Isolation, Screening And Application Of Lactic Acid Bacteria From Fermented Fish Products

Fermented fish products were fermented with fish, rice powder and other materials in anaerobic condition. As a traditional food, fermented fish products have the characteristic of abundant nutrition, special flavor and good taste, which were favored by the costumer of Southeast Asia and South of China. However, fermented fish products chiefly were produced by the process in manual workshop. The technical of products had no systematic studies. In order to realize the industrial production of fermented fish products, effects of adding amount of material and fermentation condition on the quality of fermented fish were studied by the solid-state fermentation, and predominant lactic acid bacteria such as Pediococcus pentosaceus and Lactobacillus plantarum were separated from fermented fish products in optimum condition. Using the mixture of P. pentosaceus and L. plantarum as starter, changes of microbiological, physico-chemical and sensory indexes of inoculated fermented fish products were compared with those of natural fermented fish products. The results were as follows:(1) Technics of natural fermented fish products were optimized. Quality of fermented fish products obviously correlated to the adding amount of rice powder, salt, water and pimiento, fermentation temperature and fermentation time, especially correlated to the adding amount of rice powder and salt, fermentation temperature and fermentation time. Fermented fish products with optimum flavor and taste were obtained when fermented with 100 g fish, 45 g rice powder, 2 g salt and proper supplementary materials under anaerobic environment at 25℃for 60 h whose pH, content of titratable acidity, water-soluble solid, water-soluble protein and free amino acid of fermented fish products were 4.18, 1.01% ,7.02%, 28.40 mg/g and 9.62 mg/g, respectively.(2) Lactic acid bacteria were separated and identified from fermented fish products. 5 predominant colonies lactic acid bacteria, serial number 3, 19, 22, 46 and 55 were separated from natural fermented fish products. All of the five lactic acid bacteria were of homofermentation, not producing gas and mucus but producing acid, growing in the condition of 6.0% salt. By experiments of biochemistry and sugar fermentation, 3 colonies lactic acid bacteria (serial number 3, 19 and 55) were proved to be P. pentosaceus, and the other 2 colonies lactic acid bacteria (serial number 22 and 46) were L. plantarum. All of the five lactic acid bacteria could grow under the condition of 20℃～45℃. P. pentosaceus (Serial number 3) and L. plantarum (Serial number 46) had better ability of acid production and growth in the condition of 6.0% salt than others.(3) The Preparation of starter culture and fermenting capability were studied. Using P. pentosaceus (Serial number 3) or L. plantarum (Serial number 46) as the starter, the optimum inoculating dosage was 10~7 cfu/100 g or 10~8 cfu/100 g. Using mixture of P. pentosaceus and L. plantarum as the starter, optimum proportion of P. pentosaceus and L. plantarum was 1∶10 and inoculating dosage were 10~7 cfu/100 g and 10~8 cfu/100 g, respectively. Fermented fish products with the starter had better ability of acid production and quality of production than those of single lactic acid bacteria as starter.(4) Using the mixture of P. pentosaceus and L. plantarum as starter, changes of microbiological, physico-chemical and sensory indexes of natural and inoculated fermented fish products were studied. During the fermentation, pH, content of titratable acidity, water-solube solid, soluble protein and free amino acid of natural fermented fish products were remarkably different from those of inoculated fermented fish products. When fish products were fermented with the starter, the amount of lactic acid bacteria, rate of acid production, pH, content of water-soluble protein, water-soluble solid and free amino acid were obvious better than those of natural fermented fish products. Compared to natural fermented fish products on sensory indexes, the taste of inoculated fermented fish products was better.