Research On Antioxidant Activity Of Fast Fermented Shrimp Paste

Shrimp paste is an aquatic seasoning with a long history, and it is very popularing in our country and Southeast Asia for its unique flavor and rich nutrition value. However,production of traditional shrimp paste needs more time, restricting the industrialization of shrimp paste. Thus, it is necessary to study fast fermentation technology; In addition,shrimp paste possessed many biological activity,such as lowering cholesterol, lowering blood pressure, beneficial bacteria, antioxidant, etc. Although there were a lot of researches about antioxidant activity, research on playing the antioxidant activity components of shrimp paste was relatively small. Therefore, in order to improve the study of shrimp paste in functional aspects, and further promote the development of traditional fermented seasoning industry, This paper by modern fermentation method, adding microorganism method fermented shrimp paste, analyzed the change rule of antioxidant activity during fermented process of shrimp paste with the detection index of DPPH radical scavenging power, hydroxyl radical scavenging power and reducing power; it also analyzed interaction among starter cultures in the antioxidant activity during shrimp paste fermented process;Finally using Capto Q-FF strong anion exchange column and ODS C18 column-coupled UPLC-Q-TOF-MS achieved separation, purification and structure identification of shrimp paste antioxidant peptide; Main results are as follows:(1) Changes of nutrient composition and antioxidant activity during fermented process of shrimp paste. Using methods of adding microorganism and simulation system of traditional fermented shrimp paste means got two kinds of shrimp paste. Comparing before and after fermenting, amino nitrogen content of the traditional fermented shrimp paste increased from 0.23 g/100 g to 0.58 g/100 g, volatile base nitrogen content increased from13.6 mg/100 g to 43.6 mg/100g; And amino nitrogen content of fast fermented shrimp paste increased from 0.38 g/100 g to 0.84 g/100 g, volatile base nitrogen content increased from17 mg/100 g to 50.1 mg/100g; and changes of protein, fat content showed that fast fermented shrimp paste could decompose the protein in a relatively short time.Meanwhile, comparing before and after fermenting, hydroxyl radical scavengingcapacity of traditional fermented shrimp paste increased from 52% to 86%, and fast fermented shrimp paste increased from 54% to 75.2%. In addition, DPPH radical scavenging ability and reducing power of two types of shrimp paste also had trend of increase.(2) Relationship analysis between protease and antioxidant activity during fermented process of shrimp paste. Shrimp paste was fermented by respectively using single bacteria, lactic acid bacteria, yeast and aspergillus niger, double bacteria lactic acid bacteria and yeast, lactic acid bacteria and aspergillus Niger, yeast and aspergillus niger,compound bacteria(lactic acid bacteria, yeast and aspergillus niger), eventually found neutral protease was main protease in single bacterium fermentation system, double bacteria fermentation system, and compound bacterium fermentation system.The analysis result of microorganisms interaction in shrimp paste system based on DPPH radical scavenging ability, showed that adding lactic acid bacteria had no effect on the yeast, but had a synergistic effect to aspergillus niger; adding yeast was no effect on lactic acid bacteria, but has a synergistic effect to aspergillus niger; And adding aspergillus niger had inhibitory effect on both lactic acid bacteria and yeast. And change rule of shrimp paste system protease enzyme activity and DPPH radical scavenging ability suggested that both of them are related.(3) Separation and identification of antioxidant peptide from fast fermented shrimp paste. Six components(P1 to P6) were isolated from shrimp paste water extraction liquid by the Capto Q FF strong anion exchange column, which found peak5(P5) had high ABTS radical scavenging ability; Analyzing the active component by UPLC-Q-TOF-MS after further purification with reversed phase column ODS C18, preliminary identificated result was dipeptide Trp-Pro by mass spectrometry, the molecular weight m/z301.1 Da.