Zeitschrift für Lebensmittel- und Industriemikrobiologie

Microbiology of Food preservation

Abstract

Surya Kumar

Psychrotrophs are less heat resistant than mesophiles, which are in turn less heat resistant than thermophiles; and Gram- positives are more heat resistant than Gram-negatives. Most vegetative cells are killed instantaneously at 100°C. Bacterial spores are undeniably more heat resistant than vegetative cells; thermophiles produce the most heat resistant spores while those of psychrotrophs and psychrophiles are most heat sensitive. Since spore inactivation is the chief concern in producing appertized foods, much higher temperatures are utilized in appertization processes. Yeast ascospores and the asexual spores of moulds are just somewhat more heat resistant than the vegetative cells and will regularly be killed by temperatures at or below 100°C, for example in the baking of bread. Ascospores of the mould Byssochlamys fulva, and a few other ascomycetes do show a more marked heat resistance and can be an incidental reason for issues in canned fruits which get a relatively mild heat process.