Kelp is an important marine biological resource and food raw material. At present, adult kelp is eaten by people, but there is a lack of systematic studies evaluating the quality characteristics of kelp at different growth periods. In this study, the main nutritional components, amino acid composition, mineral elements, fatty acids, flavor-free amino acids and cooking texture characteristics of juvenile and adult kelp were analyzed. The results showed that the ash, protein and crude fat contents of juvenile kelp were higher than those of adult kelp. The essential amino acid (EAA)/total amino acid (TAA) ratios of juvenile kelp and adult kelp were 0.36 and 0.34, respectively, and the EAA/nom-essential amino acid (NEAA) ratios were 0.57 and 0.53, respectively. The nutrient reference values (NRV) of potassium in juvenile kelp and adult kelp were 70.40% and 41.25%, respectively, and the NRV of iron were 54.60% and 16.00%, respectively. The contents of palmitic acid, myristic acid and elaidic acid in juvenile kelp were higher than those in adult kelp. The taste activity values (TAV) of umami amino acids in juvenile kelp and adult kelp were 3.46 and 0.64, the TAV of sweet amino acids were 0.27 and 0.80, and the TAV of bitter amino acids were 0.26 and 0.00, respectively. The hardness, viscosity, chewiness, adhesiveness, cohesiveness and resilience of blanched juvenile kelp were less than those of blanched mature kelp, while their elasticity was basically the same. The above results indicate that juvenile kelp have better protein nutritional potency, mineral element and elaidic acid contents, and taste and texture characteristics than adult kelp. This study provides useful information for the high-value utilization of kelp in the modern food industry, and offers inspiration for the development of the modern food industry and the kelp industry.

Taste is an important perceptual response, and the basic tastes include sweet, sour, bitter, salty, and umami. Taste receptors are proteins that perceive various tastes. In this paper, the topical keywords on taste receptors, the sources and types of taste receptors that have been researched, the methods used for taste receptor research, and the researchers engaged in the study of taste receptors are analyzed and summarized to provide a reference for taste receptor research. Through literature analysis, it is found that bitter taste, sweet taste, sour taste, umami taste, rat, human, mouse, cell, expression, protein, induction, gene, signal, neuron and molecule are the topical keywords on research of taste receptors. The Proceedings of the National Academy of Sciences, the Journal of Neuroscience, the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology and the Journal of Comparative Neurology are the key journals in the field of taste receptors.Murine taste receptors are the object of most research in this field, but there are still large differences between murine and human taste receptors. Therefore, further research is needed to accurately understand human taste receptors. At present, taste receptors have researched at the structural biological and neurobiological levels by means of computer simulation and molecular biology experiments. The structures of the medaka fish T1R2/T1R3 ligand recognition domain, zebrafish Otop1 and chicken Otop3 and the signaling pathways of each taste receptor have been elucidated. However, the accurate structures of most receptors have not been fully understood, and it is difficult to distinguish taste nerve stimuli with different characteristics. Currently, obtaining single crystals of G protein coupled receptors (GPCRs) by protein expression, protein structure elucidation and signal transduction, and elucidating the crystal structure and the interaction mechanism between various receptors are major research directions. The United States is a leader in the field of taste receptors, and its scientists such as Ryba N. J. P., Hoon M. A., and Chandrashekar J. have led the research direction in this field. This review clarifies the current status of the field of taste receptors and predicts future trends in this field, which will hopefully provide new directions and ideas for researchers.

Dried sea bass samples were prepared with endogenous enzymatic transformation + light heat treatment (S1), endogenous enzymatic transformation + high-intensity heat treatment (S2), light heat treatment (S3) and high-intensity heat treatment (S4), and their flavor was analyzed by sensory evaluation, solid phase microextraction combined with gas chromatography-mass spectrometry (GC-MS). The correlation between volatile components and sensory attributes was investigated by partial least squares regression (PLSR). Sensory analysis showed that there were significant differences in flavor profiles between samples S1, S2, S3, and S4. The results of GC-MS showed that n-hexanal, nonanal, n-octanal, butyl phenol, 1-octene-3-ol, 2,3-octanedione, caryophyllene, and 2,6-di-tert-butyl-p-cresol were the major volatile components in dried sea bass. The volatile components of S1, S2, S3, and S4 were significantly different, and the content of volatile components in S1 and S2 was significantly higher than that in S3 and S4. PLSR analysis showed that benzaldehyde, kunienal, n-octanal, acetophenone, heptanol, and 2-ethyl hexanol were correlated with the sensory properties of dried sea perch. The contents of these substances were significantly different among the four samples. The comparison revealed that hexanal, acetophenone, and benzaldehyde in S1 and S2, enhancing the grassy and sweet aroma, were produced by the reaction between fat and amino acids under the action of endogenous enzymes. In S3 and S4, heat treatment promoted the oxidative degradation of triglycerides to produce octanal, 2-ethylhexanol, decenal and trans-2-octenal, enhancing the orange and fatty aroma. In addition, the enzymatic activity of cathepsin B was much higher in S1 and S2 than in S3 and S4. The results of this study provide a theoretical reference for optimizing the preparation process of dried sea bass and further understanding of the mechanism of the flavor formation of aquatic foods.

