation of ATP-related compounds in aquatic products and in developing techniques to detect them. This review provides the latest knowledge on the degradation mechanisms of ATP-related compounds during the storage of aquatic products and discusses the latest advances in ATP-related compound detection techniques. The degradation mechanisms discussed include mainly degradation pathways, endogenous enzymes, and microbial mechanisms of action. Microbial activity is the main reason for the degradation of IMP and related products during the mid to late storage of aquatic products, mainly through the related enzymes produced by microorganisms. Further elucidation of the degradation mechanisms of ATP-related compounds provides new ideas for quality control techniques in raw aquatic products during storage. The development of new technologies for the detection of ATP-related compounds has become a significant area of research. And, biosensors further improve the efficiency and accuracy of detection and have potential application prospects. The development of biosensor back-end modalities (test strips, fluorescent probes, and artificial intelligence) has accelerated the practical application of biosensors for the detection of ATP-related compounds.

Comparative analysis of the fecal microbiota of healthy and injured common kestrel (Falco tinnunculus) from the Beijing Raptor Rescue Center

The gut microbiota is a complex ecosystem that interacts with many other factors to affect the health and disease states of the host. The common kestrel (Falco tinnunculus) is protected at the national level in China. However, the available sequencing data of the gut microbiota from the feces of wild common kestrels, especially for being rescued individuals by professional organization, remains limited. In the present study, we characterized the fecal bacterial communities of healthy and injured common kestrels, and compared the structure of their fecal microbiota by analyzing the V3-V4 region of the 16S rRNA gene using high-throughput sequencing technology with the Illumina MiSeq platform. We found that Firmicutes, Proteobacteria and Actinobacteria were the most predominant phyla in common kestrels. Further, the beta diversity analysis showed that changes in gut microbes were associated with injuries to the common kestrel. The Bacteroides/Firmicutes ratio was significantly lower in the injured group. At the genus level, Glutamicibacter showed significant difference in the two groups. The aim of our current study was to characterize the basic bacterial composition and community structure in the feces of healthy common kestrels, and then compare the differences in the fecal microbiota between healthy and injured individuals. Patescibacteria, Spirochaetes, and Glutamicibacter may be studied as potential biomarkers for certain diseases in raptors. The results could provide the basic data for additional research on the fecal microbiota of common kestrels and contribute to the rescue of wild raptors in the future.

Plant essential oils improve growth performance by increasing antioxidative capacity, enhancing intestinal barrier function, and modulating gut microbiota in Muscovy ducks

Essential oils (EO) are known for their antioxidant, anti-inflammatory, antimicrobial, and growth-promoting properties. However, data rgarding their impact on the intestinal health and gut microbiota of ducks remain limited. Thus, this study aimed to investigate the effects of plant EO on the growth performance, intestinal health, and gut microbiota of Muscovy ducks. A total of 360 healthy male Muscovy ducks aged 1 d were randomly divided into 4 groups with 6 replicates and 15 ducks per replicate. Ducks were fed basal diets supplemented with 0, 100, 200, or 300 mg/kg EO. The results showed that 200 mg/kg EO supplementation significantly (P < 0.05) increased the final body weight and average daily gain, while significantly (P < 0.05) decreased the feed conversion ratio during the 56-d experimental period. Furthermore, dietary 200 mg/kg EO significantly (P < 0.05) enhanced antioxidant capacity and immune function and improved the barrier function of the intestine. Additionally, 16S rDNA sequencing analysis results showed that 200 mg/kg EO favorably modulated the cecal microbial diversities and composition evidenced by the increased (P < 0.05) the abundances of short-chain fatty acid-producing bacteria (e.g., Subdoligranulum and Shuttleworthia) and decreased (P < 0.05) abundances of potential enteric pathogenic bacteria (e.g., Alistipes, Eisenbergiella, and Olsenella). The relative abundance of beneficial bacteria was positively correlated with antioxidant, immune, and barrier function biomarkers. Overall, these findings revealed that dietary supplementation with 200 mg/kg EO had several potentially beneficial effects on the growth performance of Muscovy ducks by improving antioxidant capacity, enhancing the intestinal barrier function and favorably modulating gut microbiota.

Elucidating the role of two types of essential oils in regulating antibiotic resistance in soil

Although several approaches for reducing antibiotic resistance genes (ARGs) in soil have been proposed, the application of environmentally friendly approaches is now attracting much more attention. In the present study, two types of essential oils (EOs), namely lavender essential oil (LEO) and oregano essential oil (OEO), were selected to investigate their roles in regulating ARGs in soil. In a 28-day microcosm experiment, it was found that the different types and doses of EOs significantly changed the composition of microbial communities. The LEO treatments enriched more taxa belonging to Actinobacteria than the control, whereas the low dose of OEO reduced Actinobacteria enrichment. Besides, the control and the treatments with a high dose of LEO and OEO all significantly enriched the functional pathways related to Human Diseases, which were positively associated with ARGs. However, the low dose of these EOs helped to reduce the pathways. Because of inhibition of the functional pathways and ARG hosts, the low dose of OEO reduce the ARGs related to antibiotic efflux by 71.8% and the resistance genes to multidrug by 56.4%, but these roles did not occur in LEO treatments. These outcomes provide practical and theoretical support for the application of EOs in remediating ARG-contaminated soils.

