Quality enhancement of large yellow croaker (Pseudosciaena crocea) during frozen (-18 ºC) storage by spiral freezing

Development of machine learning-based shelf-life prediction models for multiple marine fish species and construction of a real-time prediction platform

At least 10 million tons of seafood products are spoiled or damaged during transportation or storage every year worldwide. Monitoring the freshness of seafood in real time has become especially important. In this study, four machine learning algorithms were used for the first time to develop a multi-objective model that can simultaneously predict the shelf-life of five marine fish species at multiple storage temperatures using 14 features such as species, temperature, total viable count, K-value, total volatile basic‑nitrogen, sensory and E-nose-GC-Ms/Ms. as inputs. Among them, the radial basis function model performed the best, and the absolute errors of all test samples were <0.5. With the optimal model as the base layer, a real-time prediction platform was developed to meet the needs of practical applications. This study successfully realized multi-objective real-time prediction with accurate prediction results, providing scientific basis and technical support for food safety and quality.

The application of ice glazing containing D-sodium erythorbate combined with vacuum packaging to maintain the physicochemical quality and sweet/umami non-volatile flavor compounds of frozen stored large yellow croaker (Pseudosciaena crocea)

Ice glazing containing 0.3 % D-sodium erythorbate (DSE), combined with vacuum packaging, was used as a method to maintain the quality of large yellow croaker during frozen storage. This study aimed to assess various aspects, including water properties (water holding capacity and moisture distribution), protein-related characteristics (secondary and tertiary structure of myofibrillar protein), freshness indicators (K value and total volatile base nitrogen (TVB-N)), and non-volatile flavor compounds (free amino acids (FAAs) and nucleotides) in samples stored for 300 days at -23 °C. The results showed that vacuum packaging had a significant inhibitory effect on the growth of ice crystal. Notably, it successfully maintained the cross-sectional area of nearly all ice crystals below 20,000 μm2, effectively curtailing water loss. Simultaneously, the combination of vacuum packaging with the complex ice glaze effectively mitigated the degradation of IMP and free amino acids, maintaining low levels of K value (12.85 %) and TVB-N (11.28 mg N/100 g) throughout the 300-day frozen storage, retaining first-class freshness. Among the various treatment modalities assessed, the combined application of vacuum packaging and 0.3 % DSE-infused ice glazing emerged as the most effective in terms of preservation outcomes. This efficacious combination shows promising potential for the frozen storage of aquatic products and is therefore recommended for practical implementation.

Integrated volatile compounds and non-targeted metabolomics analysis reveal the characteristic flavor formation of proteins in grouper (Epinephelus coioides) during cold storage

Microorganisms, lipids, and proteins always interact in a complex way in the fish matrix, which becomes a hindrance to evaluate the quality of the individual factors affecting them. In order to investigate the relationship between protein deterioration and volatile compounds (VOCs) in grouper during cold storage, the myofibril protein (MP) was used as a single-factor study to exclude microorganisms and lipids effects. The oxidation and degradation of MP during storage at 4 ℃ were evaluated, including MP content, total sulfhydryl content, carbonyl content, spatial structure and microstructure. Headspace-solid phase microextraction- gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the VOCs of grouper MP, and a total of 7 key VOCs were selected, including three ketones (2-nonanone, 2-undecanone and 2-tridecanone), three esters (methyl butyrate, methyl palmitate and methyl ester 9-octadecenoic acid) and one alcohol (3-methyl-1-butanol). At the same time, a non-targeted metabolomics method based on UPLC-Q-Extractive Orbitrap was used to investigate the changes in metabolites during MP storage. A total of 107 up-regulated differential metabolites and 7 down-regulated metabolites were annotated, and 6 metabolic pathways highly related to proteins were screened. Spearman correlation analysis showed that 7 key VOCs are associated with the biosynthesis and metabolism of ornithine and lysine. And a possible solution to protein deterioration in grouper was proposed, which provided a reference for improving protein quality and regulating flavor formation during cold storage of grouper at source.

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.

