Optimized extraction of astaxanthin from shrimp shells treated by biological enzyme and its separation and purification using macroporous resin.

The best enzymatic protease treatment of shrimp shells was identified by comparing the enzymatic hydrolysis effects of many different types of biological enzymes using fresh Arctic sweet shrimp as raw materials. The optimal enzymolysis conditions were determined using neutral protease as the best enzymatic protease. Among multiple macroporous adsorption resins, XDA-8 macroporous adsorption resin was preferable due to its static adsorption rate and desorption rate. The yield of astaxanthin (134.20 µg/g) after treatment with neutral protease was 3.7 times higher than that of the control group (36.03 µg/g). The yield of astaxanthin was obviously improved after enzymolysis of the shrimp shells. The purity of the astaxanthin was up to 87.34%, approximately 6508 times higher than that of the raw material. The production cost of astaxanthin would be greatly reduced by use of XDA-8 resin to obtain high-purity astaxanthin. This technique offers a high value-added utilization of shrimp shells.

Effect of ε-polylysine and ice storage on microbiota composition and quality of Pacific white shrimp (Litopenaeus vannamei) stored at 0 °C.

This study evaluated the effects of ε-Polylysine and ice storage on microbiota composition and quality attributes of Pacific white shrimp stored at 0 °C. The sensorial shelf-life of control, 0.1% ε-Polylysine treated group, and ice stored group were 5, 8, and 7 days, respectively. Microbiota composition was explored by the Illumina-MiSeq high throughput sequencing targeting of 16S rRNA genes. At the time of sensory rejection, Pseudoalteromonas, followed by Candidatus Bacilloplama and Psychromonas, were the dominant microbiota in spoiled control samples on day 5. However, 0.1% ε-Polylysine inhibited the growth of Pseudoalteromonas and Psychromonas. Consequently, Candidatus Bacilloplama followed by Aliivibrio became the dominant microbiota in the ε-Polylysine treated group on day 8. Meanwhile, Aliivibrio, followed by Moritella and Pseudoalteromonas were the dominant microbiota in ice stored samples on day 7. Furthermore, due to the modulating effect of ε-Polylysine and ice storage on microbiota, chemical changes of the treated groups were slower, which was reflected as lower concentrations of total volatile basic nitrogen, putrescine, cadaverine, and hypoxanthine, and higher contents of inosine 5'-monophosphate and hypoxanthine riboside at the end of storage. In conclusion, ε-Polylysine and ice storage altered the microbiota composition and delayed quality deterioration of Pacific white shrimp.

Changes in Quality and Microbial Succession of Lightly Salted and Sugar-Salted Blunt Snout Bream ( Megalobrama amblycephala) Fillets Stored at 4°C.

The effect of a low concentration of salt and sugar on the quality and microbial succession in blunt snout bream ( Megalobrama amblycephala) fillets was assessed by sensory analysis, total volatile basic nitrogen, biogenic amines, K value, total viable counts, 16S rRNA gene analysis, and Illumina MiSeq PE300 high-throughput sequencing. Fish samples were left untreated (control), treated with 1.8% salt (T1), or treated with 1.8% salt plus 0.9% sugar (T2). Consequently, salted and sugar-salted treatments extended the shelf life of bream fillets by 2 days, which retarded the increase of total volatile basic nitrogen, putrescine, cadaverine, and total viable counts. The putrescine and cadaverine concentrations of T2 were significantly ( P < 0.05) higher than T1 after day 10. Brachybacterium was the major initial microbiota of bream fillets. As storage time progressed, Pseudomonas and Shewanella were major genera in the spoiled control group. Pseudomonas, Shewanella, and Pseudoalteromonas became the main spoilers in the T1 and T2 groups.