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Ultrahigh temperature sterilized canned puddings occasionally exhibit spoilage in the form of a dramatic loss of viscosity or thinning. Studies on a concentrated fraction of spoiled pudding indicate that thinning was due to a heat-resistant amylase. The concentrate was obtained by centrifugation and ultrafiltration of the thinned pudding. Ultrafiltration characteristics of the active agent indicate a molecular weight of 1–30 × 104 daltons. The agent attacked starch with a decrease in iodine-binding capability and an increase in reducing units. Treatment of the concentrate with proteolytic enzymes decreased enzymatic activity by 50%; treatment with sodium ethylene diaminetetraacetate decreased activity by 80%. The levels of starch and pH of the spoiled puddings were suitable for action of the amylase, and the enzyme was quite active at normal and elevated room temperatures.

The α-amylase of the thermophile Bacillus stearothermophilus 1518 was used as a model enzyme to examine the heat resistance of a bacterial amylase at ultrahigh temperature in a starch-based pudding. When heated in the laboratory pudding at 143°C for the equivalent of 22.2 set, approximately 26% of the initial amylolytic activity was retained. The presence or absence of individual ingredient groups (starch, caseinate-nonfat dry milk, oilemulsifiers, salts, or sucrose) of the pudding had no significant effect on amylase heat resistance. A combination of any two of the starch, caseinate-nonfat dry milk, or oil-emulsifier ingredients were found to be important for thermostability. The amylase of the mesophile Xanthomonas campestris 13957–2 exhibited similar thermal inactivation characteristics.

Modified PA3679 agar (MPA3679A) was formulated as a plating medium to provide improved recovery of Clostridium sporogenes Putrefactive Anaerobe (PA) 3679 spores. A comparative study of MPA3679A and two currently used plating media, Yeast extract agar (YEA), and Peptone trypticase agar (PTA), showed that MPA3679A was superior for the recovery of heat activated and heat stressed spores. Further, when this medium was altered for use as an inoculated pack subculture medium, recovery of severely heat stressed spores was superior to that in the previously recommended PA3679 agar, also known as T-Best.

The heat resistant lipase of Pseudomonas spp. MC50 hydrolyzed coconut oil, corn oil, butter oil and olive oil. Lipase activity was maximum at 1% corn oil. The effects of pH and temperature on lipase activity varied with the substrate. The pH optima were in the range pH 8–9; the temperature optima were in the range 35–40°C. Of several emulsifiers tested, four supported significant lipase actiivity, and three supported no lipase activity and may have inhibited the lipase. Emulsifier concentration influenced lipase activity. All stabilizers tested supported lipase activity; above 0.36% stabilizer concentration had no effect.

Pseudomonas spp. MC50 produced an extra-cellular lipase that was extremely heat resistant at 100–150°C when heated in water or emulsions. The D-values ranged from 40 min at 100°C to 84 sec at 150°C. The zD-vallue was 36°C. When heated in water, the lipase exhibited greatest survival at pH 8.5. Below pH 6.5, survival was less than 10% of that at pH 8.5. Survival of lipase heated in emulsions was affected somewhat by the type of oil, corn oil concentration, and type of emulsifier. Type of stabilizer or stabilizer concentration had little effect on lipase survival. Lipase treated with ethylenediaminetetraacetate (EDTA) was fully heat resistant in water; survival declined when lipase was heated in CaCl2 solutions of 3–120 mM.