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Effects of Yeast Freezing in Frozen Dough

¹Facultad de Ciencias Agropecuarias, Universidad Nacional de Córdoba, Av. Valparaíso s/n, C.C. 509, Córdoba (5000), Argentina. ²Centro de Investigación y Desarrollo en Criotecnología de Alimentos (CONICET, UNLP), calle 47 y 116, C.C. 553, La Plata (1900), Argentina. ³Corresponding author. E-mail: pribotta@agro.uncor.edu. Phone: 54-351-4334116/17. Fax: 54-351-4334118.

The effects of freezing and frozen storage of bread dough and compressed yeast on bread quality were studied. Besides, the effects of compressed yeast freezing on cell viability, gas production and release of substances by the yeast cells were examined. Freezing and frozen storage of dough made with fresh yeast had more negative effects on baking quality than the addition of frozen yeast to dough. When the compressed yeast is frozen and stored at -18°C, the CO₂ production decreased, while the amount of dead cells, the total protein, and the total reducing substances leached from the yeast increased as the length of yeast frozen storage increased. SDS-PAGE showed that the substances leached from frozen yeast caused an increase in the solubility of some gluten proteins. On the other hand, size-exclusion chromatography (SEC) pointed out that the relative amount of two protein fractions of low molecular weight leached from frozen yeast increased for longer yeast frozen storage periods. The yeast leachates had an adverse effect on loaf volume.