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Appl Environ Microbiol. Oct 1989; 55(10): 2453–2459.
PMCID: PMC203104
Effect of Growth Conditions and Trehalose Content on Cryotolerance of Bakers' Yeast in Frozen Doughs
Pierre Gélinas,1,2* Gisèle Fiset,2 Anh LeDuy,3 and Jacques Goulet2
1Lallemand Inc., Montreal, Quebec H1W 2N8, Canada, and Département de Sciences et Technologie des Aliments2 and Département de Génie Chimique, 3 Université Laval, Sainte-Foy, Quebec G1K 7P4, Canada
* Corresponding author.
Present address: Agriculture Canada, Food Research and Development Centre, 3600 Casavant Boulevard West, Saint-Hyacinthe, Quebec J2S 8E3, Canada.
Abstract
The cryotolerance in frozen doughs and in water suspensions of bakers' yeast (Saccharomyces cerevisiae) previously grown under various industrial conditions was evaluated on a laboratory scale. Fed-batch cultures were very superior to batch cultures, and strong aeration enhanced cryoresistance in both cases for freezing rates of 1 to 56°C min−1. Loss of cell viability in frozen dough or water was related to the duration of the dissolved-oxygen deficit during fed-batch growth. Strongly aerobic fed-batch cultures grown at a reduced average specific rate (μ = 0.088 h−1 compared with 0.117 h−1) also showed greater trehalose synthesis and improved frozen-dough stability. Insufficient aeration (dissolved-oxygen deficit) and lower growth temperature (20°C instead of 30°C) decreased both fed-batch-grown yeast cryoresistance and trehalose content. Although trehalose had a cryoprotective effect in S. cerevisiae, its effect was neutralized by even a momentary lack of excess dissolved oxygen in the fed-batch growth medium.
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