The storage stability of thiamin mononitrate and riboflavin in a low moisture dehydrated model food system was determined as a function of water activity, moisture content and storage temperature. Fortification of the model system was at a level of 25% RDA per 100 g. The model system was equilibrated at water activities below, at and above the calculated water activity corresponding to the monomolecular moisture content for the adsorption isotherms. Thiamin retention was approximately 100% after eight months storage at temperatures from 20–37°C and aw 0.1 to 0.65. Retention of thiamin in the model food system was only 10–20% at 45°C with an aw from 0.40–0.65. Riboflavin retention was approximately 100% after eight months storage at 10 to 20°C with an aw of 0.1 to 0.65 and at 30°C, with an aw of 0.1 to 0.40. At 37°C the loss of riboflavin increased with increasing water activity. The rate of riboflavin destruction dramatically increased in the model system packaged in an oxygen permeable container. A similar effect was not observed in the thiamin study. The stability of thiamin and riboflavin was unaffected by the addition of vitamins A or C.

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A heat-resistant glucose dehydrogenase occurs in cultures of Bacillus cereus which are in the initial stages of sporulation. This enzyme is, kinetically, identical to the glucose dehydrogenase which can be extracted from mature spores, but is considerably more heat resistant than the spore-free enzyme. The two enzymes produce identity lines in two-dimensional immunodiffusion experiments, and their behavior in chromatographic and electrophoretic studies is also identical. A labile glucose dehydrogenase can be extracted from germinated spores of B. cereus. It differs from its stable counterparts in possessing a higher pH optimum for enzymatic activity.

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When polyurethane foam test tube plugs are autoclaved, they release volatile fatty amines that inhibit the growth of some microorganisms. The chemical structures of these amines were determined by the use of a gas chromatographmass spectrometer. They are catalysts used to produce the foam. The problem of contaminating growth media with toxic substances released from polymeric materials is discussed.