Production of Set-type Yogurt Fortified with Peptides and ¥�-aminobutyric acid by Mixed Fermentation Using Bacillus subtilis and Lactococcus lactis
2014
Lim, J.S., Keimyung University, Daegu, Republic of Korea | Lee, S.P., Keimyung University, Daegu, Republic of Korea
Mixed fermentation of cow milk was performed by sequential co-cultures with Bacillus subtilis and Lactococcus lactis. After a first fermentation step with B. subtilis for 6 h, the number of viable cells increased to 2.5¡¿108 CFU/mL. The second fermentation step with L. lactis resulted in increased viable cells 1.09¡¿1010 CFU/mL for 3 days and increased acidity. However, the number of viable B. subtilis cells was decreased greatly to 5¡¿101 CFU/mL following fermentation with L. lactis. Milk proteins were markedly hydrolyzed by the first fermentation after 2 h, and the second fermentation induced curd formation in milk. However, after 4 h, the first fermentation resulted in higher whey separation and 80 mg% tyrosine content. Gamma-aminobutyric acid (GABA) production was dependent upon the degree of protein hydrolysis by first fermentation. Second fermentation resulted in 0.14% GABA. The milk fermented by B. subtilis -indicated the rough surface of yogurt depended upon the degree of protein hydrolysis. In conclusion, set-type yogurt was efficiently produced by co-culturing of milk, and fortifying with peptides, GABA, and probiotics.
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