The influence of temperature on glucose metabolism of a psychrotrophic strain of Bacillus cereus was investigated. The pH of the growth medium and sporeforming frequencies of B. cereus varied when grown at 32, 20, or 7 C. Radiorespirometric analyses revealed that vegetative cells of B. cereus metabolized glucose by simultaneous operation of the Embden-Meyerhof-Parnas pathway and the pentose phosphate pathway. As the growth temperature decreased, glucose was metabolized with increased participation of the pentose phosphate pathway. The shift of cells grown at a higher temperature to a lower temperature increased the relative participation of the pentose phosphate pathway, whereas the shift of cells grown at low temperatures to a higher temperature had the opposite effect. Cells of late logarithmic phase grown at 20 and 7 C oxidized acetate by the tricarboxylic acid cycle reaction. However, cells grown at 32 C failed to oxidize acetate to CO2 to any appreciable extent. The extracellular products resulting from the metabolism of glucose decreased as the growth temperature was lowered. Organic acids were the major extracellular products of cultures grown at 32 and 20 C. Acetic acid, lactic acid, and pyruvic acid together accounted for 86.1 and 78.9%o of extracellular radioactivity, respectively, at the two temperatures. The relative ratio of these three acids varied between the temperatures. Little or no acid accumulated at 7 C.
Airborne viable particle counts in the milk processing areas of 10 dairy plants averaged 14 molds and 32 non-molds/10 liters. The bacteria isolated were primarily micrococci, Gram-negative rods (excluding coliform), bacilli, and coryne-bacteria. Twenty-five per cent of the isolates grew at 10 C in 5 days. These were principally bacilli and Gram-negative rods (excluding coliform). There was no apparent relationship between airborne microbial populations and keeping quality of the packaged milk.
Processed meat loaves were prepared with dry whey, and ultrafiltrated whey protein concentrates containing 18.7% (WPC-1520) and 32.5% (WPC-3035) protein ,along with a control containing nonfat dry milk (NDM). Binding .strength; as measured by Instron shear, and tenderness, as evaluated by a taste panel, of the'NDM and three whey treatments were not different. A taste panel, using the triangle test, could not differentiate the NDM and WPC-1520 (P > 0.05), but did differentiate all other comparisons (P < 0.05). Higher sensory panel ratings for flavor were .given to samples containing dry whey (P'< 0.05), possibly because of flavor enhancement resulting from the high level of 'lactose contributed by dry whey. Similarly more desirable juiciness ratings by the panel given to samples containing WPC-3035 (P < 0.05) may possibly be attributed to the water-binding characteristics of the high levels of whey protein.
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