Investigation of the Alternations in Lipid Oxidation and Lipase Activity in Air-Dried Hairtail (Trichiurus lepturus) during Chilled Storage.

The effects of water content and water activity on the lipid stability of air-dried hairtail (Trichiurus haumela) were investigated during chilled storage. Air-dried hairtail samples with high and low water contents were comparatively analyzed over 8 days of storage at 4 °C. The results indicated that the decreases in water activity and increases in the NaCl content significantly inhibited lipid oxidation in the air-dried hairtail samples. The peroxidation value (PV), conjugated diene value (CD), thiobarbituric acid reactive substance (TBARS) value, and p-anisidine value (p-AnV) of the air-dried hairtail significantly increased with the extension of storage time. The low water content significantly inhibited the activity of neutral and alkaline lipase, in addition to lipoxygenase, and retarded the rapid increases in the non-esterified fatty acid (NEFA) content in the hairtail samples. The correlation analysis results showed that the TBARS, p-AnV, and lipase activity were positively correlated in the air-dried hairtail samples, and the lower water content significantly inhibited the progress of lipid oxidation. This study offers a theoretical framework for the industrial processing and storage of air-dried hairtail products.

Effects of Sous Vide Cooking on the Physicochemical and Volatile Flavor Properties of Half-Shell Scallop (Chlamys farreri) during Chilled Storage.

This study explored the effects of sous vide (SV) cooking treatments on the physicochemical quality and volatile flavor of half-shell scallop (Chlamys farreri) during 30 d of chilled storage. The vacuum-packed scallop samples were cooked at 70 °C (SV-70) and 75 °C (SV-75) and maintained for 30 min. The samples were compared with the positive control (cooked at 100 °C for 10 min, CK). The results indicate that the total volatile basic nitrogen (TVBN), pH, texture, and malondialdehyde (MDA) content gradually increased, while the myofibrillar protein (MP) extraction rate of the CK, SV-70, and SV-75 samples significantly decreased with increasing chilled storage time. Significantly, the SV cooking treatments maintained a much higher water-holding capacity of scallop muscle, compared with the conventional cooking process at 100 °C. Additionally, the SV-75 cooking treatment maintained relatively stable TVBN, pH, and MDA content, springiness, and shearing force properties of scallop samples, especially during 0-20 d of storage. Volatile flavor analysis showed that a total of 42 volatile organic compounds (VOCs) were detected in the scallop samples, and there were no considerable differences in these VOCs between the CK and SV-75 cooked samples (0 d). Overall, the SV cooking treatments effectively maintained acceptable and stable physicochemical and volatile flavor properties of half-shell scallop samples during chilled storage.

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

Physicochemical, proteomics, and bioinformatics analyses were conducted to investigate protein profiles in Trichiurus haumela under frozen (120 d) and chilled (6 d) storage. Springiness, chewiness, myofibrillar active sulfhydryl content, and Ca2+-ATPase activity significantly decreased, suggesting that cold stress altered muscle proteins. Compared with fresh hairtail (FH), 66 common differentially abundant proteins (DAPs) had lower abundances in chilled (3 d; CSH) and frozen (120 d; FSH) hairtail, including myosin binding proteins, filamins, actinin, troponin, and muscle-restricted coiled-coil protein. Gene Ontology (GO) annotation showed DAPs were mainly involved in cellular process, cellular anatomical entity, intracellular, and binding items. Eukaryotic orthologous group (KOG) analysis revealed that changes in cytoskeleton and energy production and conversion functions dominated during cold storage, degrading the myofibril and connective tissue structures and the physicochemical performance of muscle tissues. This study presents deep insights into the protein alternation mechanisms in hairtail muscle under cold stress.

Investigation of the activity of cathepsin B in red shrimp (Solenocera crassicornis) and its relation to the quality of muscle proteins during chilled and frozen storage.

Cathepsin B is a cysteine protease that has important effects on the quality of muscle products. In this study, the changes of cathepsin B activity and its relation to muscle proteins were investigated in intact and beheaded shrimp during chilled and frozen storage. The obtained results indicated that the water holding capacity (WHC), shear force, hardness, and myofibrillar protein (MP) content all significantly decreased in both the intact and beheaded shrimp samples with increasing storage period (p < 0.05). Specifically, beheading shrimp exhibited much more stable characteristics than intact shrimp samples during both chilled and frozen storage. The enzyme activity results suggested that cold temperature and storage induced the release of cathepsin B from the lysosomes to the mitochondria, sarcoplasm, and myofibrils in the muscle tissues. Furthermore, SDS-PAGE and transmission electron microscopy (TEM) analysis revealed that beheading the shrimp greatly inhibited the dissociation of shrimp muscle proteins during storage. The current findings suggest that cathepsin B located in the head of shrimp was likely transferred to the muscle through the first abdominal segment during storage, accelerating the dissociation of the muscle proteins. Therefore, beheading the shrimp was conducive to prolonging the shelf-life of stored shrimp products.

Investigation of the changes in lipid profiles induced by hydroxyl radicals in whiteleg shrimp (Litopenaeus vannamei) muscle using LC/MS-based lipidomics analysis.