Development and characterization of starch‑sodium alginate-montmorillonite biodegradable antibacterial films

The biodegradable antibacterial composite film blended with starch and sodium alginate was developed by solution casting method, using montmorillonite as the fortifier and star anise oil as the bacteriostat. Infrared analysis showed that montmorillonite and star anise oil were successfully incorporated into starch and sodium alginate to form a stable composite film. The addition of 6 wt% montmorillonite could enhance several properties of the films, including barrier properties, optical properties, thermal stability and mechanical properties. Meanwhile, the incorporation of star anise oil made the composite films have antibacterial properties to resist E. coli. Packing cherry tomatoes with starch‑sodium alginate-montmorillonite-star anise oil composite film could reduce the weight loss rate and decay rate of fresh cherry tomatoes. Soil burial experiments showed that the composite films exhibited a continuous biodegradation process. The starch‑sodium alginate-montmorillonite-star anise oil films decomposed into little pieces and were completely mixed in the soil within 22 days, which offered an application foreground for the development of biodegradable food packaging film with bacteriostatic activity.

Technological strategies for the use of plant-derived compounds in the preservation of fish products

New approaches to reducing synthetic preservatives in the preservation of foods draw the attention of plant-derived bioactive compounds, especially for application in foods highly susceptible to spoilage, such as fish products. The review presents relevant data from procurement, application, and methodological research trends to investigate the potential effects of plant-derived bioactive compounds on shelf life extension in fish products. The systematization of data allowed observation that the different methods of extraction and application of bioactive plant compounds result in different effects, such as the reduction of lipid oxidation, antimicrobial effects, and maintenance of sensory characteristics, benefiting the extension of shelf life. In general, plant-derived bioactive compounds are an alternative for the preservation of fish products; however, approaches to the composition of the compounds can contribute to the optimization and efficiency of the process from a technical point of view and industrial viability.

A Review of Regulatory Standards and Advances in Essential Oils as Antimicrobials in Foods

As essential oils (EOs) possess GRAS status, there is a strong interest in their application to food preservation. Trends in the food industry suggest consumers are drawn to environmentally friendly alternatives and less synthetic chemical preservatives. Although the use of EOs has increased over the years, adverse effects have limited their use. This review aims to address the regulatory standards for EO usage in food, techniques for delivery of EOs, essential oils commonly used to control pathogens and molds, and advances with new active compounds that overcome sensory effects for meat products, fresh fruits and vegetables, fruit and vegetable juices, seafood, dairy products, and other products. This review will show adverse sensory effects can be overcome in various products by the use of edible coatings containing encapsulated EOs to facilitate the controlled release of EOs. Depending on the method of cooking, the food product has been shown to mask flavors associated with EOs. In addition, using active packaging materials can decrease the diffusion rate of the EOs, thus controlling undesirable flavor characteristics while still preserving or prolonging the shelf life of food. The use of encapsulation in packaging film can control the release of volatile or active ingredients. Further, use of EOs in the vapor phase allows for contact indirectly, and use of nanoemulsion, coating, and film wrap allows for the controlled release of the EOs. Research has also shown that combining EOs can prevent adverse sensory effects. Essential oils continue to serve as a very beneficial way of controlling undesirable microorganisms in food systems.

Unraveling the effect of the combination of modified atmosphere packaging and ε-polylysine on the physicochemical properties and bacterial community of greater amberjack (Seriola dumerili)

The combined effect of ε-polylysine (PL) and modified atmosphere packaging (MAP; 60% CO2/40% N2) on the bacterial community of greater amberjack filets and their physicochemical properties was evaluated at 4°C. The total viable counts (TVC), psychrotrophic bacterial count, sensory index, texture analysis, and total volatile basic nitrogen (TVB-N) revealed that PL, MAP, and MAP + PL treatment delayed the deterioration of greater amberjack filets. These treatment groups also showed decreased accumulation of biogenic amines. High-throughput 16S rRNA gene sequencing results indicated that these treatments suppressed the growth of Pseudomonas in greater amberjack filets. Furthermore, the MAP + PL treatment group was observed to be more effective than the PL and MAP groups, extending the shelf life of greater amberjack filets by 6 days. This investigation showed that the combination of PL and MAP has the potential to retain the quality and extend the shelf life of greater amberjack.

