DPA showed an anti-inflammatory profile by competing with AA to decrease the synthesis of pro-inflammatory eicosanoids (LTB₄and PGE₂).

Bacterial growth and histamine formation in mackerel during storage at 0, 4, 15 and 25C were monitored. Histamine production and bacterial multiplication were accelerated with increase of the storage temperature. The highest histamine level of 2,080 mg/kg was detected after 2 days of storage at 25C. Selective media were used for isolation of histamine-producing bacteria (HPB) and the histamine production was confirmed by high-performance liquid chromatography analysis. A total number of 305 strains were isolated from spoiled mackerel and 32 of them were identified as HPB. Most of the HPB were isolated from violet red bile glucose agar. Morganella morganii, Citrobacter braakii, Hafnia alvei and Raoultella planticola were confirmed as high histamine-producing strains, whereas other microorganisms were found to possess weak histamine-producing ability. Practical Applications In order to effectively inhibit the activity of HPB, it is necessary to have a good understanding of bacterial species contributing to histamine production in mackerel during storage. Therefore, we studied the variation of histamine content and the growth of bacteria related to histamine production in mackerel during storage. Results of this study could be useful to assure the safety of mackerel products by controlling histamine content.

N-3 polyunsaturated fatty acids (n-3PUFA) are regarded as viable alternatives to aid the treatment of ulcerative colitis (UC). Most research focuses on eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA); little information is available about the effect of docosapentaenoic acid (DPA) on the gut microbiota and their metabolism in UC mice. In this study, the changes in gut microbiota and their metabolism in UC mice were studied through the 16S rRNA sequencing method and untargeted metabolomics. Moreover, the differential bacterial genus and differential metabolites in responding to DPA supplementation were screened through permutation test after orthogonal partial least squares discriminant analysis (OPLS-DA). The results indicated that DPA supplementation increased the diversity and altered the composition of the gut microbiota in UC mice; Akkermansia, Alistipes, Butyricicoccus, and Lactobacillus were selected as the differential bacterial genus. Supplementation of DPA also altered the fecal metabolite profile in the UC mice. Moreover, butyrate, N-carbamylglutamate (NCG), and histamine were screened as the differential metabolites. In conclusion, the regulation effect of DPA on the gut microbiota and their metabolism might be involved in the intervention mechanism of DPA in UC. More research needs to be carried out to elucidate the mechanism systematically.

Making Antarctic krill oil into emulsion is a good way to utilize Antarctic krill, but proliferation of microorganisms cannot be ignored. H₂O₂ is widely used in the sterilization of liquid food since its decomposition products are environmentally friendly, although residual H₂O₂ should be removed for food safety. Adding catalase (CAT) is an effective means to do this. However, the enzyme activity center of CAT is the iron porphyrin group, which has the risk of accelerating lipid oxidation in the oil emulsion. Therefore, we hypothesized that CAT might not be suitable for the removal of H₂O₂ in Antarctic krill oil emulsion. In this paper, Antarctic krill oil emulsion was prepared, and then the effect of CAT on the emulsion was studied through visual observation, microscopic morphology observation, turbidity and stability, particle size, and ζ-potential; finally, the mechanism of CAT destroying the emulsion was explored from the perspective of lipid oxidation. The results showed that a stable Antarctic krill emulsion was prepared using Tween-80 as the emulsifier, with the oil concentration of 1% (v/v) and the ratio of surfactant to oil phase of 1:5 (v/v). The emulsion treated with CAT had undergone demulsification, stratification, and coagulation after 2 days of incubation, while the emulsion treated with superoxide dismutase (SOD) and bovine serum albumin (BSA) changed little. In addition, the thiobarbituric acid reactive substances (TBARS) value and the content of hydroxyl radicals in the CAT group increased significantly. The preliminary research results indicated that the effect of CAT on the emulsion related to the lipid oxidation caused by the iron porphyrin group at the center of the enzyme activity. All these results indicated that CAT was not suitable for the removal of residual H₂O₂ in Antarctic krill oil emulsion. Moreover, it is helpful to avoid the contact of Antarctic krill oil emulsion and CAT during the processing of the krill.