CRYORESISTANCE OF BAKERS-YEAST SACCHAROMYCES-CEREVISIAE IN FROZEN DOUGH - CONTRIBUTION OF CELLULAR TREHALOSE

The effects of freezing on gas production of two baker's yeast strains (A and B) were studied in dough. A specific parameter, the mean volum e (vol(m)), obtained from the area under the gassing curve was shown t o be the best expression of overall yeast dynamics during fermentation . Assessing the specific freeze-thaw and frozen storage resistances of yeasts showed that strain B was particularly cryoresistant. Immediate freeze-thaw resistance of both yeasts was unaffected by 1 or 2 hr of prefermentation before freezing, which is not the case for frozen stor age resistance. The possible cryoprotective role of cellular trehalose was then examined by following the changes in yeast trehalose content in dough. Cryoresistance was not directly correlated with the initial amount of trehalose in the yeast nor with the level still present in the dough at the time of freezing. However, when the trehalose level d ropped below 5%, the delayed frozen storage resistance was clearly low ered. A 4-5% trehalose content at freezing appeared to be sufficient t o prevent yeast from indirect chilling injury during frozen storage. A higher quantity of cellular trehalose does not contribute to further cryoresistance.