Development of a Multifunctional Edible Coating and Its Preservation Effect on Sturgeon (Acipenser baeri♀× Acipenser schrenckii♂) Fillets during Refrigerated Storage at 4 °C

Although many coatings and films can improve the quality and shelf life of fish fillets during refrigerated storage, a more multifunctional coating material is needed. In this study, an edible alginate/protein-based coating solution was prepared by incorporating antimicrobial agents. The coating properties were characterized and its effects on the quality and shelf life of sturgeon fillets during refrigeration (4 °C) were investigated. Compared with sodium alginate coating (2% sodium alginate + antibacterial agents, H), the composite coatings (2% sodium alginate + antibacterial agents + 1:15 or 1:10 protein solution, HP-15 and HP-10) exhibited a more stable structure and better light, gas, and water barrier properties, and showed better quality-preservation effects on sturgeon fillets. The composite coatings treatments, especially HP-10 composite coating, exhibited significant (p < 0.05) effects in inhibiting microbial growth, maintaining sensory quality, reducing the production of total volatile basic nitrogen (TVB-N), decreasing nucleotide breakdown, and delaying the lipid oxidation and protein degradation in fillets. These findings confirm that the composite coatings can be used as a multifunctional coating material for freshness preservation of sturgeon fillets to improve quality and extend shelf life.

An Update on Effectiveness and Practicability of Plant Essential Oils in the Food Industry

Consumer awareness and demands for quality eco-friendly food products have made scientists determined to concentrate their attention on sustainable advancements in the utilization of bioactive compounds for increasing safety and food quality. Essential oils (EOs) are extracted from plants and exhibit antimicrobial (antibacterial and antifungal) activity; thus, they are used in food products to prolong the shelf-life of foods by limiting the growth or survival of microorganisms. In vitro studies have shown that EOs are effective against foodborne bacteria, such as Escherichia coli, Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus. The growing interest in essential oils and their constituents as alternatives to synthetic preservatives has been extensively exploited in recent years, along with techniques to facilitate the implementation of their application in the food industry. This paper’s aim is to evaluate the current knowledge on the applicability of EOs in food preservation, and how this method generally affects technological properties and consumers’ perceptions. Moreover, essential aspects concerning the limitation of the available alternatives are highlighted, followed by a presentation of the most promising trends to streamline the EOs’ usability. Incorporating EOs in packaging materials is the next step for green and sustainable foodstuff production and a biodegradable method for food preservation.

Effect of a chitosan coating incorporating epigallocatechin gallate on the quality and shelf life of bighead carp (Aristichthys nobilis) fillets during chilled storage

The objective of this study was to investigate the potential application of chitosan coatings incorporating epigallocatechin gallate (EGCG) for preserving fillets of bighead carp during chilled storage. The fillets were coated with acetic acid and glycerol, chitosan, and chitosan-EGCG, respectively, and the changes in their physicochemical, microbiological, and sensory characteristics during storage at 4 °C were determined. Notably, total volatile basic nitrogen, thiobarbituric-acid-reactive substances, and K value of chitosan-EGCG coated fillets sampled on day 15 were 48.04 %, 60.19 %, and 32.91 % lower than untreated fillets, respectively. Microbial enumeration suggested that the inclusion of EGCG significantly improved the inhibitory effect of pure chitosan coating on the proliferation of microorganisms. Furthermore, the chitosan-EGCG coated fillets also performed the best in terms of color, texture, and sensory analysis, and extended the shelf-life of the fillets for at least 6 days. A principal component analysis further confirmed the preserving effect of the chitosan-EGCG coating. Mantel test results suggested that the fillets' organoleptic characteristics strongly correlated with physicochemical and microbiological indicators. Overall, this work provides an effective protocol for food quality control and the extension of shelf life during chilled storage, and it clarifies the relationships between organoleptic characteristics and physicochemical and microbiological indexes.

In-Vitro Study on the Antibacterial and Antioxidant Activity of Four Commercial Essential Oils and In-Situ Evaluation of Their Effect on Quality Deterioration of Pacific White Shrimp (Litopenaeus vannamei) during Cold Storage

The antioxidant and antibacterial properties of four essential oils (oregano essential oil (OEO), tea tree essential oil (TTEO), wild orange essential oil (WOEO), and clove leaf essential oil (CLEO)) were determined. The in-vitro experiment indicated that CLEO had the highest total phenolic content and DPPH scavenging activity, and OEO displayed the highest antibacterial effect, so they were applied to maintain the quality of shrimp for further study. In-situ study, the total viable counts of shrimp were inhibited from 9.05 log CFU/g to 8.18 and 8.34 log CFU/g by 2% of OEO and CLEO treated alone on 10 d. The melanosis ratio was also retarded from 38.16% to 28.98% and 26.35% by the two essential oils. The inhibitory effects of OEO and CLEO on the increase of PPO activity, weight loss, and TCA-soluble peptides, and the decreasing tendency of whiteness, the contents of myofibrillar and sarcoplasmic proteins were also founded. The samples treated with 1% OEO + 1% CLEO had better quality than those treated alone. Therefore, the combination of OEO and CLEO had a synergistic effect, which displayed the highest efficiency to prevent the melanosis, bacterial growth, and protein hydrolysis of shrimp.

