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In this study, the correlation between protein phosphorylation and deterioration in the quality of tilapia during storage in ice was examined by assessing changes in texture, water-holding capacity (WHC), and biochemical characteristics of myofibrillar protein throughout 7 days of storage. The hardness significantly decreased from 471.50 to 252.17 g, whereas cooking and drip losses significantly increased from 26.5% to 32.6% and 2.9% to 9.1%, respectively (P < 0.05). Myofibril fragmentation increased, while myofibrillar protein sulfhydryl content and Ca 2+ -ATPase activity decreased from 119.33 to 89.29 μmol/g prot and 0.85 to 0.46 μmolPi/mg prot/h, respectively (P < 0.05). Correlation analysis revealed that the myofibrillar protein phosphorylation level was positively correlated with hardness and Ca 2+ -ATPase activity but negatively correlated with WHC. Myofibrillar protein phosphorylation affects muscle contraction by influencing the dissociation of actomyosin, thereby regulating hardness and WHC. This study provides novel insights for the establishment of quality control strategies for tilapia storage based on protein phosphorylation., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The present study evaluated the effects and underlying mechanisms of light salting on quality properties of tilapia fillets during repeated freezing-thawing. Light salting was found to improve water-holding capacity and decelerated texture softening in tilapia fillets during repeated freezing-thawing. Instead of tissue distortion and heterogeneous aggregates in control groups, light salting promoted myofibril disassembly and formation of an ordered protein network with the solubilized myofibrillar proteins. The myofibrils presented an overall amorphous appearance with the loss of M-lines, removing the restraints to myofibril swelling and solubilization from A-binds in salted groups during repeated freezing-thawing. The structural rearrangement caused by light salting facilitated the enlargement of water-holding space, transformation of tissue water, and tissue recoverability, improving water-holding capacity and texture properties of tilapia fillets during freezing-thawing. The finding provided novel insight into the improvement of quality properties of tilapia fillets by light salting when subjected to drastic temperature fluctuations., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Background: Frozen tilapia fillet has become a leading aquatic product. High drip loss, dry and fibrous mouthfeel, and an unappealing appearance are its main problems. It was hypothesized that light salting could improve the quality, and that the preparation conditions would affect the storage stability of frozen tilapia fillets., Results: The quality changes of lightly salted tilapia fillets were evaluated during frozen storage, and the underlying mechanisms were studied from the physicochemicaland microstructural perspectives. Though the salt content was 1.5% in all samples,the amount of ice crystals in frozen tissues decreased with the descending water content and freezing point (P < 0.05). No intracellular voids were observed in the samples prepared under proper salting conditions, and the myofibers were plump and smooth after freezing-thawing, which contributed to the high water-holding capacity of lightly salted fillets. After 28 days,the water-binding capacity of the salted groups was 14.69%-18.62% higher than that of their unsalted counterparts (P < 0.05). The reduced protein solubility in the salted fillets was likely to have occurred because the solubilized and unfolded proteins interacted more easily during frozen storage. The oxidation degree of myofibrillar proteins was also affected by salting condition, and the fillets with less oxidized sulfhydryl groups maintained high springiness after 28 days of frozen storage., Conclusion: The salting condition of 9% NaCl solution for 1 h was recommended for the preparation of lightly salted fillets from freshwater fish, taking into account quality, processing efficiency, and storage stability. The enhanced water-holding capacity and texture of lightly salted tilapia fillets were attributed to modified physicochemical and microstructural properties. These results could provide a scientific basis for the processing and storage of high-quality, frozen, lightly salted fillets from freshwater fish. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

