This study was conducted in an attempt to characterize some of the effects of sublethal microwave radiation on cells of Staphylococcus aureus. Cultures were exposed to microwave radiation for 10, 20, 30, and 40 s. The effects of a conventional heat treatment were also compared by placing flasks containing cultures in a boiling water bath for the amount of time required to reach temperatures equivalent to those found in cultures exposed to microwave radiation. Control, microwave-treated, and conventionally heat-treated cultures were centrifuged, pellets were resuspended in distilled water, and the resulting suspensions were passed through a French pressure cell. Cell lysates and walls were then isolated and assayed for enzymatic activity. Thermonuclease production was also determined at various levels of exposure of cells to microwave radiation. Activities of malate and α-ketoglutarate dehydrogenases, cytochrome oxidase, and cytoplasmic adenosine triphosphatase were higher in microwave-treated cells than in control cells. Membrane adenosine triphosphatase, alkaline phosphatase, and lactate dehydrogenase activities were unaffected when cells were exposed to microwave radiation. The activity of glucose-6-phosphate dehydrogenase was decreased by exposure of cells to microwave radiation. In conventionally heated cells, activities of glucose-6-phosphate and malate dehydrogenases and cytoplasmic adenosine triphosphatase increased activities of α-ketoglutarate and lactate dehydrogenases decreased, and alkaline phosphatase activity remained unaffected. Increased levels of thermonuclease activity were observed when cells were exposed to microwave radiation for 10 or 20 s. Data indicate that microwave radiation affects S. aureus in a manner which cannot be explained solely by thermal effects.

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Use of a precooked frozen entree, hamburger patties, in a satellite foodservice system was assessed as related to time and temperature conditions and microbiological and sensory quality to identify critical phases in utilizing a precooked frozen entree. Time for product storage at the service location was approximately 3 days, and average time at room temperature during assembly was 2 h. Temperature conditions were generally variable with internal temperatures after heating food for service ranging from 152 F (67 C) to 192 F (89 C). Except for some of the low internal temperatures, conditions were acceptable from a food safety standpoint. Mean scores for sensory quality characteristics evaluated ranged from 5.1 to 6.9 (9-point scale) and total plate counts indicated that microbial quality was good. Genera of pathogenic microorganisms were identified, including Clostridium and Staphylococcus; therefore, the potential exists for public health hazards if precooked food is subsequently mishandled in a system of this type. Critical problems may become apparent in the control of variability within the system, particularly, at the point of heating food for service.

A study was conducted to determine the effects of o-nitrobenzoate, p-aminobenzoate, benzocaine (ethyl aminobenzoate), ethyl benzoate, methyl benzoate, salicylic acid (o-hydroxybenzoate), trans-cinnamic acid (,B-phenylacrylic acid), trans-cinnamaldehyde (3-phenylpropenal), ferulic acid (p-hydroxy-3-methoxycinnamic acid), aspirin (o-acetoxy benzoic acid), and anthranilic acid (o-aminobenzoic acid) upon growth and aflatoxin release in Aspergillus flavus NRRL 3145 and A. parasiticus NRRL 3240. A chemically defined medium was supplemented with various concentrations of these compounds and inoculated with spores, and the developing cultures were incubated for 4, 6, and 8 days at 27°C in a mechanical shaker. At the beginning of day 8 of incubation, aflatoxins were extracted from cell-free filtrates, separated by thin-layer chromatography, and quantitated by ultraviolet spectrophotometry. The structure of these aromatic compounds appeared to be critically related to their effects on mycelial growth and aflatoxin release. At concentrations of 2.5 and 5.0 mg per 25 ml of medium, methyl benzoate and ethyl benzoate were the most effective in reducing both mycelial growth and aflatoxin release by A. flavus and A. parasiticus. Inhibition of mycelial growth and aflatoxin release by various concentrations of the above-named aromatic compounds may indicate the possibility of their use as fungicides. Aflatoxins, produced by certain strains of Aspergillus flavus and A. parasiticus, have been well documented as producing significant pathological changes in plants and animals (6, 13). Recent evidence has indicated that aflatoxin may also be involved in the etiology of human liver cancer in certain parts of the world (17).

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