Influence of Multi-Frequency Ultrasound-Assisted Freezing on the Freezing Rate, Physicochemical Quality and Microstructure of Cultured Large Yellow Croaker (Larimichthys crocea)

The purpose of this work was to investigate the influence of multi-frequency ultrasound-assisted immersion freezing (UIF) on the freezing speed, quality attributes, and microstructure of cultured large yellow croaker (Larimichthys crocea) with different ultrasound powers. The findings revealed that UIF under multi-frequency conditions greatly enhanced the speed of food freezing. The multi-frequency UIF reduced the thawing and cooking losses, total volatile base nitrogen, K-values, and thiobarbituric acid reactive substances values, and increased the water holding capacity. The microstructure observation showed that multi-frequency UIF at 175 W reduced pore diameter and ice crystal size. Free amino acids analysis revealed that the application of multi-frequency UIF reduced the accumulation of bitter amino acids, and UIF-175 treatment increased the accumulation of umami amino acids. Therefore, multi-frequency UIF at a suitable ultrasonic power can remarkably improve the quality of large yellow croaker.

Effects of chitosan and apple polyphenol coating on quality and microbial composition of large yellow croaker (Pseudosciaena crocea) during ice storage

BACKGROUND

Large yellow croaker (Pseudosciaena crocea) has important commercial value because of its high nutritional value and delicious taste. However, large yellow croaker is readily affected by microorganisms during storage, which causes the corruption of muscle tissue. Both chitosan (CS) and apple polyphenols (APs) are bio-preservatives, which can effectively inhibit the growth of microorganisms and improve the quality of large yellow croaker. The effects of 10.0 and 20.0 g L^-1 CS combined with 1.0 g L^-1 AP coating on the quality and microbial composition of large yellow croaker during ice storage were investigated respectively.

RESULTS

CS + AP coating restrained the increase of total volatile basic nitrogen (TVB-N) and biogenic amines, slowed down the rise of K-value and retarded the growth of microorganisms. The bacteriostatic effect was positively correlated with the concentration of CS. Through the analysis of high-throughput sequencing (HTS), the microbial diversity was changed respectively. The proportion of Shewanella was significantly decreased by CS + AP coating treatment and Pseudomonas was the dominant microorganism in spoiled samples. Compared with the shelf-life of the control group (8 days), 20.0 g L^-1 CS combined with 1.0 g L^-1 AP coating treatment could extend the shelf-life of large yellow croaker for another 8 days.

CONCLUSIONS

CS combined with AP coating may be considered a promising method to delay the biochemical changes of ice stored large yellow croaker and extend its shelf life. © 2021 Society of Chemical Industry.

Effects of Chitosan-Grafted-Phenolic Acid Coating on Quality and Microbiota Composition of Vacuum-Packaged Sea Bass (Lateolabrax japonicus) Fillets during Chilled Storage

ABSTRACT

The aim of this research was to experimentally assess the effect of chitosan (CS)-grafted phenolic acid (CS-g-PA) derivatives on the quality and microbiota composition of vacuum-packaged sea bass (Lateolabrax japonicus). Samples were treated by deionized water (CK), 1% CS, 1% CS-g-PA copolymer, and 1% CS-grafted gallic acid (CS-g-GA) copolymer for 10 min and combined with vacuum packaging stored at 4°C to analyze the microbiological and physicochemical indicators; they were also combined with 16s RNA high-throughput sequencing to explore the effects of CS derivatives on quality and microbial composition. The results showed that the treatment of CS-g-GA and CS-g-PA could retard the increase of pH, total volatile basic nitrogen, and the K value. The degradation of ATP-related compounds, production of biogenic amines, and growth of spoilage bacteria were inhibited by CS-g-GA and CS-g-PA. Moreover, CS-g-GA and CS-g-PA performed better in the inhibition of lipid oxidation by the analysis of thiobarbituric acid reactive substances and relative fluorescence intensity. According to the results of high-throughput sequencing, the diversity of microbial composition in all groups was decreased significantly during chilled storage, especially in the CK group. The predominant microorganism was Acinetobacter in the middle period of storage, while Pseudomonas and Shewanella became predominant at the end of storage. The treatment of CS-g-GA and CS-g-PA had significant effects inhibiting the growth of Shewanella during storage. On the basis of the analysis of the microorganism and physicochemical quality, compared with the CK group, CS-g-GA and CS-g-PA can maintain the good quality of sea bass fillets and prolong the shelf life for another 12 days.

HIGHLIGHTS

Unraveling the Effects of Biochemical Drivers on the Bacterial Communities and Volatile Profiles in Refrigerated Sturgeon Filets at 4°C

