Effect of protective agents on the viability of geotrichum candidum during freeze-drying and storage |
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Authors: | Hamoudi Latifa Goulet Jacques Ratti Cristina |
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Affiliation: | Authors Hamoudi and Ratti are with Dépt. des sols et de génie agroalimentaire, Univ. Laval, Pavillon Comtois, FSAA, Ste-Foy, QC G1K 7P4, Canada. Author Goulet is with Dépt. des sciences des aliments et nutrition, Univ. Laval, Pavillon Comtois, FSAA, Ste-Foy, QC G1K 7P4, Canada. Direct inquiries to author Ratti (E-mail: ). |
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Abstract: | ABSTRACT: The effect of 3 cryoprotective agents (trehalose, sucrose, and maltose) on the survival of concentrated cultures of Geotrichum candidum was studied. Initially, the effect of the carbohydrates at 9% and 23% concentrations or combined with skim milk (16%) was compared to the control (skim milk alone) immediately after freeze-drying. Two freeze-drying shelf temperatures, 25 °C and 35 °C, were investigated. Afterwards, the survival of G. candidum freeze-dried with carbohydrates at 23% concentration (alone or combined with skim milk 16%) was studied during 12 wk of storage at 4 °C, in the darkness, under vacuum, and at 0% relative humidity. The glass transition temperature ( Tg ) of the dehydrated protective agents was measured by differential scanning calorimetry. The results showed that the survival after freeze-drying was proportional to the concentration of the protective agents, with skim milk alone giving poor survival of G. candidum . However, when skim milk was combined with disaccharides, a clear improvement was noted. No general tendency of shelf temperature on the survival of G. candidum was noted immediately after freeze-drying. However, changes in the viability were observed during storage. Glass transition temperature ( Tg ) of protective agents linked to their moisture may contribute to predict the stability of lyophilized G. candidum during freeze-drying and storage. |
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Keywords: | freeze-drying Geotrichum candidum glass transition temperature protective agents storage |
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