Characterisation and utilisation of microbes in the production of fish sauce and paste

[摘要] ENGLISH ABSTRACT:Fermented fish products are popular food products mainly consumed andproduced in Southeast Asia. These products are not produced in South Africa,and those available to the public are imported. The main action during theproduction and fermentation of this sort of product, is that of proteolysis, either bythe bacteria or enzymes naturally present in the fish.The prevalent microbes present in six fermented fish samples fromBangkok (Thailand) and seven from Khon Kaen (Thailand), were determined, andusing numerical methods, clustered into similarity groups using the calculateddendrogram .distance (Do) technique to determine their relation to referencestrains. Forty-seven different bacterial strains were isolated, but no yeasts,moulds or lactic acid bacteria were found. Five Gram-negative, oxidase-positivespecies, five different Staphylococcus species and nine differentendospore-forming species of the genus Bacillus, were isolated and identifiedusing the API systems. The data indicated that members of the genus Bacilluswere the prevalent organisms in all the products examined.The isolates were also scanned for general enzyme activity using the APIZym technology, and the production of proteases was investigated using theStandard Methods Caseinate and the Universal Protease Substrate methods. Itwas found that most of the isolated organisms produced protease, which is ofmajor importance in the production of fermented fish products.Proteolytic cultures from the fermented fish products, as well as lactic acidstarters, were used in the production of a fermented fresh water fish product.Production parameters including: glucose, inoculum, moisture content andincubation time, were evaluated in order to select optimum fermentationconditions. Fermentation efficiency was determined by measuring the final pH,titratable acid and the free amino nitrogen content. Optimum efficiency wasobtained with 5% (w/w) added glucose at a moisture level of 150 ml water per 100g fish.A factorial design (3 x 3 x 3) was used to indicate viable trends to facilitateoptimisation of the fermentation process. The main effects, two-factor andthree-factor interactions were calculated. Optimum trends obtained were a glucose concentration of 5% (wlw) , inoculum concentration of1x10⁸ kve.ml ̄ ¹, anincubation period of 15 days and temperature of 30°C. Three lactic acid starters(226 - Lactobacillus plantarum, 140 - Lactococcus diacetylactis and 407 -Pediococcus cerevisiae) were selected as they produced some of the bestfermentation results and are safe to use in food. It was found that a combinationof all three strains (226, 140 and 407) yielded the best results.By using the above parameters, an acceptable product was produced in terms ofconsistency, colour and aroma. Further studies need to be conducted to optimisethe safety of the product as well as the flavour, both chemically and sensoricallyoptimisation of the product.

[发布机构] Stellenbosch University