The objectives of this study were to study the quality changes (ice crystal morphology, Ca 2+ -ATPase activity, total sulfhydryl [SH] content, intrinsic fluorescence intensity [IFI], and K value [freshness determination]) of tilapia at different storage temperatures for 112 days, and kinetic models and artificial neuronal network (ANN) were developed to predict the changes. There was a dramatic increase in cross-section area and equivalent diameter and a sharp decrease in Ca 2+ -ATPase activity and SH content during the first 4 weeks (p < 0.05). IFI λmax decreased by 43.95%, 29.77%, 28.97% and 18.58% after 16 weeks at 265 K, 259 K, 253 K, and 233 K. The kinetic model established by IFI λmax could be accurately described the quality changes during storage at 233-265 K. However, the prediction accuracy established by other indices decreased at later stages (14-16 weeks). The ANN model was superior to Arrhenius models and performed better for all indicators., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Collagen plays a pivotal role in human physiological functions and extracted collagen has multiple potential applications. Tilapia skin can be applied to extract collagen for maximizing the profit of tilapia processing. Electrospinning/electrospraying is novel micro- and nano-techniques to fabricate microfibers and microspheres in a simple and easy way. In this work, we extract collagens from tilapia skin by three types of extraction methods: acetic acid method, hot water method, and sodium hydroxide method. Then, these extracted collagens are characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Fourier transform infrared spectrometry. These extracted collagens have different molecular weights and different protein secondary structures. Finally, these extracted collagens are applied to fabricate electrosprayed microspheres, electrospun microfibers, and mixed microspheres/microfibers with multiple potential applications by adjusting the collagen concentrations. Higher polymer molecular weight only needs lower concentration to produce microfibers. The microfiber diameter increases with the increase of collagen concentration. This work proves that extraction methods have obvious effect on the preparation of electrospun/electrosprayed microstructures of tilapia skin collagen and provide a way to maximize resource utilization of tilapia processing waste., (Copyright © 2019 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

The evolution of quality attributes and their association with the protein properties of lightly tilapias fillets salted with different replacement proportions of NaCl with KCl (0%, 10%, 30%, 50%, 70%, 100%) at the same ionic strength were investigated. KCl replacements using optimal substitution (50% of KCl) contributed to maintaining desired quality properties. Further, KCl replacement (about 50~70% of KCl) led to the insolubilization and weakened stability of myofibrillar proteins, represented by the unfolding of the myofibrillar protein, increased surface hydrophilic points, and strengthened internal protein-protein interaction, resulting in the structurally reinforced hardness and lower water-holding capacity. Excessive replacement (more than 70% of KCl) showed apparent deterioration in taste quality, coloration, and hardness received by sensory sensation caused by immoderate hydrolysis and aggravated oxidation of the myofibrillar protein. In this sense, insights into KCl replacements on protein properties might be a positive approach to improving quality attributes of lightly salted tilapias fillets. [ABSTRACT FROM AUTHOR]

To explore an effective quality evaluation system based on microstructure changes, tilapia samples were preserved at the temperature of −20, −40, and −80°C up to a storage period of 270 days. The porous structure of fish muscle was quantified using the cross‐section area (CA) and fractal dimension (FD) of ice crystals, and the effectiveness of the two was compared. The relationships between microstructure changes and traditional quality parameters, including water‐holding capacity, texture properties, K value, and total volatile basic nitrogen (TVB‐N), were also explored. The results showed that FD dropped by 8.79, 4.53, and 3.03% of fillets at −20, −40, and −80°C after 270 days of storage, respectively. The better fitting on the basis of FD for evaluating quality of tilapia compared with CA. Traditional quality indicators were correlated well with the FD (R2 > 0.94), except for relaxation time (T2). The first‐order kinetic equation FD = exp (0.0895 t exp[−7240.26/RT])/1.8903 was developed, and FD relative errors between predicted and observed values were all less than 3%, which demonstrated that the feasibleness and accuracy of quality evaluation based on FD during frozen storage. Practical applications: Frozen storage inevitably has a negative impact on the tissue, water‐holding capacity, and protein properties of fish. Thus, it is of great urgency to put forward an effective quality evaluation system of frozen fish. Here, tilapia samples were studied over a period of 270 days by measuring their microstructure of muscle fibers and traditional quality parameters. Correlation analysis of each index was also conducted and kinetic model based on FD was established and validated finally. In addition to establishing an effective quality evaluation system based on microstructure changes for tilapia, these results will provide new insights into the quality evaluation and laid a foundation for the application of fractal dimension in tilapia processing and transportation. [ABSTRACT FROM AUTHOR]

