Survival of Listeria monocytogenes in yogurt with varying levels of fat and solids
1990
Griffith, M. | Deibel, K.E.
Yogurts with varying levels of fat and solids were fermented with Lactobacillus bulgaricus and Streptococcus thermophilus in the laboratory to a titratable acidity (TA) of .09%. Each yogurt was seeded with one of three strains of Listeria monocytogenes at two levels and survival was monitored at 1-7, 14, 21 and 28 days during storage at 4 degrees C. All strains survived longer in the skim milk/high solids yogurts which had a higher pH than the whole milk/low solids yogurt. To determine the effects of pH, solids and fat, simulated yogurts, prepared by acidifying milk preparations to pH 4.2, 4.1 and 4.0, were inoculated with L. monocytogenes. Survival was affected by differences in pH and solids content and strain L. monocytogenes while fat content had no apparent effect.
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