Nutritional value of yogurt.

Yogurt, made from fortified skim milk by conventional methods using Streptococcus thermophilus and Lactobacillus bulgaricus, was used in studies of the effect of fermentation on nutritional value of milk. In all experiments, the product was compared with the uninoculated base milk. The concentration of most vitamins was less in yogurt than in milk and was most noticeably so for biotin which was 60% less. The effect on folic acid content was inconsistent. In nutritional experiments with rats, high values for true digestibility, biological value and net protein utilization were obtained for both yogurt and its base milk, only minor differences being apparent between the two materials. In growth tests with rats, yogurt was not found to be consistently superior to the base milk when the milk was subjected to a double heat treatment to reduce bacterial contamination. Yogurt did not confer a nutritional advantage on fresh milk in this respect.