In this work, we studied the effects of different spray drying inlet temperatures (130, 160 and 190 ℃) on the emulsifying characteristics of bigeye tuna skin gelatin. The emulsifying properties were evaluated by determination of creaming index and emulsion microstructure, and the interface and continuous phase of different emulsions were evaluated by measurement of surface hydrophobicity and gel strength. Furthermore, the mechanism of the influence of spray drying inlet temperature on gelatin’s emulsifying characteristics was analyzed by molecular mass distribution and Fourier transform infrared spectroscopy (FTIR). The results showed that the high-molecular-mass subunits of gelatin were excessively damaged and the integrity of the triple helix structure was reduced with increasing inlet temperature of spray drying, which resulted in exposure of more hydrophilic amino acids, thereby reducing the gel strength (851.29–676.65 g) and surface hydrophobicity (218.81–82.96). The decrease in surface hydrophobicity was not conducive to the adsorption of gelatin at the oil-water interface and the formation of a tight network structure, and the decrease in gel strength indicated that the network structure in the continuous phase of the emulsion become loose, thus resulting in an increase in droplet size and creaming index as well as a decrease in emulsion stability. It can be seen that the spray drying inlet temperature is negatively correlated with the emulsion stability, and the inlet temperature should not be too high for the preparation of emulsified fish skin gelatin by spray drying, preferably at 130 ℃.

To investigate the pathogenicity of viable but non-cultivable state (VBNC) Vibrio parahaemolyticus (Vp) from salmon consumed raw, the isolated strain VBNC-VpRS1 and the virulent strain Vp17802 were separately orally administered to C57BL/6J mice. The behavior of the mice was observed for the following 72 h, and the disease activity index (DAI) score, Vp load, intestinal damage, tight junction (TJ) protein expression and cytokine levels were measured. It was found that symptoms of infection with VBNC-VpRS1 appeared six hours later than those of infection with Vp17802. Compared with the control group, infection with VBNC-VpRS1 and Vp17802 significantly increased the DAI score, colonic Vp load and the levels of proinflammatory cytokines in mice (P < 0.01 and P < 0.001), and significantly decreased the colon length, anti-inflammatory factor levels and TJ protein expression (P < 0.01, P < 0.001 and P < 0.05). The infected mice showed severe intestinal mucosal tissue defects with hemorrhagic effusion and neutrophil infiltration. Moreover, the colonic Vp load and the degree of pathologic damage in the mice infected with VBNC-VpRS1 were higher than (P < 0.05) those in the mice infected with Vp17802, whereas VBNC-VpRS1 was less effective than Vp17802 in inhibiting the intestinal barrier function and promoting inflammatory responses (P < 0.05). VBNC-VpRS1 can be resuscitated in vivo and has strong colonic adhesion and invasion abilities. As VBNC Vp seriously threatens human health, seafood products consumed raw should be included in the monitoring of Vp.

Sensory characteristics, the succession of bacterial communities and the contents of six biogenic amines during long-term fermentation (1, 2, 3 and 8 years) of shrimp paste were investigated by sensory evaluation, high-throughput sequencing and high-performance liquid chromatography (HPLC), respectively. Results showed that the color of shrimp paste turned dark brown, the L* value declined and the b* value increased then declined, and the grainy mouthfeel disappeared along with the prolongation of fermentation time. Meanwhile, the shrimp-like and ammonia-like smell decreased, and umami taste reached the maximum after two years of fermentation. The bacterial flora detected in shrimp paste comprised 600 species belonging to 894 genera in 42 phyla, with the dominant phyla being Firmicutes and Proteobacteria, and the dominant genera being Tetragenococcus, Psychrobacter, Pseudomonas, Enterococcus, Lactobacillus and Roseovarius, and the bacterial diversity reached a peak after two years of fermentation. The types and contents of biogenic amines in shrimp paste gradually increased as fermentation progressed. Putrescine, cadaverine, histamine, tyramine, spermidine and spermidine were detected in all samples after eight years fermentation. Pearson correlation analysis showed that histamine had a significantly positive correlation with Devosia (P < 0.05), but a significantly negative correlation with Bacillus, Ralstonia, Photobacterium and Staphylococcus (P < 0.01). Putrescine had a significantly positive correlation with Ralstonia (P < 0.01), buta significantly positive correlation with Pseudomonas, Roseicyclus and Sulfitobacter (P < 0.05). Acinetobacter was positively correlated with cadaverine (P < 0.01). The study provides a theoretical basis for screening functional strains and controlling biogenic amines in shrimp paste.