Spoilage bacteria seriously influence the flavor and quality of fish meat. In this study, we investigated the quality characteristics, bacterial community, and volatile profiles of refrigerated (4°C) sturgeon filets during 10-day storage. On day 10, the refrigerated samples showed the lowest bacterial diversity and the largest difference in microbiota and biochemistry. The dominant genera in the fresh samples were Macrococcus, Acinetobacter, Moraxella, Brucella, and Pseudomonas, while the dominant bacteria changed into Acinetobacter, Carnobacterium, Macrococcus, Pseudomonas, and Psychrobacter at the end of storage. Our results suggest that these dominant taxa contribute to the spoilage of the refrigerated sturgeon filets. Meanwhile, during the storage, total viable counts, total volatile basic nitrogen, thiobarbituric acid-reactive substances, and trichloroacetic acid-soluble peptide significantly increased (P &lt; 0.05), while the sensory score decreased steadily. Additionally, the ATP-related compounds and the K-value showed similarly increasing trends. The shelf-life of the refrigerated sturgeon filets was less than 8 days. The gas chromatography–ion mobility spectrometry results suggest that hexanal, ethyl acetate, ethanol, butanal, 1-propanol, isopentyl alcohol, 2-pentanone, 2-heptanone, ethyl propanoate, and propyl sulfide are potential chemical spoilage markers. The predicted metabolic pathways indicated an abundant carbohydrate metabolism and amino metabolism in the refrigerated sturgeon filets. This study provides insight into the determinants of sturgeon shelf-life and the spoilage process involved in refrigerated fish.

Effect of a chitosan-based nanocomposite containing ZnO and Zataria multiflora essential oil on quality properties of Asian sea bass (Lates calcarifer) fillet

This research aimed to estimate the effects of chitosan (CH) coating in combination with zinc oxide nanoparticles (ZnONPS) and Zataria multiflora essential oil (ZEO) on the bacterial and biochemical properties of the Asian sea bass (Lates calcarifer) fillets during refrigeration storage (4 ± 1 °C). The fillets were randomly divided into five treatments (CH, CH-ZnONPS, CH-ZEO, CH-ZnONPs-ZEO, and control). Then, the treated fillets were kept at 4 °C and quality analysis was performed on days 0, 4, 8, 12, and 16. The results revealed that the combination of ZnONPs and ZEO with CH coating is an active coating with antimicrobial effects. Also, the coated fillets improved the biochemical properties (such as FFA, TBA, TVBN, pH) as well as color properties during refrigeration storage. The highest rate of FFA (3.59 ± 0.08%oleic acid), TBA (1.43 ± 0.00 mg MDA/kg), TVBN (30.82 ± 0.30 mg/N100g), and pH (7.38 ± 0.03) was recorded in control fillets while the lowest rate of FFA (2.19 ± 0.00%oleic acid), TBA (0.61 ± 0.00 mg MDA/kg), TVBN (19.60 ± 0.20 mg/N100g), and pH (6.99 ± 0.04) was recorded in CH-ZnONPs-ZEO coated fillets (p < 0.05) on day 16. The sensory acceptance score was better than that of the control treatment on days 8 and 12 in Sea bass fillet coated with CH-ZnONPs, and CH-ZnONPS/CH-ZEO, respectively, and it was lower the critical score for fishery products. The combination of nanoparticles or essential oils (individually or in combination together) with edible coatings (chitosan) could increase and optimize the storage time of refrigerated seafood.

Lipid oxidation and antioxidant delivery systems in muscle food

Lipid oxidation accelerates quality deterioration in muscle-based foods (fish, red meat, and poultry), resulting in off-odors/flavors, color problems, texture defects, and safety concerns. Adding antioxidants is one approach to control lipid oxidation, and several delivery strategies have been applied, such as supplementing antioxidants to the feed, direct mixing into minces, or, for whole muscle pieces; spraying, glazing, and injection. However, some issues linked to these technologies hinder their wide utilization, such as low effectiveness, noncompatibility with clean label, and off-flavor. These shortcomings have promoted the development of new antioxidant delivery technologies. In this review, the main focus is on the principles, characteristics, and implementation of five novel antioxidant delivery methods in different types of muscle food products. Their advantages and drawbacks are also summarized, plus comments about future trends in this area. Among novel routes to deliver antioxidants to muscle foods are, for whole tissues, recyclable dipping solutions; for minces, encapsulation; and, for both minces and whole tissues, cross-processing with nonmuscle antioxidant-containing raw materials as well as applications of edible films/coatings and active packaging. Advantages of these technologies comprise, for example, low price, the possibility to control the antioxidant release rate, overcoming strong aromas from natural antioxidants, and allowing antioxidant-containing raw materials from the food industry to be valorized, providing an opportunity for more circular food production.

Preparation of three-layer flaxseed gum/chitosan/flaxseed gum composite coatings with sustained-release properties and their excellent protective effect on myofibril protein of rainbow trout

Plant essential oils lose their activity due to unstable chemical properties and volatility, and the coating can improve their stability by encapsulating. The three-layer coatings were prepared by tape casting method with flaxseed gum (FG) and chitosan (CS) as film-forming materials, eugenol (EG) and laurel essential oil (LEO) as preservatives. The composite coatings were characterized, and their physicochemical properties, release properties, antibacterial and antioxidant properties were determined. Meanwhile, the protective effect of the composite coatings on rainbow trout fillets myofibril protein was studied. The mechanical properties of the FG/CS/FG coatings are better than FG coating. The release of EG and LEO from the coatings are followed simple diffusion mechanism. After added essential oils, the antibacterial and antioxidant properties of the composite coatings are significantly enhanced. In the preservation process of the rainbow trout fillets, the composite coatings can reduce the carbonyl content, increase the sulfhydryl content and Ca²⁺-ATPase activity. The β-sheet content is 6.09%-15.63% higher than that of control, indicating the coatings are helpful to maintain the order of myofibril protein. The composite coatings slowed down the decrease of antioxidant enzyme activity, thus delay the protein oxidation. Because of long-term antibacterial and antioxidant properties, the composite coatings have potential value in food preservation or food packaging materials.

