Yeast cell mortality related to a high-pressure shift: occurrence of cell membrane permeabilization |
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Authors: | J. -M. Perrier-Cornet M. Hayert P. Gervais |
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Affiliation: | Laboratoire de Génie des Procédés Alimentaires et Biotechnologiques, E.N.S.B.A.N.A., Dijon, France. |
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Abstract: | The shrinkage of yeast cells caused by high-pressure treatment (250 MPa, 15 min) was investigated using direct microscopic observation. A viable staining method after treatment allowed the volume variation of two populations to be distinguished: an irreversible volume decrease (about 35% of the initial volume) of pressure-inactivated cells during pressure holding time, and viable cells, which were less affected. A mass transfer was then induced during high-pressure treatment. Causes of this transfer seem to be related to a pressure-induced membrane permeabilization, allowing a subsequent leakage of internal solutes, where three ions (Na+, K+ and Ca2+), plus endogenous glycerol, were verified. This glycerol leakage was found to occur after yeast pressurization in a medium having low water activity, although the yeast was not inactivated. All these observations lead to the hypothesis that pressure-induced cell permeabilization could be the cause of yeast inactivation under pressure. |
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