In order to explore the potential of flavonoids from Guanxi honey pomelo as a pancreatic lipase inhibitor, flavonoids from the fruit’s peel were purified by Sephadex LH-20 column chromatography and identified by high performance liquid chromatography-mass spectrometry (HPLC-MS) and Fourier transform infrared (FTIR) spectroscopy. Moreover, the type of inhibition and the molecular interaction between the flavonoids and pancreatic lipase were studied by enzymatic reaction kinetics and molecular docking. The results of purification and identification showed the major flavonoid compound in Guanxi honey pomelo was naringin. The half-maximal inhibitory concentration (IC₅₀) of naringin on pancreatic lipase was 0.99 μg/mL. The inhibition was reversible non-competitive. The inhibition constant K_i was 0.58 μg/mL. Molecular docking showed that the binding free energy between the flavonoid compound and the enzyme was −30.14 kJ/mol. They interacted with each other at a position outside the catalytic core via van der Waals force, hydrophobic interaction, hydrogen bond and π bond. This study revealed that naringin as one of the main flavonoids in Guanxi honey pomelo could strongly inhibit pancreatic lipase, which will provide a theoretical basis for the development of flavonoids from Guanxi honey pomelo as new and safe pancreatic lipase inhibitors.

In this study, our purpose was to investigate the effect of mild salting on the flavor of large yellow croaker. The volatile flavor compounds of raw (unsalted) and low-salted large yellow croaker were determined by solid phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) and evaluated by gas chromatography-olfactometry (GC-O) and odor activity values (OAV) analysis. The GC-MS analysis showed that the contents of hexanal, nonanal, heptanal, 1-octene-3-ol, anethole and hexanol in both samples were higher than those of other volatile compounds identified. GC-O and OAV analysis showed that the flavor of raw large yellow croaker was significantly affected by 1-octene-3-ol, octanal, nonanal, hexanal, heptanal, (E,Z)-2,6-nonadienal, trans-2-octenal and anethole (OAV > 1); the flavor of low-salted large yellow croaker was significantly affected by linalool, nonanal, hexanal, octanal, 1-octene-3-ol, anethole, (E,Z)-2,6-nonadienal and heptanal (OAV > 1). The changes in flavor after salting treatment was attributed to a significant increase in the OAV of linalool and anethole, and a significant decrease in the OAV of 1-octene-3-ol, hexanal, nonanal, trans-2-octenal, (E,Z)-2,6-nonadienal, heptanal and octanal. The changes of some flavor components might be related to reactions such as the oxidative degradation of unsaturated fatty acids, the biosynthesis of terpenoids, the isomerization of aromatic alcohols, the oxidation and reduction of aliphatic aldehyde and esterification.

The rational design of Aspergillus niger β-mannanase was carried out in order to obtain mutants with improved thermal stability and catalytic activity. The FireProt server was used to analyze the β-mannanase and four single-point mutants were selected. The mutant genes were obtained by site-directed mutagenesis, and the mutant enzymes were expressed and purified in vitro. The enzymatic properties of the mutants were determined using locust bean gum as the substrate, and the mutant E325M was selected on the basis of its improved thermal stability and catalytic activity of A. niger β-mannanase. Compared with the wild type (WT), the catalytic activity of E325M was increased by 33.8%. After treatment at 60 ℃ for 1 h, the residual activity of E325M was increased by 40.2%. The half-life of E325M at 60 ℃ was 72.2 min, which was 1.22 times longer than that of WT. The surface electrostatic charge analysis showed that the optimization of the surface charge of mutant E325M was beneficial to improve the thermal stability of the enzyme. Molecular docking analysis showed that the enhanced hydrogen bonding between the enzyme and the substrate may be responsible for the simultaneous improvement of the thermal stability and catalytic activity of E325M. Molecular dynamics simulation showed that the increased thermal stability and catalytic activity of mutant E325M could be attributed to the increased rigidity of some α-helix regions and the increased flexibility of the important catalytic residues D152 and E206. These findings provide a useful strategy for improving the thermal stability and activity of β-mannanase from A. niger, and promote understanding of the relationship between β-mannanase structure and function, as well as the industrial application of the enzyme.

In this study, we examined changes in the color, texture characteristics, nutrient composition and in vitro digestibility of kelp seedlings after hot water blanching. The results showed that after blanching, the L* value of kelp seedlings increased significantly, the b* and a* values decreased significantly, and the crispness, chewiness and resilience increased significantly. In addition, the contents of total sugar and fucoxanthin decreased significantly, while the contents of crude fiber and protein increased by 1.91 and 0.48 g/100 g, respectively. The in vitro intestinal digestibility of proteins in kelp seedings decreased significantly after hot water blanching, but the digestibility of fucoxanthin and total sugar increased. This study showed that hot water blanching improved the color, texture characteristics, crude fiber and protein contents of kelp seedlings, and promoted the digestion of fucoxanthin and total sugar, which provides a reference for the processing and utilization of kelp seedlings.