A tandem mass tag technology (TMT), based on the quantitative proteomics approach, was applied to investigate the associations between tilapia (Oreochromis niloticus) fillet quality characteristics (pH, color, texture, ice crystal morphology and protein denaturation) and proteome profiles during a 12-month frozen storage period. When compared with the control group (0 day), a total of 175 differentially abundant proteins (DAPs) were found in tilapia muscle from two frozen storage temperatures (−20 °C and −40 °C). Correlation analysis between the DAPs and the quality traits showed that 80 DAPs were correlated closely with the quality traits. The bioinformatics analysis revealed that 49, 9 and 2 DAPs were involved in binding proteins, metabolic enzymes and protein turnover, respectively, which were mainly closely associated with color traits and protein denaturation. These results provide a further understanding of the proteome changes and mechanisms of the quality decline of tilapia during frozen storage. • A TMT-based strategy was applied to the proteomics of frozen tilapia fillets for 12 months. • Tilapia fillets stored at − 40 °C exhibited satisfactory quality traits. • Tilapia fillets stored at − 20 °C showed greater proteome changes than those stored at − 40 °C. • Twenty-nine and 17 DAPs correlated closely with color trait and protein denaturation. • Four proteins could be potential biomarkers for monitoring the quality of frozen tilapia. [ABSTRACT FROM AUTHOR]

This study aimed to develop an active biodegradable bilayer film and to investigate the release behaviors of active compounds into different food matrices. Cinnamaldehyde (CI) or thymol (Ty) was encapsulated in β-cyclodextrin (β-CD) to prepare the active β-CD inclusion complex (β-CD-CI/β-CD-Ty). The tilapia fish gelatin-sodium alginate composite (FGSA) containing β-CD-CI or β-CD-Ty was coated on the surface of PLA film to obtain the active bilayer film. Different food simulants including liquid food simulants (water, 3% acetic acid, 10% ethanol, and 95% ethanol), solid dry food simulant (modified polyphenylene oxide (Tenax TA)), and the real food (Japanese sea bass) were selected to investigate the release behaviors of bilayer films into different food matrixes. The results showed that the prepared β-CD inclusion complexes distributed evenly in the cross-linking structure of FGSA and improved the thickness and water contact angle of the bilayer films. Active compounds possessed the lowest release rates in Tenax TA, compared to the release to liquid simulants and sea bass. CI and Ty sustained the release to the sea bass matrix with a similar behavior to the release to 95% ethanol. The bilayer film containing β-CD-Ty exhibited stronger active antibacterial and antioxidant activities, probably due to the higher release efficiency of Ty in test mediums. [ABSTRACT FROM AUTHOR]

Frozen tilapia muscle-based Shanghai smoked fish without fish bones was developed using a three-stage method (salt pickling, frying, and sugar smoking), and the effect of varying salt amounts (0.5%, 1.0%, and 1.5% of muscles) was studied. The muscle with 1.0% salt had the best sensory evaluation score. Salt pickling significantly increased and then frying significantly decreased the numbers and concentrations of the volatile organic compounds (VOCs) in the muscles. Compared with the others, 1.0% salt resulted in the lowest numbers and concentrations of the VOCs in the frying stage and the highest VOC concentrations in the sugar smoking stage. Statistical analyses of VOC concentrations suggested that two VOC classes (esters and aldehydes) and 42 VOC individuals could be used to differentiate the treated tilapia muscles with different salt amounts. This work provided a basic knowledge of the effects of food processing stages and salt amounts on fish quality. • Frozen tilapia muscle-based Shanghai smoked fish without bones was developed. • The muscle with 1.0% salt had the best consumer acceptance. • VOC numbers and concentrations changed after different preparation stages. • Compared with others, 1.0% salt induced the highest VOC concentration after smoking. • Two VOC classes (esters and aldehydes) and 42 individuals had VIP scores of >1. [ABSTRACT FROM AUTHOR]