The oxidative effects of hydroxyl radical on the alterations of lipid profiles were investigated in shrimp muscle. Chemical results indicate peroxide value (PV) and thiobarbituric acid index (TBA-i) value in oxidation-treated shrimp significantly increased with oxidation time, and hydroxyl radical concentration increased, compared with those of in fresh samples. It was assumed that radical attack might induce lipid decomposition, backbone cleavage, and/or side-chain modifications. LC/MS-based lipidomics analysis revealed 835 lipids in shrimp assigned to 27 lipid classes, including 219 PCs and 98 CLs. In total, 86 and 34 differentially abundant lipids (DALs) accumulated at lower and higher levels, respectively, were identified in OS, compared with that in FS. This indicates hydroxyl radical attack altered the lipidomics profiles of shrimp muscle to a large extent. Furthermore, DALs, including CL 62:2, PC 38:3, and PE 34:9, could be considered as promising biomarkers to distinguish fresh and oxidation-treated shrimp products.

Metabolite dynamics and phytochemistry of a soy whey-based beverage bio-transformed by water kefir consortium.

Integrated metabolomic and metagenomic techniques were used to study the metabolite dynamics and phytochemistry of a soy whey-based beverage bio-transformed by water kefir consortium. The UPLC- MS/MS and HPLC-ESI-MS metabolite quantification and the OPLS-DA result showed that the kefir consortium induced a significant change in the metabolite composition and altered the phytochemistry of the fermented beverage. Bioactive peptide analogues, flavonoids, and glycerophospholipids including N-acetyl-L-phenylalanine, acetyl-DL-leucine; tephcalostan, wogonin, pelargonin, genistein, daidzein, and glycerophosphoserines (PS), glycerophosphoethanolamines (PE) respectively were synthesized while flavonoid glycosides and soyasaponins were degraded in the novel beverage. Furthermore, the beverage showed high ACE inhibitory and DPPH radical scavenging activity of 92.31% and 87.51% respectively. Lactobacillus, Saccharomyces cerevisiae, and Pichia membranifaciens were the predominant microbial groups in the new beverage as revealed by the metagenomic sequence analysis. The study thus provides discrete data evidence that kefir consortium is a viable starter for transforming soy whey into a bioactive beverage.

Effect of Co-Fermentation with Lactic Acid Bacteria and K. marxianus on Physicochemical and Sensory Properties of Goat Milk.

In this study, a multi-starters fermentation system involved lactic acid bacteria and yeasts was applied to obtain a novel acidified goat milk (AGM). Significant differences were found in the volatile flavor profile among goat milk, goat yogurt, and AGM reflected by principal component analysis of electronic nose (E-nose) data. Gas chromatography-mass spectrometry (GC-MS) results indicated that the relative content of free octanoic acid decreased, and more aromas were formed in AGM, which were considered to mask the goaty smell and give AGM a pleasant flavor. Rheological analysis indicated that AGM had higher apparent viscosity and G' and G'' moduli than goat yogurt and goat milk. Therefore, the goat yogurt fermented by lactic acid bacteria and K. marxianus exhibits a new method to alleviate the goaty flavor in goat milk and provides a novel option for those who were allergic to milk protein and dislike goaty flavor in goat milk.

Increased Phenolic Content and Enhanced Antioxidant Activity in Fermented Glutinous Rice Supplemented with Fu Brick Tea.

Glutinous rice-based foods have a long history are consumed worldwide. They are also in great demand for the pursuit of novel sensory and natural health benefits. In this study, we developed a novel fermented glutinous rice product with the supplementation of Fu brick tea. Using in vitro antioxidant evaluation and phenolic compounds analysis, fermentation with Fu brick tea increased the total phenolic content and enhanced the antioxidant activity of glutinous rice, including scavenging of 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical, 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical, and hydroxyl radical, ferric-reducing antioxidant power, and ferric ion reducing power and iron chelating capability. Besides, compared with traditional fermented glutinous rice, this novel functional food exhibited a stronger activity for protecting DNA against hydroxyl radical-induced oxidation damage. Quantitative analysis by HPLC identified 14 compounds covering catechins and phenolic acids, which were considered to be positively related to the enhanced antioxidant capability. Furthermore, we found that 80% ethanol was a suitable extract solvent compared with water, because of its higher extraction efficiency and stronger functional activities. Our results suggested that this novel fermented glutinous rice could serve as a nutraceutical food/ingredient with special sensory and functional activities.

Study of water dynamics in the soaking, steaming, and solid-state fermentation of glutinous rice by LF-NMR: a novel monitoring approach.

Solid-state fermentation (SSF) of starchy grain is a traditional technique for food and alcoholic beverage production in East Asia. In the present study, low-field nuclear magnetic resonance (LF-NMR) was introduced for the elucidation of water dynamics and microstructure alternations during the soaking, steaming, and SSF of glutinous rice as a rapid real-time monitoring method. Three different proton fractions with different mobilities were identified based on the degree of interaction between biopolymers and water. Soaking and steaming significantly changed the proton distribution of the sample. The different phases of SSF were reflected by the T2 parameters. In addition, the variations in the T2 parameters were explained by the microstructure changes of rice induced by SSF. The fermentation time and T2 parameters were sigmoidally correlated. Thus, LF-NMR may be an effective real-time monitoring method for SSF in starch systems.