Survival of Lactobacillus acidophilus in “Sweet Acidophilus Milk” during Refrigerated Storage

Abstract

Samples of three brands of commercial “Sweet Acidophilus Milk” were obtained directly from the processors and evaluated periodically for microbial, chemical, and flavor changes during 23–24 days of storage at 4 ± 2 C. Counts of Lactobacillus acidophilus decreased from 2.6 × 106–6.4 × 106/ml initially to 5.1 × 104–3.1 × 106/ml at the end of the study. Several samples dropped below 2 × 106 viable L. acidophilus before the pull date was reached. Final contaminant counts were 106 – 106/ml in all samples, but rate of decline of L. acidophilus was not directly related to growth of contaminants. Titratable acidity and pH changed very little, and yeast and mold growth was minor. Notable off-flavors developed in 14–21 days.