Vacuum impregnation of chitosan coating combined with water-soluble polyphenol extracts on sensory, physical state, microbiota composition and quality of refrigerated grass carp slices

Herein, the effects of chitosan (CH) coating with different water-soluble polyphenol extracts (pomegranate peel (PPE), grape seed (GSE) and green tea (GTE)) through vacuum impregnation on the quality retention and microflora of refrigerated grass carp fillets were studied. Generally, the quality degradation of carp fillets was remarkably alleviated using coatings when compared to the control. As suggested by microbial enumeration and high-throughput sequencing, protective coatings were conductive to inhibit bacteria growth, especially spoilage bacteria of Pseudomonas. As a result, the indicator related to bacteria such as total volatile basic nitrogen (TVB-N) and K value had lower levels in coating groups than that in control. In addition, coating also slowed down the deterioration of physical properties of color, texture and water holding capacity in fillets, giving fillets a better edible quality. By contrast, the fillets treated by composite coatings had better quality during storage when compared to chitosan coating alone, and a relatively good synergistic antibacterial effect between chitosan and extracts was also observed, especially for CH-GTE. Overall, the best performance to inhibit quality deterioration was recorded in CH-GTE, with the lowest values of TVB-N, TBARS, K-value and water loss, and highest values of shear force and sensory preference among groups.

Effects of trans-anethole supplementation on serum lipid metabolism parameters, carcass characteristics, meat quality, fatty acid, and amino acid profiles of breast muscle in broiler chickens

This study investigated the effects of trans-anethole (TA) supplementation on the carcass characteristics, meat quality, fatty acid, and amino acid profiles of breast muscle in broilers. A total of 40 one-day-old male broiler chicks (Arbor Acres) were randomly allocated to 5 treatments, respectively, fed a corn-soybean basal diet supplemented with 0 (control), 200, 400, 600, and 800 mg TA/kg diet for 42 d. 600 mg/kg of TA supplementation decreased (P < 0.05) serum triglycerides (TG) on d 21 and d 42, and high density lipoprotein cholesterol (HDL-C) concentration on d 21, but increased (P < 0.01) serum HDL-C concentration on d 42. Dietary supplementation of TA increased (P < 0.01) the half chamber rate (HCR) and eviscerated rate (ER) of broilers. The drip loss (storing 24 and 48 h) and cooking loss of breast muscle in 600 mg/kg TA groups were lower (P < 0.05) than those in control group. The concentration of palmitoleic acid, daturic acid, oleic acid, linoleic acid, α-Linolenic acid, eicostrienoic acid, and pentosapentanoic acid (EPA), MUFA, and PUFA in the breast muscle were higher (P < 0.05) in the 600 mg/kg of TA group compared with other groups. Dietary inclusion of 600 mg/kg of TA also increased (P < 0.05) the concentration of Met, Thr, Asp, Ser, and Glu in breast muscle, tended to increase (P = 0.069) the Lys concentration. In conclusion, results indicated that TA inclusion improved the lipid metabolism, meat quality, fatty acid composition, and amino acid profile of breast muscle in broilers.

Identification of the Specific Spoilage Organism in Farmed Sturgeon (Acipenser baerii) Fillets and Its Associated Quality and Flavour Change during Ice Storage

Hybrid sturgeon, a popular commercial fish, plays important role in the aquaculture in China, while its spoilage during storage significantly limits the commercial value. In this study, the specific spoilage organisms (SSOs) from ice stored-sturgeon fillet were isolated and identified by analyzing their spoilage related on sensory change, microbial growth, and biochemical properties, including total volatile base nitrogen (TVBN), thiobarbituric acid reactive substances (TBARS), and proteolytic degradation. In addition, the effect of the SSOs on the change of volatile flavor compounds was evaluated by solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). The results showed that the Pseudomonas fluorescens, Pseudomonas mandelii, and Shewanella putrefaciens were the main SSOs in the ice stored-sturgeon fillet, and significantly affect the odors by changing the volatile compounds in the sturgeon. Compared with the fresh sturgeon, the appreciable increase of polycyclic aromatic hydrocarbons and tetramethyl-pyrazine might be the spoilage indicators of the sturgeon contaminated by P. fluorescens; the appreciable increase of 1-octen-3-ol and (z)-2-penten-1-o might be the potential marker of the sturgeon contaminated by P. mandelii; and the appreciable increase of 1-(3,3-dimethylbicyclo [2.2.1] hept-2-yl)-ethanon and butylated hydroxytoluene were associated with S. putrefaciens. This study reveals the relationship between the SSOs and flavor changes in sturgeon fillets, which will contribute to the sturgeon preservation and shelf-life extension.

