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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 180–1 000 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.

In this study, the effects of different recovery methods on the structure and functional properties of sarcoplasmic proteins from silver carp surimi wash water were analyzed. The results showed that acidic pH-shifting and heat treatment had a great effect on the degree of conversion of –SH groups to disulfide bonds, surface hydrophobicity, intrinsic tryptophan fluorescence intensity, solubility and foamability of sarcoplasmic proteins. Secondary structure analysis showed that freeze drying and heat treatment gave rise to a higher relative content of β-sheet; isoelectric point precipitation, acidic pH-shifting alone and in combination with chitosan flocculation resulted in a higher relative content of random coil; chitosan flocculation led to a higher relative content of β-turn. These methods consistently yielded a lower relative content of α-helix, and caused the secondary structure of sarcoplasmic proteins to transform from an ordered to a disordered state. In addition, chitosan could bind to sarcoplasmic proteins to form large molecular mass complexes, whereas acidic pH-shifting caused partial decomposition of sarcoplasmic proteins. The structural changes cause by the different recovery methods affected the functional properties of sarcoplasmic proteins. The sarcoplasmic proteins prepared by acidic pH-shifting coupled with chitosan flocculation had much higher surface hydrophobicity and consequently poorer emulsifying properties, while those obtained by freeze drying, isoelectric point precipitation, and chitosan flocculation had stronger emulsifying properties. Notably, chitosan treatment significantly improved the emulsifying properties of sarcoplasmic proteins.

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.

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 1 034.62 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.

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 (1 403 and 1 026 cm-1) of glycoproteins gradually enhanced with increasing drying time. The response values of the electronic nose sensors W1W (sulfides) and W2S (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.