The nutritional components of different parts (meat, head, shell and tail) of Litopenaeus vannamei (L.v), Macrobrachium rosenbergii (M.r), Penaeus monodon (P.m), Fenneropenaeus chinensis (F.c), and Penaeus japonicus (P.j) were analyzed and their nutritional values were evaluated. For the five species of shrimp, the meat yield was 37.47–55.94%, and the byproduct yield was 44.06–62.53%. The meat yields of L.v and F.c were the highest (55.94 and 55.92%, respectively), and the meat yield of M.r was the lowest (37.47%). The shrimp contain high amounts of crude protein, and the values of the amino acid score (AAS), chemical score (CS), and essential amino index (EAAI) were greater than or close to 1.00, indicating that shrimp protein had higher nutritional value. The shrimp head was rich in polyunsaturated fatty acids and the ratio of n-6 to n-3 PUFAs was from 0.37 to 1.68, indicating that the shrimp head is rich in n-3 PUFAs and is a good source of n-3 PUFAs. The five species of shrimp were rich in macro- and micro-minerals, especially in shrimp byproducts. The shrimp byproducts were also rich in other bioactive ingredients (astaxanthin), which are also very valuable for developing biological resources. Therefore, shrimp have many nutritional benefits, and their byproducts can also be used to develop natural nutraceuticals, which are considered to be one of the healthiest foods.

Oyster, which is rich in protein and widely used as a marine traditional Chinese medicine, was believed to have good curative effects in health care and on chronic diseases. This study was designed to evaluate the anti-fatigue and anti-oxidant effects of oyster hydrolysate. Oyster meat (OM) was hydrolyzed with a complex protease, and oyster hydrolysate (OH) was separated by a 6 kDa ultrafiltration membrane into two fractions, OH-I (<6 kDa) and OH-II (≥6 kDa). The anti-fatigue effects of OM, OH, OH-I and OH-II groups were first investigated, and then the antioxidant activities of OH-I and OH-II were further analyzed. Anti-fatigue experimental results showed that OH-I displayed the strongest activity among the four groups. Compared to the control group, OH-I significantly prolonged swimming time (67.79%), increased the content of muscle glycogen (45.65%) and liver glycogen (49.01%), and reduced the content of blood urea nitrogen (BUN) (18.44%) (P < 0.05). Meanwhile, OH-I showed excellent chemical and cellular antioxidant activities, especially when the concentration increased; its antioxidant activity was significantly better than that of OH-II (P < 0.05). Results of an amino acid analysis showed that OH-I was rich in branched-chain amino acids (10.84 g per 100 g), Glu (8.63 g per 100 g), Tau (1.68 g per 100 g), Asp (5.02 g per 100 g) and Arg (3.61 g per 100 g), which were expected to contribute to its antioxidant and anti-fatigue activities.

Antarctic krill is a high-quality animal protein resource, but the presence of fluorine limits its development. Antarctic krill defluoridated hydrolysate products (DHPs) generally have a bitter taste that is unacceptable to consumers. Therefore, it is necessary to improve the flavor of defluoridated hydrolysate. In this work, flavor improvement of DHPs by the Maillard reaction was evaluated by sensory analysis, electronic nose (E-nose), and gas chromatography-mass spectrometry (GC-MS). The potential correlations among the signals of sensory attributes, E-nose, and volatile components were analyzed using the analysis of partial least squares regression (PLSR). A total of 63 volatile compounds were identified and quantified via GC-MS. The flavors in Maillard reaction products were mainly attributed to pyrazines, aldehydes, ketones, and furans. After the Maillard reaction, the two main aromatic compounds generated were 3-ethyl-2,5-dimethylpyrazin (roast odor, OAV = 32.7) and 3-(methylthio) propionaldehyde (shrimp meat odor, OAV = 16.43), which contributed to flavor improvement in DHPs. PLSR results showed a good correlation between most variables of sensory attributes, E-nose, and volatile compounds, which indicates that the overall flavor of DHPs was improved by the Maillard reaction. Abbreviations: DHPs: defluoridated hydrolysate products; MRPs: Maillard reaction products; GC-MS: gas chromatography-mass spectrometry; E-nose: electronic nose; OAV: odor activity value; SPME: solid-phase microextraction; GC-O: gas chromatography-olfactometry; PCA: principal component analysis; PLSR: partial least squares regression