Effects of multi-frequency ultrasound on the freezing rates, quality properties and structural characteristics of cultured large yellow croaker (Larimichthys crocea)

This research evaluated the effects of multi-frequency ultrasound assisted freezing (UAF) on the freezing rate, structural characteristics, and quality properties of cultured large yellow croaker. The freezing effects with triple ultrasound-assisted freezing (TUF) at 20, 28 and 40 kHz under 175 W was more obvious than that of single ultrasound-assisted freezing (SUF) at 20 kHz and dual ultrasound-assisted freezing (DUF) at 20 and 28 kHz. The results showed that UAF significantly increased the freezing rate and better preserved the quality of frozen large yellow croaker samples. Specifically, the quality parameters of the TUF-treated samples were closer to those of the fresh samples, with greater texture characteristics, a larger water holding capacity (lower thawing loss and cooking loss), lower K values and lower thiobarbituric acid reactive substances values. Light microscopy observation images revealed that the ice crystals formed by TUF were fine and evenly distributed, resulting in less damage to the frozen large yellow croaker samples. Therefore, multi-frequency UAF could improve the quality properties of the large yellow croaker samples.

Effects of star anise (Illicium verum Hook.f.) essential oil administration under three different dietary energy levels on growth performance, nutrient, and energy utilization in broilers

This experiment was conducted to investigate the effect of star anise essential oil (SAO) supplementation in diets with different energy levels on growth performance, nutrient metabolic efficiency of broilers. One hundred and ninety-two Arbor Acres male broiler chicks at 28 days of age were divided into a 3 × 4 factorial arrangement design with three dietary energy levels (13.41, 12.82, 12.23 MJ/kg) and 4 levels of SAO supplementation (0, 200, 400, and 600 mg/kg of diet). Dietary supplementation with SAO increased (p < .05) apparent metabolic efficiency of CP, EE, GE, and all of the amino acids except Trp. Significant interactions were noted between energy level and SAO administration for metabolic efficiency of CP, all of the amino acids except Cys. Inclusion of SAO enhanced apparent nutrient metabolic efficiency of broilers in a dose-dependent manner, birds supplemented with 400 mg/kg of SAO in high-energy diets appeared to contain highest nutrient metabolic efficiency, moreover, the metabolic efficiency of nutrients in low-energy diets along with 200 or 400 mg/kg of SAO was similar with that in high-energy diets without SAO, which indicated that the SAO might ameliorate the negative effects of reduced dietary metabolic energy on nutrient utilization in broilers.

Effect of Active Coatings Containing Lippa citriodora Kunth. Essential Oil on Bacterial Diversity and Myofibrillar Proteins Degradation in Refrigerated Large Yellow Croaker

The research evaluated the effects of locust bean gum (LBG) and sodium alginate (SA) active coatings containing 0.15, 0.30 or 0.60% lemon verbena (Lippa citriodora Kunth.) essential oil (LVEO) on the bacterial diversity and myofibrillar proteins (MPs) of large yellow croaker during refrigerated storage at 4 °C for 18 days. Variability in the dominant bacterial community in different samples on the 0, 9th and 18th day was observed. Pseudomonas and Shewanella were the two major genera identified during refrigerated storage. At the beginning, the richness of Pseudomonas was about 37.31% and increased for control (CK) samples during refrigerated storage, however, the LVEO-treated samples increased sharply from day 0 to the 9th day and then decreased. LBG-SA coatings containing LVEO treatments significantly delayed MPs oxidation by retarding the formation of free carbonyl compounds and maintaining higher sulfhydryl content, higher Ca²⁺-ATPase activity, better organized secondary (higher contents of α-helix and β-sheet) and tertiary structures during refrigerated storage. The transmission electron microscope (TEM) images showed that the integrity of the sarcomere was damaged; the boundaries of the H-, A-, and I-bands, Z-disk, and M-line were fuzzy in the CK samples at the end of storage. However, the LVEO-treated samples were still regular in appearance with distinct dark A-bands, light I-bands, and Z-disk. In brief, LBG-SA active coatings containing LVEO treatments suggested a feasible method for protecting the MPs of large yellow croaker during refrigerated storage.

