The basic nutritional and major functional components of the lyophilized powder of Apostiopsis japonicus gonads were determined. The effects of Apostiopsis japonicus gonads on immune function in mice were also investigated. Results showed that both the female and male gonads were rich in nutrients and functional components. The protein content of the male gonad was as high as 74.54 g/100 g, which was significantly higher than that of the body wall of Apostiopsis japonicus (P < 0.05). The polysaccharide content of the female gonad was comparable to that of the body wall. The saponin content was as high as 4.77 g/100 g, which was more than ten times higher than that of the body wall. Compared with the control group, feeding Apostiopsis japonicus gonads could significantly increase the thymus and spleen indices of mice and improve the activity of natural killer (NK) cell. In the mice fed with the male gonad, the NK cell activity increased to (47.19 ± 4.99)%, the serum level of interleukin-6 (IL-6) was (209.75 ± 24.82) pg/mL, the activities of lactate dehydrogenase (LDH) and superoxide dismutase (SOD) in serum and liver increased, and the content of malondialdehyde (MDA) in liver decreased to (1.98 ± 0.25) nmol/mg. In conclusion, feeding Apostiopsis japonicus gonads could improve immune function in mice, and the effect of the male gonad was more pronounced.

Oligosaccharides are linear or branched carbohydrate compounds composed of two to ten monosaccharide residues connected by glycosidic bonds. They have many health benefits, and can function as sweeteners. Oligosaccharides are a combination of nutritiousness, health care, and dietetic therapy. Compared with polysaccharides, oligosaccharides have several advantages, such as stronger biological activity and easier absorption by the body. In recent years, marinederived oligosaccharides have been proven to have a variety of biological activities, such as antioxidant, anti-tumor, antiinflammatory, antibacterial, anticoagulant, and immunity-enhancing activities. They can be widely used in food, medicine, cosmetics, agriculture, aquatic products, and other fields. This paper introduces four major marine-derived oligosaccharides, including N-acetyl chitooligosaccharide/chitooligosaccharide, alginate oligosaccharides, agarooligosaccharides, and carrageenan oligosaccharides, and presents a brief description of their sources, structural characteristics, various biological activities and applications. It is expected to provide a reference for the high-value utilization of marine polysaccharide resources and the in-depth development of marine oligosaccharides.

In order to explore the mechanism of flavor differences, the effect of two cooking methods, namely steaming and microwaving on the lipid composition, the degree of lipid oxidation and hydrolysis, and volatile substances in Penaeus vannamei was studied. The results showed that the contents of total lipids as well as phospholipids, triglycerides, and free fatty acids in P. vannamei were significantly reduced after cooking (P < 0.05). The lipid composition differed between steamed and microwaved shrimp. Microwaved shrimp had higher phospholipid contents but lower free fatty acid contents than the steamed one. The content of saturated fatty acids decreased markedly whereas the content of unsaturated fatty acids increased significantly after cooking (P < 0.05), which may be related to the hydrolysis of phospholipids. Steaming and microwave heating accelerated the oxidation and hydrolysis of lipids, resulting in a significant increase in acid value and thiobarbituric acid reactive substances (TBARS) value (P < 0.05). The results of electronic nose analysis showed that the odor characteristics of fresh, steamed and microwaved shrimp were significantly different, and the odor of fresh shrimp changed more after microwave heating. Twenty-five volatile substances were isolated and identified from shrimp meat using gas chromatography-ion mobility spectrometry (GC-IMS). Among these compounds, 2,3-glutaraldehyde, 2-butanone, 2-methyl butyraldehyde, hexanal, 1-octen-3-one and glutaraldehyde were the major flavor substances in cooked shrimp meat and their contents were higher in the microwaved sample. Pearson correlation analysis showed that oxidative hydrolysis of lipids made an essential contribution to the flavor formation of cooked shrimp and the free fatty acids C_14:0, C_15:0, C_16:1, C_18:1n9c, C_18:2n6c and C_18:3n3 were closely related to the formation of the characteristic odors of shrimp meat.

In order to determine the optimal method for drying Apostichopus japonicus gonads, the effects of four drying methods, namely, hot air drying, cold air drying, microwave drying and vacuum freezing drying, on the lipid composition, lipid stability and fatty acid nutritional value of A. japonicus gonads were analyzed and compared. The results showed that the contents of total lipids, phospholipids, triglycerides and astaxanthin reduced to different degrees after drying treatments. The peroxide value (POV) significantly reduced, and the thiobarbituric acid reactive substances (TBARS) value significantly increased (P < 0.05). In terms of fatty acid nutritional values, the atherogenic and thrombogenic indices decreased to different degrees after drying treatments, and the hypocholesterolemic/hypercholesterolemic indices increased significantly (P < 0.05). The results of electronic nose analysis showed significant differences in odor characteristics among dried samples obtained using different drying methods. Gas chromatography-ion mobility spectrometry (GC-IMS) identified 28 volatile substances from fresh and dried samples, among which, 2,5-dimethyl pyrazine was detected only in microwavedried samples, while pentanal and ethyl acetate were odor-active substances unique to cold air-dried samples. In conclusion, vacuum freeze drying effectively slowed down the rate of lipid oxidation, but the samples were relatively bland in odor. Hot air, cold air and microwave drying all promoted lipid oxidation, but improved the nutritional value of fatty acids and enriched the odor characteristics of the samples. The results of this study could provide a theoretical basis for the processing and utilization of A. japonicus gonads.