Potential of Good's buffers to inhibit denaturation of myofibrillar protein upon freezing

The current systematic study sought to examine the potential use of three Good's buffers (MES, MOPS and HEPES) in inhibiting myofibrillar protein (MFP) denaturation induced by acidity changes. The highest degree of acidity variation was found in the center and bottom of large bottles due to the freeze-concentration effect. Good's buffer tended to basify during freezing, and it could prevent the crystallization of sodium phosphate (Na-P) buffer. Acidification upon freezing Na-P disrupted the natural conformation of MFP and induced the formation of large proteins aggregates with tight packing. The 15 mM MES, 20 mM MOPS, and 30 mM HEPES were respectively added to neutralize the strong acidity drop induced by freezing 20 mM Na-P, and all of them significantly improved the stability of the MFP conformation (P < 0.05). This work is not only critical to meet the growing demand for protein, but also groundbreaking for broadening the applicability of Good's buffers in the food industry.

Evaluation on the effect of ice glazing with different compound additives on the quality of frozen stored (-23 °C) large yellow croaker (Pseudosciaena crocea)

BACKGROUND

Compounded ice glazing has been used in large yellow croaker to improve its quality during frozen storage. The ice glazing liquid is prepared by compound use of trehalose and tea polyphenols, and the moisture, protein-related properties and freshness of the fish have been evaluated during 300 days of frozen storage.

RESULTS

The results showed that the addition of trehalose effectively reduced the loss of water. At the same time, it was difficult for ice crystals to grow under the action of trehalose, the average diameter could still be maintained at 111.25-119.85 μm. The combination with tea polyphenols could effectively maintain the protein structure and keep the total volatile base nitrogen (TVB-N) and K value within 11.84 mg/100 g and 13.18%, so that the freshness of the fish was always at the first level.

CONCLUSION

In a word, the ice glazing with 5% trehalose and 8% tea polyphenols had the best preservation effect, which was recommended for the frozen storage. © 2022 Society of Chemical Industry.

Effects of Different Freezing Methods on Physicochemical Properties of Sweet Corn during Storage

Fresh sweet corn has a series of physiological and biochemical reactions after picking due to the high moisture content, leading to damaged nutritional value. Rapid freezing of sweet corn after harvest can minimize tissue damage and quality deterioration. In this study, freshly harvested sweet corn was frozen by ultrasound-assisted freezing, brine freezing, strong wind freezing, and refrigerator freezing. The effects of different freezing methods on hardness, water loss, color, epidermal structure, soluble solids content, soluble sugars content, peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activities of frozen sweet corn during storage were investigated. The results showed that brine freezing and strong wind freezing could effectively reduce the quality loss of sweet corn, keep the color, soluble sugars, and soluble solids content of the sweet corn, delay the decrease in antioxidant enzyme activity, and maintain the quality of sweet corn during long term storage.

Effects of starch/polyvinyl alcohol active film containing cinnamaldehyde on the quality of large yellow croaker (Pseudosciaena crocea) proteins during frozen storage

This study aimed to investigate the effects of starch/polyvinyl alcohol (starch/PVA) film containing cinnamaldehyde (CIN) with different humidity treatment on the quality changes of large yellow croaker (Pseudosciaena crocea) under vacuum packaging during frozen storage. It was evaluated by measuring the water loss, water migration, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), free amino acids (FAA) content, myofibril secondary and tertiary structure and microstructure of large yellow croaker. Compared with control group, the starch/PVA films could inhibit the water loss, water migration, protein degradation, lipid oxidation and microstructure damage of fish. The film containing CIN with higher humidity treatment showed the best protective effect for large yellow croaker. The film with higher humidity treatment showed better to maintain the quality of fish than that with low humidity treatment. Therefore, starch/PVA active film containing CIN with high humidity treatment showed good fresh-keeping potential in the frozen storage of aquatic products.

