Almeida M J, Pais C
Departamento de Biologia, Universidade do Minho, Braga, Portugal.
Appl Environ Microbiol. 1996 Dec;62(12):4401-4. doi: 10.1128/aem.62.12.4401-4404.1996.
Strains of Saccharomyces cerevisiae and Torulaspora delbrueckii isolated from traditional bread doughs displayed dough-raising capacities similar to the ones found in baker's yeasts. During storage of frozen doughs, strains of T. delbrueckii (IGC 5321, IGC 5323, and IGC 4478) presented approximately the same leavening ability for 30 days. Cell viability was not significantly affected by freezing, but when the dough was submitted to a bulk fermentation before being stored at -20 degrees C, there was a decrease in the survival ratio which depended on the yeast strain. Furthermore, the leavening ability after 4 days of storage decreased as the prefermentation period of the dough before freezing increased, except for strains IGC 5321 and IGC 5323. These two strains retained their fermentative activity after 15 days of storage and 2.5 h of prefermentation, despite showing a reduction of viable cells under the same conditions. The intracellular trehalose content was higher than 20% (wt/wt) in four of the yeasts tested: the two commercial strains of baker's yeast (S. cerevisiae IGC 5325 and IGC 5326) and the two mentioned strains of T. delbrueckii (IGC 5321 and IGC 5323). However, the strains of S. cerevisiae were clearly more susceptible to freezing damages, indicating that other factors may contribute to the freeze tolerance of these yeasts.
从传统面包面团中分离出的酿酒酵母和戴尔布有孢圆酵母菌株表现出与面包酵母相似的面团发酵能力。在冷冻面团储存期间，戴尔布有孢圆酵母菌株（IGC 5321、IGC 5323和IGC 4478）在30天内表现出大致相同的发酵能力。细胞活力并未受到冷冻的显著影响，但当面团在-20℃储存前进行一次批量发酵时，存活率会下降，这取决于酵母菌株。此外，除了IGC 5321和IGC 5323菌株外，随着冷冻前面团预发酵时间的增加，储存4天后的发酵能力会下降。尽管在相同条件下活细胞数量有所减少，但这两个菌株在储存15天和预发酵2.5小时后仍保留其发酵活性。在所测试的四种酵母中，细胞内海藻糖含量高于20%（重量/重量）：两种商业面包酵母菌株（酿酒酵母IGC 5325和IGC 5326）以及上述两种戴尔布有孢圆酵母菌株（IGC 5321和IGC 5323）。然而，酿酒酵母菌株显然更容易受到冷冻损伤，这表明其他因素可能有助于这些酵母的耐冻性。
