Beuchat Larry R
Department of Food Science, University of Georgia Agricultural Experiment Station, Experiment, Georgia 30212.
J Food Prot. 1983 Feb;46(2):135-141. doi: 10.4315/0362-028X-46.2.135.
The behavior of yeasts and molds as influenced by water activity (a) is reviewed. Fungal spoilage of foods occurs more often than bacterial spoilage at a 0.61-0.85 not because fungi grow faster at reduced a but rather because the competitive effects of the vast majority of bacteria are absent. Higher a is generally required for spore formation than for spore germination. The range of a permitting germination of spores is greatest at an optimum temperature, but optimum availability of nutrients tends to broaden the range of a and temperature at which germination and growth will occur. The minimum a levels for growth of fungi are lower than those required for mycotoxin production. It is imperative that diluents and enumeration media with reduced a 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 a associated with diluents and media routinely used for mycological analyses.
综述了水分活度（a）对酵母和霉菌行为的影响。在水分活度为0.61 - 0.85时，食品的真菌腐败比细菌腐败更常见，这并非因为真菌在较低水分活度下生长更快，而是因为绝大多数细菌的竞争作用不存在。孢子形成通常比孢子萌发需要更高的水分活度。孢子萌发允许的水分活度范围在最适温度下最大，但营养物质的最佳可利用性往往会拓宽孢子萌发和生长所发生的水分活度和温度范围。真菌生长的最低水分活度水平低于产生霉菌毒素所需的水平。必须使用水分活度降低的稀释剂和计数培养基来检测食品中的耐干性真菌。否则，营养细胞和孢子可能会因渗透冲击而死亡，或者在暴露于与常规用于真菌学分析的稀释剂和培养基相关的高水分活度时保持休眠状态。