Effect of Gum Tragacanth-Sodium Alginate Active Coatings Incorporated With Epigallocatechin Gallate and Lysozyme on the Quality of Large Yellow Croaker at Superchilling Condition

This research was done to investigate the synergistic interactions of the gum tragacanth (GT)–sodium alginate (SA) active coatings, incorporated with epigallocatechin gallate and lysozyme, on the quality of large yellow croaker (Larimichthys crocea) during superchilling storage at −3°C. Results showed that the GT-SA active coatings, containing epigallocatechin gallate [EGCG (E), 0.32% w/v], and lysozyme [LYS (L), 0.32% w/v] have reduced the total viable count, psychrophilic bacteria, and Pseudomonas spp. by about 1.55 log CFU/g, 0.49 log CFU/g, and 1.64 log CFU/g compared to the control at day 35. The GT-SA active coatings containing EGCG and LYS were effective in lowering the formations of off-odor compounds such as total volatile basic nitrogen (TVB-N), malondialdehyde (MDA), and off-favor amino acid (histidine). The solid phase microextraction gas chromatography-mass spectrometer (SPME-GC/MS) was applied to characterize and to quantify the volatile compounds of large yellow croaker samples during superchilling storage, while the relative content of the fishy flavor compounds (including 1-octen-3-ol and acetoin) was significantly reduced in the active coatings treated samples. Furthermore, the GT-SA active coatings containing EGCG and LYS treatments was found to be more effective in retarding the migration of water based on magnetic resonance imaging (MRI) results and in maintaining the organoleptic quality of large yellow croaker in superchilling storage at −3°C according to the sensory evaluation results. The results showed that the GT-SA active coating containing EGCG and LYS was effective to be used as a fish preservative to improve the quality and to prolong the shelf life of large yellow croaker in a superchilling storage for at least 7 days.

Effects of Dual-Frequency Ultrasound-Assisted Thawing Technology on Thawing Rate, Quality Properties, and Microstructure of Large Yellow Croaker (Pseudosciaena crocea)

This research evaluated the effects of dual-frequency ultrasound-assisted thawing (UAT) on the thawing time, physicochemical quality, water-holding capacity (WHC), microstructure, and moisture migration and distribution of large yellow croaker. Water thawing (WT), refrigerated thawing (RT), and UAT (single-frequency: 28 kHz (SUAT-28), single-frequency: 40 kHz (SUAT-40), dual-frequency: 28 kHz and 40 kHz (DUAT-28/40)) were used in the current research. Among them, the DUAT-28/40 treatment had the shortest thawing time, and ultrasound significantly improved the thawing rate. It also retained a better performance from the samples, such as color, texture, water-holding capacity and water distribution, and inhibited disruption of the microstructure. In addition, a quality property analysis showed that the pH, total volatile basic nitrogen (TVB-N), and K value were the most desirable under the DUAT-28/40 treatment, as well as this being best for the flavor of the samples. Therefore, DUAT-28/40 treatment could be a possible thawing method because it improves the thawing rate and maintains the quality properties of large yellow croaker.

Effects of Freeze-Thaw Cycles on Water Migration, Microstructure and Protein Oxidation in Cuttlefish

This study was conducted to analyze the effects of multiple freeze-thaw (F-T) cycles on microstructural disruption, water migration, protein oxidation and textural properties of cuttlefish. Low-field nuclear magnetic resonance (LF-NMR) showed an increase in the proportion of free water in cuttlefish flesh. It was also observed by scanning electron microscopy (SEM) that multiple F-T cycles increased the gap between muscle fibers and disrupted the original intact and compact structure. The results of Fourier transform infrared spectroscopy, intrinsic fluorescence spectroscopy, Ca2+ATPase content, sulfhydryl content and free amino acid content indirectly prove that multiple F-T cycles can lead to the destruction of the a-helical structure of cuttlefish myofibril protein and the content of irregular curls increased, protein aggregation and degradation, and tryptophan oxidation. In addition, after repeated freezing and thawing, the water holding capacity, whiteness value, elasticity and chewiness of cuttlefish flesh decreased, the total volatile base nitrogen content increased. It can be concluded that the freeze-thaw cycles are very harmful to the quality of the frozen foods, so it is important to keep the temperature stable in the low-temperature food logistics.