Preparation of Crayfish(Procambarus clarkia)Head Paste by Microbial Composite Fermentation and Its Umami Substances Analysis

In the paper,Staphylococcus xylosus,Pediococcus pentosaceus and Saccharomyces rouxii were added as mixed fermentation strain. Based on the sensory evaluation value and amino nitrogen content,the mixing ratios of the 3 kinds of microorganisms were investigated,and the conditions of crayfish head pasta fermented by mixed strains were explored by single-factor tests and response surface methodology. The results showed that the optimal mixing ratio of Staphylococcus xylosus,Pediococcus pentosaceus and Saccharomyces rouxii was 1:3:3.The optimum autolysis condition was extracted based on the equation:Fermentation time 22.3 h,fermentation temperature 33.49 ℃,inoculation quantity 40.11 mL/kg. Under the above optimum fermentation conditions,the sensory evaluation value was 7.55 scores,and the content of amino nitrogen was(6.58±0.08) mg/mL.The umami substances of crayfish head hydrolysate before and after fermentation were analyzed by physicochemical indexs. The results showed that after fermentation,the content of taste amino acids changed little(p>0.05);the content of free amino acids was 8605.45 mg/kg,increased by 5.4%;the glycine(Gly)content of taste amino acids was 589.49 mg/kg,increased by 24.03%. The content of nucleotide related compounds before and after fermentation changed little(p>0.05). After fermentation,the content of inosine monophosphate(IMP)and guanosine monophosphate(GMP)was 3.39(increased by 31.5%)and 34.16 mg/kg respectively,which greatly contributed to toumami flavor. Crayfish head paste,prepared by microbial composite fermentation,was nutritious,full of flavor with unique and harmonious taste,and could be used as better basic material for condiment.