Quality audit data collected as part of a mass feeding quality assurance program were analyzed to determine the relationships between the indicator tests (total aerobic plate count, coliform count and Escherichiu colz) and the common food-borne pathogens (Staphylococcus aureus, Clostridium perfringens and Salmonella). 132 raw foods and 593 readyto-eat foods were evaluated. The indicators were grouped into ranges and compared to the pathogens and to each other in terms of detectability. There were correlations between the pathogens and the indicator ranges and between the indicators and the indicator ranges. The value of the indicators in the e'valuation of food safety was tested by setting standards and determining the numbers of correct and incorrect decisions which would be made relative to the pathogens detected in the foods. None of the indicators was suitable as a screening agent for food safety.

The mechanism responsible for an increased rate of acid production when yogurt starter cultures are grown in milk treated with lactase enzyme was investigated by studying carbohydrate utilization and acid development by a pure culture of Streptococcus thermophilus and a mixed yogurt starter culture consisting of S. thermophilus and Lactobacillus bulgaricus . In milk containing glucose, galactose, and lactose, glucose and lactose (but not free galactose) were fermented. Fermentation of lactose in control milk was accompanied by the release of free galactose, with the result that carbohydrate utilization was less efficient than in treated milk. This phenomenon also occurred when lactose was fermented by S. thermophilus in broth culture. Carbohydrate utilization by the mixed yogurt culture was more rapid when the lactose in milk was partially prehydrolyzed. Our results suggest that the more rapid acid development that took place when a mixed yogurt starter culture was grown in milk containing prehydrolyzed lactose was the result of a more rapid and efficient utilization of carbohydrate by S. thermophilus when free glucose in addition to lactose was available for fermentation. The evidence presented also suggests that uptake and utilization of glucose and lactose by S. thermophilus are different in broth and milk cultures.

SummaryAlcohol yields of 6.5% were obtained with Saccharomyces cerevisiae in lactasehydrolyzed acid whey permeate containing 30-35% total solids. Maximum alcohol yields obtained with Kluyveromyces fragilis were 4.5% in lactase-hydrolyzed acid whey permeate at a solids concentration of 20% and 3.7% in normal permeate at a solids concentration of 10%. Saccharomyces cerevisiae efficiently converted the glucose present in lactase-hydrolyzed whey permeates containing 5-30% total solids (2-13% glucose) to alcohol. However, the galactose, which comprised about half the available carbohydrate in lactase-hydrolyzed whey, was not utilized by S . cerevisiae, so that even though alcohol yields were higher when this organism was used, the process was wasteful in that a substantial proportion of the substrate was not fermented. For the process to become commercially feasible, an efficient means of rapidly converting both the galactose and glucose to alcohol must be found.

SummaryEthanol production by Kluyveromyces fragilis and Saccharomyces cerevisiae was studied using cottage cheese whey in which 80 to 90% of the lactose present had been prehydrolyzed to glucose and galactose. Complete fermentation of the sugar by K . fragilis required 120 hr at 30°C in lactase-hydrolyzed whey compared to 72 hr in nonhydrolyzed whey. This effect was due to a diauxic fermentation pattern in lactase-hydrolyzed whey with glucose being fermented before galactose. Ethanol yields of about 2% were obtained in both types of whey when K . fragilis was the organism used for fermentation. Saccharomyces cerevisiae produced alcohol from glucose more rapidly than K . jragilis, but galactose was fermented only when S. cerevisiae was pregrown on galactose. Slightly lower alcohol yields were obtained with S. cerevisiae, owing to the presence of some lactose in the whey which was not fermented by this organism. Although prehydrolysis of lactose in whey and whey fractions is advantageous in that microbial species unable to ferment lactose may be utilized, diauxie and galactose utilization problems must be considered.