Bacillus subtilis JZXJ-7 isolated from shrimp paste can significantly degrade histamine under salt stress but the mechanism is unclear. This study aims to evaluate the effect of 170 and 340 mmol/L NaCl on B. subtilis JZXJ-7 growth, histamine degradation, antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST)) activities and Na⁺/K⁺-ATPase activity. Furthermore, comparative metabolomics was used to investigate histamine biodegradation mechanism by B. subtilis JZXJ-7 subjected to salt stress. Both 170 and 340 mmol/L NaCl promoted B. subtilis JZXJ-7 growth in late stages of reproduction (32−48 h), increased histamine degradation rate by 64.85% and 79.87% (P < 0.05), Na⁺/K⁺-ATPase activity to 6.28 (P < 0.05) and 11.63 U/mg (P < 0.01) respectively. NaCl treatment significantly increased the activities of CAT, GST and SOD (P < 0.05), amino acids and its metabolites (33.39%), benzene and substituted derivatives (12.05%), heterocyclic compounds (10.62%), organic acids and derivatives (9.75%), aldehydes, ketones, esters (5.59%) and nucleotides and its metabolites (4.58%). Metabolite set enrichment analysis revealed NaCl induced differential metabolic pathways of D-glutamine, D-glutamate, L-arginine, L-proline, histidine and glycerophospholipids, L-lysine degradation, and aminoacyl-tRNA biosynthesis. Exposure to 340 mmol/L NaCl up-regulated carbohydrate, glutathione and glycerophospholipid metabolism. The new insights into the mechanism of salt stress to promote B. subtilis JZJX-7 growth, energy metabolic pathways and to degrade histamine provide the theoretical basis for application of B. subtilis JZXJ-7 in food fermentation industry.

This study aimed to characterize and identify calcium-chelating peptides from rabbit bone collagen and explore the underlying chelating mechanism. Collagen peptides and calcium were extracted from rabbit bone by instant ejection steam explosion (ICSE) combined with enzymatic hydrolysis, followed by chelation reaction to prepare rabbit bone peptide-calcium chelate (RBCP-Ca). The chelating sites were further analyzed by liquid chromatography-tandem mass (LC-MS/MS) spectrometry while the chelating mechanism and binding modes were investigated. The structural characterization revealed that RBCP successfully chelated with calcium ions. Furthermore, LC-MS/MS analysis indicated that the binding sites included both acidic amino acids (Asp and Glu) and basic amino acids (Lys and Arg). Interestingly, three binding modes, namely Inter-Linking, Loop-Linking and Mono-Linking were for the first time found, while Inter-Linking mode accounted for the highest proportion (75.1%), suggesting that chelation of calcium ions frequently occurred between two peptides. Overall, this study provides a theoretical basis for the elucidation of chelation mechanism of calcium-chelating peptides.

The concept of healthiness and sustainability have triggered consumers into choosing healthier food, especially “clean-label” products. Porcine skin is a natural “clean-label” raw material, and direct usage of whole pork skin as an additive has been proven as an efficient way to deal with the by-product issues and also satisfies the “clean label” demands of consumers. However, efficient approaches to convert bulk skin into handy powders in a green-fabrication manner while maintaining its unique properties have yet to be fully investigated. Herein, we provided two green approaches, drying-grinding, and wetting-grinding, to prepare pork skin functional protein powder (FPP), and their chemical composition, structure, properties, stability, and functionality are systematically investigated. Specifically, FPP prepared by two methods exhibit similar chemical composition and great thermal stability. Notably, FPP prepared by drying-grinding method is superior in flow ability, water dispersion, and texture properties of FPP gels as compared to wetting-grinding method. Structural analyses revealed that the superior properties of FPP prepared by drying-grinding method depend on the intrinsic natural triple helix structure of collagen. Overall, this work revealed the underlying key factors for the preparation of FPP with excellent properties, and highlighted that the FPP prepared by drying-grinding method is more suitable for practical application as “clean-label” additives in the food industry.

Ultraviolet (UV)-induced photoaging skin has become an urgent issue. The functional foods and cosmetics aiming to improve skin photoaging are developing rapidly, and the demand is gradually increasing year by year. Collagen peptides have been proven to display diverse physiological activities, such as excellent moisture retention activity, hygroscopicity, tyrosinase inhibitory activity and antioxidant activity, which indicates that they have great potential in amelioration of UV-induced photoaging. The main objective of this article is to recap the main mechanisms to improve photoaging skin by collagen peptides and their physiological activities in photo-protection. Furthermore, the extraction and structural characteristics of collagen peptides are overviewed. More importantly, some clinical trials on the beneficial effect on skin of collagen peptides are also discussed. In addition, prospects and challenges of collagen peptides are emphatically elucidated in this review. This article implies that collagen peptides have great potential as an effective ingredient in food and cosmetics industry with a wide application prospect.