No abstract

Microalgae protein hydrolysates (MPH) were obtained by enzymatic hydrolysis of defatted microalgae meal using neutral protease. The protein recovery, degree of hydrolysis, and the antioxidant activities of the hydrolysates were investigated. The results demonstrated that hydrolysates prepared by neutral protease at 50 °C for 4 h exhibited the strongest antioxidant activity. Under these conditions, the 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical scavenging activity and the reducing power of the hydrolysates were 68.3%, 50.8% and 1.303, respectively.

Lactic acid bacteria commonly used in fermented meat products, dairy products and smoked products such as pickled food industry. They can make the products have a special flavor and color, inhibit the growth of pathogenic bacteria, and reduce the nitrite content of products, improve food security. 12 strains of lactic acid bacteria were isolated from the salted fish. Some of their biochemical characteristics were studied and compared, as well as their abilities on the tolerance and degradation of nitrite. 3 strains named b2、j2、j5 were approved to degrade nitrite quickly with good biochemical characteristics. After amplification and sequencing of 16S rDNA gene, the isolated strains were identified by sequence homology as Lactobacillus plantarum, Leuconostoc mesenteroides and Pediococcus pentosaceus. Strainb2, j2 and j5could degrade 96.2%, 85.6%, 91.2%.

Ultrasonic-freeze-thaw-cycle assisted extraction was used to synchronously extract polysaccharide and phycobiliprotein from Gracilaria lemaneiformis. Firstly, different solvents (deionized water, sodium hydroxide, phosphate buffer solution (PBS) and calcium chloride solution) were screened, and PBS (1 mM, pH 6.8) was considered as the best solvent for its OD565 value (0.086±0.0003) and OD595 value (0.471±0.002), which was significantly higher than any other solvents (p<0.05). Moreover, an L9 (3)4 orthogonal test was carried out to optimize extraction conditions, based on the single-factor test. The results indicated that the optimized conditions were fixed as follows: the ratio of solid to liquid 1:25 (w/v), 2 times of freeze-thaw cycles, ultrasound power 320 W and ultrasound time 10 min, which obtained the optimum yield and purity of polysaccharide and phycobiliprotein, 30.54%, 1.36% and 0.296, respectively. As a result, ultrasonic-freeze-thaw-cycle assisted extraction is considered to be an effective, economic and eco-environmental method to extract polysaccharide and phycobiliprotein.