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Appl. Environ. Microbiol., 12 1996, 4401-4404, Vol 62, No. 12
MJ Almeida and C Pais
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.
Copyright © 1996, American Society for Microbiology
Leavening ability and freeze tolerance of yeasts isolated from traditional corn and rye bread doughs
Departamento de Biologia, Universidade do Minho, Braga, Portugal.
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