Microbiological quality of fermented milk produced by repeated-batch culture.
Using a starter culture containing Lactococcus lactis subsp. cremoris and Acetobacter orientalis, repeated-batch culture for fermented-milk production was carried out for 14 d. The pH decreased to approximately 4.3 and the milk solidified stably when the mixing ratio of fermented-milk to fresh milk was set at a level as high as 10%. The microbial population gradually changed as the culture progressed, and the cell densities of lactic and acetic acid bacteria finally leveled off to constant values. The quality of the fermented-milk became almost constant with respect to the changes in the cell densities of the lactic and acetic acid bacteria. Escherichia coli was then inoculated into the fermented-milk to simulate household contamination. E. coli was washed out with the progress of the repeated-batch culture, and thus showed no adverse effects on the fermented-milk production.
Nakasaki
Kiyohiko
K
Department of Material Sciences and Chemical Engineering, Shizuoka University, Hamamatsu, Japan. tcknaka@ipc.shizuoka.ac.jp
Yanagisawa
Mitsunori
M
Kobayashi
Koji
K
D019342:Acetic Acid / Q000032:analysis; D000091:Acetobacter / Q000302:isolation & purification*; D018929:Cell Culture Techniques / Q000379:methods*; D015169:Colony Count, Microbial; D043302:Cultured Milk Products / Q000382:microbiology*; D004926:Escherichia coli / Q000302:isolation & purification; D005285:Fermentation; D005506:Food Contamination; D005516:Food Microbiology; D019344:Lactic Acid / Q000032:analysis; D013294:Lactococcus lactis / Q000302:isolation & purification*
D019344:Lactic Acid; D019342:Acetic Acid