Date of Award:
Master of Science (MS)
Nutrition, Dietetics, and Food Sciences
Department name when degree awarded
Nutrition and Food Sciences
Five strains of Lactococcus lactis were inoculated individually into six commercial bulk set growth media, 11% non-fat dry milk (NDM), and Elliker's broth. After growth in each medium the strains were tested for rate of acid production, and activities of proteinase, aminopeptidase, and lipase/esterase. Growth in commercial starter media significantly influenced acid production rate (P = 0.040), aminopeptidase activity (P < 0.0001), and lipase/esterase activity (P < 0.0001) .
For selected strain/media combinations, the duration of induced aminopeptidase and lipase/esterase activity was followed. The chosen strains were grown in selected commercial bulk set media, reinoculated into 11% NDM, and enzyme activity was examined for five successive generations. During growth in 11% NDM, aminopeptidase and lipase/esterase activity began high and appeared to decrease after approximately two generations, as compared to the control.
This study demonstrated that it is possible to select specific starter and media combinations to produce a bacterial phenotype that might not change before the cheese is pressed, thereby trapping bacteria with an altered phenotype within the cheese matrix.
DeVries, Norman Bart, "Influence of Commercial Starter Media on Biochemical Characteristics of Lactococcus lactus" (1999). All Graduate Theses and Dissertations. 5462.
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