Cold-induced denaturation of muscle proteins in hairtail (Trichiurus lepturus) during storage: Physicochemical and label-free based proteomics analyses

Effects of interactions between microorganisms and lipids on inferior volatile compound production during cold storage of grouper (Epinephelus coioides)

The interaction between microorganisms, proteins, and lipids plays a critical role in the odor production of fish. To explore the specific impact of the interaction between lipids and microorganisms on the overall odor of grouper, this study excluded the influence of proteins and assessed lipid (POV and TBARS) and microbial characteristics (biofilm mass and ATP content) in lipid solutions. The Results showed that microbial growth and lipid oxidation mutually promote each other. Lipidomics analysis identified 44 differential lipids, and microbial diversity analysis pinpointed five key microorganisms (Carnobacterium, Pseudomonas, Gluconacetobacter, Vagococcus, and Shewanella). Furthermore, 20 key volatile compounds (VOCs) related to odor changes in the grouper lipid solution were identified using HS-SPME-GC-MS. Correlation network analysis revealed potential microbial and lipid contributions to VOC categories, including alcohols, aldehydes, ketones, and nitrogen- and sulfur-containing compounds. This study provides new insights into the roles of microorganisms and lipids in flavor formation, offering valuable knowledge for improving seafood quality control.

Comparative analyses of physicochemical and volatile flavor characteristics in hooked, trawl-net, and radar-net hairtail (Trichiurus haumela) muscles during long-term cryopreservation at -18°C

Chemical analysis showed that pH, b* values, myosin turbidity, carbonyl content, and surface hydrophobicity elevated in hooked, trawl-net, and radar-net hairtail (Trichiurus haumela, HH, TH, and RH) muscles with the prolonged cryopreservation time (-18℃, 120 d). In contrast, L*, a* values, textural properties, and myosin solubility existed decreasing trends. Microstructural results showed that freezing resulted in disordered myofibrils, decreased collagen fibers, widened myofibrillar space, and increased fragmentation in hairtail muscles. Furthermore, volatile flavor analysis suggested that aldehydes, ketones, alcohols, and amines were the key factors for the overall flavor formation in hairtails during cold storage. Pearson correlation coefficient analysis revealed that the color, texture, and protein oxidation had close correlations with VOCs. Among the three different kinds of hairtail, fresh RH fillets exhibited an attractive aroma with high economic value, long-term frozen TH muscle tissues were prone to deterioration in texture, microstructure, and flavor, and the HH samples presented stable quality characteristics and storage performance.

Changes in the Physicochemical Properties and Microbial Communities of Air-Fried Hairtail Fillets during Storage

This study assessed the physicochemical properties of air-fried hairtail fillets (190 °C, 24 min) under different storage temperatures (4, 25, and 35 °C). The findings revealed a gradual decline in sensory scores across all samples during storage, accompanied by a corresponding decrease in thiobarbituric acid reactive substances (TBARS) and total viable count over time. Lower storage temperatures exhibited an effective capacity to delay lipid oxidation and microbiological growth in air-fried hairtail fillets. Subsequently, alterations in the microbiota composition of air-fried hairtail fillets during cold storage were examined. Throughout the storage duration, Achromobacter, Escherichia-Shigella, and Pseudomonas emerged as the three dominant genera in the air-fried hairtail samples. Additionally, Pearson correlation analysis demonstrated that among the most prevalent microbial genera in air-fried hairtail samples, Achromobacter and Psychrobacter exhibited positive correlations with the L* value, a* value, and sensory scores. Conversely, they displayed negative correlations with pH, b* value, and TBARS. Notably, air-fried samples stored at 4 °C exhibited prolonged freshness compared with those stored at 25 °C and 35 °C, suggesting that 4 °C is an optimal storage temperature. This study offers valuable insights into alterations in the physicochemical properties and microbial distribution in air-fried hairtail fillets during storage, facilitating the improvement of meat quality by adjusting microbial communities in air-fried hairtail fillets.

Effects of Quality Enhancement of Frozen Tuna Fillets Using Ultrasound-Assisted Salting: Physicochemical Properties, Histology, and Proteomics

Salting pretreatment is an effective method to improve the quality of frozen fish. This study investigated the quality changes and proteomic profile differences of frozen yellowfin tuna fillets pretreated with ultrasound-assisted salting (UAS) and static salting (SS). This study was centered on three aspects: physicochemical indicators' determination, histological observation, and proteomic analysis. The results showed that UAS significantly increased yield, salt content, and water-holding capacity (WHC), decreased total volatile base nitrogen (TVBN) compared to SS (p < 0.05), and significantly increased water in the protein matrix within myofibrils. Histological observations showed that the tissue cells in the UAS group were less affected by frozen damage, with a more swollen structure and rougher surface of myofibrils observed. Furthermore, 4D label-free proteomics revealed 56 differentially abundant proteins (DAPs) in UAS vs. NT comparison, mainly structural proteins, metabolic enzymes, proteasomes, and their subunits, which are associated with metabolic pathways such as calcium signaling pathway, gap junction, actin cytoskeletal regulation, and necroptosis, which are intimately associated with quality changes in freeze-stored tuna fillets. In brief, UAS enhances the potential for the application of salting pretreatment to improve frozen meat quality, and 4D label-free proteomics provides knowledge to reveal the potential links between quality and molecular changes in processed frozen meat to optimize future UAS meat processing.

Effect of different stunning methods on antioxidant status, myofibrillar protein oxidation, and gelation properties of large yellow croaker during postmortem

Post-mortem muscle biochemical processes play a crucial role on fish fillets quality and they are strictly linked to stunning methods. The improper stunning methods before slaughter could cause the fish to deteriorate more quickly during cold storage. This study aimed to investigate the effect of stunning methods (hit on the head, T₁; gill cut, T₂; immersion in ice/water slurry, T₃; CO₂ narcosis, T₄; 40% CO₂ + 30 % N₂ + 30% O₂, T₅) on myofibrillar proteins (MPs) of large yellow croaker. The results indicated that T₂ and T₃ samples were significantly damaged compared with other samples, which reflected that the activities of total superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly damaged during cold storage in T₂ and T₃ samples. And the gill cut and immersion in ice/water slurry resulted in the generation of protein carbonyl, the decrease of Ca²⁺-ATPase, free ammonia and protein solubility, and the production of dityrosine during storage. In addition, MPs gel of T₂ and T₃ samples showed the decrease of water hold capacity (WHC) and whiteness, structure destruction, and water migration. The T₄ samples had the least damage of MPs and gel structure during cold storage.

Lipid oxidation in foods and its implications on proteins

Lipids in foods are sensitive to various environmental conditions. Under light or high temperatures, free radicals could be formed due to lipid oxidation, leading to the formation of unstable food system. Proteins are sensitive to free radicals, which could cause protein oxidation and aggregation. Protein aggregation significantly affects protein physicochemical characteristics and biological functions, such as digestibility, foaming characteristics, and bioavailability, further reducing the edible and storage quality of food. This review provided an overview of lipid oxidation in foods; its implications on protein oxidation; and the assessment methods of lipid oxidation, protein oxidation, and protein aggregation. Protein functions before and after aggregation in foods were compared, and a discussion for future research on lipid or protein oxidation in foods was presented.