title: Effect of growth conditions and trehalose content on cryotolerance of bakers' yeast in frozen doughs.
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 degrees C min. 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 (mu = 0.088 h compared with 0.117 h) also showed greater trehalose synthesis and improved frozen-dough stability. Insufficient aeration (dissolved-oxygen deficit) and lower growth temperature (20 degrees C instead of 30 degrees 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.
authors.affiliation: Lallemand Inc., Montreal, Quebec H1W 2N8, Canada, and Département de Sciences et Technologie des Aliments and Département de Génie Chimique, Université Laval, Sainte-Foy, Quebec G1K 7P4, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Gélinas
authors.forename: G
authors.initials: G
authors.lastname: Fiset
authors.forename: A
authors.initials: A
authors.lastname: Leduy
authors.forename: J
authors.initials: J
authors.lastname: Goulet