The patterns of changes in the physicochemical properties and volatile flavors of abalone muscle during drying at 50 ℃ and 65% relative humidity were investigated in this study. With an increase in drying time, the browning intensity and fluorescence intensity of both surface and internal muscles of abalone increased gradually, which started to decrease after reaching a peak on the 90th day. The contents of reducing sugar and lysine in the surface muscle were 3.11 mg/g and 2.60% after pretreatment, and decreased to 1.95 mg/g and 1.61% after 120 days of drying, respectively. High molecular mass polymers were observed in the electrophoretic pattern of abalone muscle after 30 days of drying. Fourier transform infrared spectra showed that the intensity of the characteristic absorption peaks (1403 and 1026 cm^-1) of glycoproteins gradually enhanced with increasing drying time. The response values of the electronic nose sensors W1W (sulfides) andW2S (alcohols, aldehydes and ketones) increased, and the content of 1-octen-3-ol decreased while the contents of linalool and (E,E)-2,4-decadienal increased after 30 days of drying, as determined by gas chromatography-mass spectrometry (GC-MS). At the same drying time, the intensity of Maillard reaction in the surface muscle was weaker than that in the internal muscle.

During oven drying of abalone muscle, microwave treatment was conducted at regular time intervals (0, 30, 60, 90 and 120 days). Abalone muscle digestion products (AMDP) were prepared by subjecting dried abalone to in vitro simulated digestion. Our aim was to investigate the effect of microwave treatment during the drying of abalone muscle on the in vitro and in vivo antioxidant activities of AMDP. The results showed that the half maximal inhibitory concentration (IC₅₀) values of AMDP from fresh abalone muscle for scavenging capacity against hydroxyl (·OH) radicals, N,N-dimethyl-p-phenylenediamine dihydrochloride (DMPD) and 1,1-diphenyl-2-phenylhydrazine (DPPH) radical were 3.04, 15.18 and 21.12 mg/mL, respectively. The IC₅₀ values for the scavenging of these three radical species decreased gradually with increasing the drying time of abalone muscle. After being fed AMDP from abalone muscle dried for 120 days, the body length of Caenorhabditis elegans increased from 768.90 to 1034.62 μm, the head swing frequency increased from 206 to 281 times/min, and the life span was extended by 36.16% under normal conditions and by 59.41% and 38.48% under heat stress and oxidative stress conditions, respectively compared with the control group. Meanwhile, with prolonging the drying time of abalone muscle, the antioxidant enzyme activities, reduced glutathione (GSH) content and total antioxidant capacity of C. elegans fed AMDP increased, and the reactive oxygen species (ROS) content decreased. In summary, prolonging the drying time and using microwave treatment during the drying process could improve the antioxidant capacity of AMDP.

In order to explore the interaction between lipid and protein in film-forming solutions and films, the effects of linoleic acid concentration (0%, 10%, 20%, 30% and 40% relative to protein mass) on the viscosity of 11S globulin film-forming solutions, and the microstructure and physicochemical properties of the resulting films were studied. Confocal laser scanning microscopic (CLSM) images showed that the size of oil droplets in the film-forming solution increased with increasing linoleic acid concentration, and it further increased after drying. According to the results of scanning electron microscopy (SEM), oil droplets accumulated on the upper surface of the smooth and dense protein films after adding linoleic acid, while the lower surface became rough without accumulation of oil droplets on it. After adding 40% linoleic acid, the glass transition temperature, tensile strength and water vapor permeability of the film decreased from 53.50 ℃, 12.67 MPa and 2.52 × 10^-10 g/(m·Pa·s) to 50.38 ℃, 7.30 MPa and 1.83 × 10^-10 g/(m·Pa·s), respectively, while the elongation at break increased from 95.58% to 198.15%. Molecular dynamics simulation showed that 11S globulin did not interact with linoleic acid below 200 ns. The proportion of ionic bonds and disulfide bonds in the 11S globulin film decreased with the addition of linoleic acid, while the proportion of hydrophobic interactions and non-disulfide covalent bonds increased. These results suggest that the addition of linoleic acid can change the chemical interactions among proteins, thus affecting the physicochemical properties of the film. This finding provides a theoretical reference for studying the mechanism of film formation of soybean protein emulsion films.

In this study, the effect of shrimp oil-based simulated fat on the flavor and physical properties of shrimp (Litopenaeus vannamei) surimi products was investigated. The sensory evaluation results showed that the smell and taste scores of surimi products increased with the increase in simulated fat content. By gas chromatography-ion mobility spectrometry (GC-IMS), a total of 30 volatile organic compounds were identified in shrimp surimi products with simulated fat, and the contents of ketones and esters increased with the increase in simulated fat content. The highest hardness and gel strength of 2472.04 g and 826.14 g·mm, respectively were obtained when the simulated fat content was 4.0%. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) showed that when added at 4.0%, the simulated fat was evenly distributed in the dense gel network of surimi products. Therefore, adding an appropriate amount of shrimp oil-based simulated fat can not only enhance the sweet flavor of shrimp surimi products, but also improve its gel properties. The results of this study can provide a theoretical basis for the quality improvement of shrimp surimi products.

To explore anti-aging and antioxidant activities of Phyllophorus proteus hydrolysate fraction (PPHF) on Caenorhabditis elegans, the physiological and biochemical indicators of C. elegans fed 0.5, 2.0 mg/mL and 8.0 mg/mL PPHF were determined. The results showed that PPHF was beige in color, and its L^* and b^* values were 81.28 and 15.88, respectively. The proportion of oligopeptides with molecular mass of 180–1000 Da in PPHF was 63.76%, and the proportions of glutamic acid and glycine were 19.50% and 15.34%, respectively. After being fed 0.5, 2.0, and 8.0 mg/mL PPHF, the lifespan of C. elegans was increased by 22.43%, 54.60%, and 78.89%, respectively, under normal conditions, and also increased under thermal or oxidative stress. The body length of C. elegans was increased significantly by feeding 0.5 mg/mL PPHF, while the swallowing frequency was significantly increased by feeding 2.0 mg/mL PPHF. The body bending frequency of C. elegans fed 0.5 and 8.0 mg/mL PPHF was increased by 7.75% and 43.71%, respectively, when compared with the control group on the second day of incubation. PPHF significantly reduced the content of reactive oxygen species (ROS) in C. elegans, and increased the antioxidant enzyme activity, glutathione content and total antioxidant capacity in a dose-dependent manner. These results indicated that PPHF could improve the physiological function and prolong the lifespan by enhancing antioxidant capacity in C. elegans.

A water-soluble polysaccharide from abalone muscle (AMPP) was isolated. The contents of carbohydrate, protein, uronic acid, and sulfate in AMPP were 83.5%, 0.5%, 2.7%, and 2.6%, respectively. High-performance liquid chromatography analysis indicated that AMPP was homogeneous and had an average molecular weight of approximately 3.2 kDa. The main monosaccharides of AMPP were glucose (Glc) and mannose with a molar ratio of 99.7:0.3. The structural characteristics of AMPP were elucidated through methylation analysis, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The linkages of AMPP consisted of terminal, 1,4-linked, 1,6-linked, and 1,4,6-linked Glcp with a molar ratio of 3.1:7.2:1.0:2.5. In one repeat unit of the proposed AMPP structure, the backbone chain was composed of eight 1→4 glycosidic bonds and one 1→6 glycosidic bond, with three branch chains linked by 1→6 glycosidic bond. In addition, AMPP was found to possess potent immunostimulatory activity via rising phagocytosis of RAW264.7 cells and promoting secretion of TNF-α.