|
This paper studied the preparation of direct vat starter (DVS) from 3 natural Lactobacillus bacteria Lactobacillus brevis, Lactobacillus casei, Lactobacillus plantarum, for using in vegetable fermentation. The effects of the 3 bacteria as starters individually or combined on the quality of cabbage pickle were investigated. pickle was fermented at room temperature (24℃) for 3 days, with following parameters monitored:pH, titratable acidity(TA), nitrite content, viable cell counts and sensory attributes. Results showed that the combination of Lactobacillus brevis and Lactobacillus plantarum at a ratio of 1:1, with a 2-3% total inoculation had the best effect on fermentation. With the above strains combination and 2% inoculation, the pH reached 3.35, TA reached 0.74%, viable cell counts was 8.93*107cfu/mL, score of sensory analysis was 12.1/15, content of nitrite was 14.2 mg/kg after 3 days of fermentation.Moreover, The high dense cultivation of L.b and L.p was studied. The period between lag phase and decline phase was 24h for L.b, the cultivation of L.b was positively impacted by a higher initial pH, and not affected by the quantity of inoculation. While the period between lag phase and decline phase was 27h for L.p. The cultivation of L.p was better at a controlled quantity of inoculation, but not much influenced by the initial pH. L.b has a better toleration to low temperature than L.p. The dense of L.b and L.p were 1.15*1010to 1.26*1010 cfu/mL by optimization.Finally, the preparation process of DVS was tried out. L.b and L.p were centrifuged at 4000rpm for 30 min, added skim milk, lactose, glucose, VC, D-sorbite, L-glutamic acid with certain ration as protect agent, and freeze-dried. The recovery of L.b and L.p by centrifuging were 63.9% and 74.6%, the yield were 3.75% and 3.50%, recovery of L.b and L.p by freeze-drying were 52.8% and 29.4%, yield were 26.9% and 23.0%. The viable lactobaccilus of DVS were 2.4*109 cfu/g and 2.74*109 cfu/g respectively. The DVS of L.b and L.p were mixed at a ratio of 1:1. It was recommended to inoculate the mixture with 1% at room temperature (24℃) for best quality of pickle fermentation. The fermented pickle had a pH at 3.5,0.89% TA,8.98*107cfu/mL viable lactobaccilus, sensory assessment score at 11.6/15.0, and the lowest nitrite content of 15.6mg/kg (far below the GB upper limit at 40mg/kg).
|