Revista de microbiología industrial y alimentaria

When a food is spoiled, its characteristics are changed so that it is no longer acceptable. Such changes might not generally be microbiological in origin; a product can also become unacceptable due to insect damage, drying out, discolouration, staling or rancidity for instance, however most food spoilage is an end result of microbial activity. Microbiological food spoilage can happen in numerous exclusive ways, a number of which frequently arise in combination. Visible microbial growth can be obvious in the form of surface slime or colonies, degradation of structural components of the food can cause a loss of texture; anyway the most widely recognized sign can be chemical products of microbial metabolism, gas, pigments, polysaccharides, offodours and flavours. A general feature of microbial spoilage is its rather unexpected onset; it does not seem to grow progressively, day by day a little worse, yet more regularly as an unexpected and unpleasant revelation. This is an impression of the exponential nature of microbial multiplication and its result that microbial metabolism can also proceed at an exponentially increasing rate.

Tea, brewed from leaves and twig of Camellia sinensis, is considered as most widely consumed beverage after water. Tea can be classified as raw or unfermented green tea; partially fermented Oolong (red and yellow) tea; totally fermented black tea. Tea possesses significant antioxidative, antiinflammatory, antimicrobial, anticarcinogenic, antihypertensive, neuroprotective, cholesterollowering, and thermogenic properties. Green tea comprises of certain active components such as polyphenols, caffeine amino acids, flavonoids. Herbal tea or ‘tisanes’ is essentially an herbal mixture made from leaves, seeds and/ or roots of various plants. Herbal tea possesses certain medicinal properties such as anti-bacterial, anti- inflammatory properties. The objective of this review is to discuss various types of tea including herbal tea, summarizing their health benefits, preparations.

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.