Seperation Of Flavor Microorganisms In Traditonal Shrimp Paste And Research On Fast Fermentation Technology

Shrimp paste is a common aquatic seasoning of coastal areas and southeast Asia,traditional shrimp paste has unique flavor and rich nutrition, but it is difficult to realize theindustrialization development because of old technology, high salinity and qualityinstability. In order to promote the development of shrimp paste industrialization, andenhance productivity, shrimp paste fast fermentation technology was studied with modernbiological technology in this paper.The flavor dominant microorganisms were isolated from traditional Chinese shrimppaste with the method of dilution plating, screening and identification; The effect offermentation temperature, fermentation time and inoculation quantity of starter culturewere studied with response surface analysis; Shrimp paste flavor composition of differentphases were determined by use the sensory evaluation, automatic amino acid analyzer,electronic nose, SPME-GC-MS and determination of physical and chemical indicators. Themajor results are as follows:(1) There was not meet the requirements for the fermentation of Lactobacillus spp.and Staphylococcus spp. isolated from traditional Chinese shrimp paste; Anaroma-producing yeast was isolated from traditional Chinese shrimp paste with the methodof aroma sensory analysis. The routine identification and ITS rDNA analysis showed that itbelonged to Pichia gilliermondii. The salt-tolerance analysis indicated that the strain cansurvive under10%NaCl. The results showed that the aroma-producing ability and salttolerance of strain were good, and it can be used for low-salt shrimp paste fermentation. Aproducing protease mold isolated from traditional Chinese shrimp paste, by ITS rDNAsequence analysis, and combining with morphological identification of the fungi belongingto the Aspergillus niger. Acid protease activity, neutral protease activity and alkalineprotease activity was825.7U/mL,32.6U/mL,2.6U/mL, respectively. The results showedthat acid protease activity is higher, neutral and alkaline protease activity is low, it canthrough the optimization of fermentation conditions to improve the enzyme activity.(2) Optimization of fast fermentation process. In order to improve the flavor andtexture of shrimp paste, shrimp heads are fermented by Lactobacillus planticola, Pichiagilliermondii and Aspergillus niger.The optimal conditions were defined as follows: the ratio of Lactobacillus planticola, Pichia gilliermondii and Aspergillus niger is1:5:3,fermentation temperature,53.6℃; fermentation time,13.46d; inoculationquantity ofstarter culture,2.69%by response surface analysis.(3) The major flavor compounds of free amino acid, volatile flavor compounds indifferent stages of shrimp paste were quantified with the sensory evaluation, automaticamino acid analyzer and SPME-GC-MS. The results showed: after fermentation theamount of free amino acid of fast fermentation shrimp paste from2320mg/100mLincreased to5640mg/100mL; The free amino acid of traditional fermentation shrimp pastefrom2590mg/100mL increased to7826mg/100mL.Rapid fermented shrimp paste, traditional shrimp paste and commercial shrimp pasteanalyzed by electronic nose, the results showed that the traditional shrimp paste wholesmell is most close to commercial shrimp paste, there is a certain difference between fastfermented shrimp paste and commercial shrimp paste smell.Volatile compounds were analyzed by SPME-GC-MS, a total of60and53kinds ofvolatile compounds were separately identified in the fast fermentation shrimp paste andtraditional shrimp paste. Fast fermentation shrimp paste was more volatile compounds. Thevolatile compounds of fast fermentation shrimp paste were most of aldehydes, ketones,pyrazine and sulfuric compounds. The volatile compounds of traditional shrimp paste weremost of aldehydes, hydrocarbon and pyrazine. Compare the determination results withcommercially available shrimp paste, the results indicated pyrazines were the primaryconstituents of shrimp paste flavor.The determination of physical and chemical indicators. The result showed: comparewith traditional shrimp past, the fast fermentation shrimp paste more advantage. Thechange of protein content, amino nitrogen content, total acid content, total volatile basenitrogen(TVB-N) content in different phases of shrimp paste fermentation indicated thatprotein hydrolyzed and flavor compounds produced in a relatively short time in fastfermentation, it is advantage to enhance productivity and control the quality of shrimppaste. In addition, the advantage of low salt of fast fermentation can promote to shorten theprocess of fermentation.In conclusion, the low-salt fermented shrimp paste produced by fast fermentation,although the flavor of fast fermentation shrimp paste is slightly different from traditionalshrimp paste, but it still had advantages of low salt, fermentation time shortly, and qualitystability.