Influence of water activity on growth, metabolic activities and survival of yeasts and molds
1983
Beuchat, Larry R.
Extract: The behavior of yeasts and molds as influenced by water activity (WA) is reviewed. Fungal spoilage of foods occurs more often than bacterial spoilage at WA 0.61-0.85, not because fungi grow faster at reduced WA, but rather because the competitive effects of the vast majority of bacteria are absent. Higher WA is generally required for spore formation than for spore germination. The range of WA permitting germination of spores is greatest at an optimum temperature, but optimum availability of nutrients tends to broaden the range of WA and the temperature at which germination and growth will occur. The minimum WA levels for growth of fungi are lower than those required for mycotoxin production. It is imperative that diluents and enumeration media with reduced WA be used to detect xerotolerant fungi in foods. Otherwise, vegetative cells and spores may be killed by osmotic shock or remain dormant when exposed to high WA associated with diluents and media routinely used for mycological analyses. (author)
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