Comprehensive Evaluation on the Use of Thymus vulgaris Essential Oil as Natural Additive against Different Serotypes of Salmonella enterica

Essential oils were proposed as natural additives to ensure food safety and quality in a more sustainable approach. The chemical composition of Thymus vulgaris essential oil (TV-EO) collected from Morocco, its antioxidant and antimicrobial activity against different serotypes of Salmonella enterica subsp. enterica was investigated. A mathematical model was implemented to predict the Salmonella behavior when exposed to TV-EO. In situ antimicrobial activity and sensory influence were tested in minced poultry meat experimentally contaminated with Salmonella and treated with TV-EO. Hydrodistillation was used to extract TV-EO, and gas chromatography-mass spectrometry (GC-MS) analysis found thymol as the most representative compound. Results of the antioxidant activity showed an IC50 of 0.29 ± 0.04 mg/mL, EC50 of 0.74 ± 0.08 mg/mL, and RC50 of 0.59 ± 0.06 mg/mL. All the Salmonella strains were susceptible to TV-EO with performing results for the disc diffusion method (inhibition diameters ranged between 24 ± 0.4 mm and 32 ± 0.6 mm), determination of minimum inhibitory concentration (MIC; 0.5%) and minimum bactericidal concentration (MBC; 1%), sublethal-injured cells (7.99 ± 0.08%), in situ activity (growth inhibition after 3 days), and meat sensory preservation (up to 1 week). The implemented mathematical model well fitted the Salmonella growth curve. TV-EO with significant antioxidant and antibacterial activities was suitable to ensure food safety and quality consistent with the new sustainable trends in the food field.

Recent advances in the application of microalgae and its derivatives for preservation, quality improvement, and shelf-life extension of seafood

Seafood is a highly perishable food product due to microbiological, chemical, and enzymatic reactions, which are the principal causes of their rapid quality deterioration. Therefore, ever-increasing consumers' demand for high-quality seafood along with a negative perception of synthetic preservatives creates opportunities for natural preservatives such as microalgae extracts. They are potential alternatives to reduce microbial growth, increase oxidative stability, and protect the sensorial properties of seafood. Research has shown that the inclusion of microalgae extracts into the aquatic animal's diet could enhance their meat quality and increase production. This review focuses on the direct application of various microalgae extracts as seafood preservative, and their functional properties in seafood, such as antioxidant and antimicrobial activities. Besides, the potential nutritional application of microalgae extracts as an alternative in aqua-feed and their impact on seafood quality (indirect application) are also presented. The safety aspects and regulatory issues of products from microalgae are highlighted.

The volatile flavor compounds of Shanghai smoked fish as a special delicacy

In this work, the effects of substrates on volatile flavor compounds of Shanghai smoked fish (SSF) from grass carp was investigated by head space-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) by changing the ratios of soy sauce (15%-25%) to white sugar (10%-20%) and replacing white sugar with reducing sugar (glucose, fructose, and ribose). The results showed the key volatile flavor compounds (ROAV ≥ 1) of SSF were 2,4-decadienal, p-xylene, nonanal, and 1-octen-3-ol with the relative contents of 10.33, 1.14, 4.84, and 1.76%, respectively. Furthermore, the existence of soy sauce had an enhancing role in the production of pyrazines, but no significant difference in white sugar. The contents of isovaleraldehyde and benzeneacetaldehyde were increased when white sugar was replaced with glucose, octanol, and 2-pentyl furan for fructose, no obvious difference in ribose. Moreover, the optimal ratios of soaking solutions were 20% soy sauce and 15% white sugar based on the scoring method of sensory evaluation. This study will provide a theoretical basis for the formation of volatile flavor compounds of SSF. PRACTICAL APPLICATIONS: Grass carp usually grows in freshwater such as pond or lake, but bacteria with earthy smell are easily attached to plankton such as diatom and cyanobacteria leading to the accumulation of bad odor substances through the food chain. Shanghai smoked fish (SSF) deeply loved by public is a traditional special dish with crispy crust and delicious taste. The attractive flavor of grass carp could be increased with the help of the Maillard reaction (MR) and seasonings. Therefore, the effect of the MR on the volatile flavor compounds of SSF was investigated by HS-SPME-GC/MS in this work. A detailed study on the volatile flavor compounds of Shanghai smoked fish could not only enrich the theoretical knowledge of flavor chemistry of freshwater fish, but have a profound contribution to the development of freshwater fish processing techniques.

The microbial safety of fish and fish products: Recent advances in understanding its significance, contamination sources, and control strategies

Microorganisms play a crucial and unique role in fish and fish product safety. The presence of human pathogens and the formation of histamine caused by spoilage bacteria make the control of both pathogenic and spoilage microorganisms critical for fish product safety. To provide a comprehensive and updated overview of the involvement of microorganisms in fish and fish product safety, this paper reviewed outbreak and recall surveillance data obtained from government agencies from 1998 to 2018 and identified major safety concerns associated with both domestic and imported fish products. The review also summarized all available literature about the prevalence of major and emerging microbial safety concerns, including Salmonella spp., Listeria monocytogenes, and Aeromonas hydrophila, in different fish and fish products and the survival of these pathogens under different storage conditions. The prevalence of antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs), two emerging food safety concerns, is also reviewed. Pathogenic and spoilage microorganisms as well as ARB and ARGs can be introduced into fish and fish products in both preharvest and postharvest stages. Many novel intervention strategies have been proposed and tested for the control of different microorganisms on fish and fish products. One key question that needs to be considered when developing and implementing novel control measures is how to ensure that the measures are cost and environment friendly as well as sustainable. Over the years, regulations have been established to provide guidance documents for good farming and processing practices. To be more prepared for the globalization of the food chain, harmonization of regulations is still needed.