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Most microbial time–temperature indicators (TTIs) considered only one spoilage strain. This research compared single and dual spoilage strains‐based microbial TTI for quality changes of chilled grouper fish (Epinephelus fuscoguttatus x E. lanceolatus) fillet products during distribution. The next‐generation sequencing (NGS) and traditional plate count approach showed that Pseudomonas fragi and Vibrio parahaemolyticus were specific spoilage bacteria at 7 and 15°C. A dual‐strain TTI response provides more accurate results than a single‐strain TTI and provides an irreversible color change from yellow to reddish‐brown, showing levels of fish freshness. The microbial TTI comprises fish spoilage bacteria strains with 3 log CFU/ml, a nutrient broth supplemented with 2% NaCl as a medium, and phenol red with 0.25 mg/ml as a pH indicator. Overall, this study points to the applicability of a dual‐strain microbial TTI as a valuable tool for monitoring fish quality changes during cold chain break condition. [ABSTRACT FROM AUTHOR]

TTIs are smart labels designed to monitor food product temperature history that could be used to reflect quality throughout the cold chain. The objectives of this study are to develop a microbial TTI for vacuum-packed grouper fish fillets and then to test if TTI reflects microbiological and biochemical changes in fish fillets. Under constant and dynamic storage conditions, colour change can indicate three grades of fish freshness-very fresh, fresh, and spoiled-based on total volatile basic nitrogen (TVB-N) levels. Overall, similar activation energies observed in the time-temperature integrator (TTI) responses and the TVB-N of grouper fish fillets make the microbial TTI a good candidate for monitoring the freshness of fish products. Practical applications Temperature management in the cold chain has begun receiving more attention because unexpected temperature abuse can lead to food safety problems and a decline in consumer confidence. A precise and applicable method to indicate freshness degree for fish products is important when there is a broken cold chain. This work demonstrates that a microbial time-temperature indicator can be used to monitor the freshness of vacuum-packed fish fillets in cold chains based on TVB-N levels. This is particularly important for the fish when their microbiological and TVB-N analyses do not correlate well. [ABSTRACT FROM AUTHOR]

This study aimed to increase the antibacterial activity of chitosan-polylactic acid (PLA) composite film by adding nisin and ethylenediaminetetraacetic acid (EDTA). We evaluated the mechanical, physicochemical, and antibacterial properties of various PLA composite films, as well as the enhancement effect of PLA composite films with EDTA + nisin on the preservation of grouper fillets. Films of PLA alone, PLA plus chitosan (C5), PLA plus nisin + EDTA (EN2), and PLA plus chitosan plus nisin + EDTA (C5EN1 and C5EN2) were prepared. The addition of EDTA + nisin to the chitosan-PLA matrix significantly improved the antibacterial activity of the PLA composite film, with C5EN1 and C5EN2 films showing the highest antibacterial activity among the five films. Compared with the fish samples covered by C5, the counts of several microbial categories (i.e., mesophilic bacteria, psychrotrophic bacteria, coliforms, Aeromonas, Pseudomonas, and Vibrio) and total volatile basic nitrogen content in fish were significantly reduced in the samples covered by C5EN1. In addition, the counts of samples covered by C5EN1 or C5 were significantly lower compared to the uncovered and PLA film-covered samples. [ABSTRACT FROM AUTHOR]

This research prepared chitosan–PLA plastic films by extrusion, analyzed the physical and mechanical properties and antibacterial activity of the fabricated plastic films, and used them to preserve grouper fillet. We added chitosan (220 kDa, 93% DD) in the weight ratio of 0.5–2% into the PLA to prepare the chitosan–PLA films. With the increasing chitosan dosage, both the water vapor transmission rate and moisture content of chitosan–PLA films increased. Among the three doses of chitosan (0.5%, 1%, and 2%) added to PLA, 0.5% chitosan–PLA film had the highest antibacterial activity. This plastic film had an inhibitory efficiency of over 95% against Escherichia coli, Pseudomonas fluorescens, and Staphylococcus aureus. The action of covering the fish fillet with 0.5% chitosan–PLA film significantly reduced several microbes' counting (i.e., mesophiles, psychrophiles, coliforms, Pseudomonas, Aeromonas, and Vibrio) and total volatile basic nitrogen (TVBN) value in the grouper fillets stored at 4 °C. Thus, such action prolongs the fish fillets' shelf life to up to at least nine days, and this 0.5% chitosan–PLA film shows promising potential for preserving refrigerated fish. [ABSTRACT FROM AUTHOR]