title: Production of freeze-dried yeast culture for the brewing of traditional sorghum beer, tchapalo.
abstract: Freeze-drying is a well-known dehydration method widely used to preserve microorganisms. In order to produce freeze-dried yeast starter culture for the brewing purpose of African sorghum beer, we tested protective agents (sucrose, glucose, glycerol) in combination with support materials (millet, maize, sorghum, and cassava flours) at 1:1 ratio (v/v). The yeast strains Saccharomyces cerevisiae F 12-7 and Candida tropicalis C 0-7 previously isolated from sorghum beer were used in a mixed culture at a ratio of 2:1 (C. tropicalis/S. cerevisiae). After the freeze-drying, the residual water contents were between 0.78 -2.27%, 0.55 -4.09%, and 0.40-2.61%, respectively, with sucrose, glucose and glycerol. The dried yeasts viabilities were between 4.0% and 10.6%. Among the protective agents used, sucrose was found to be the best protectant giving cell viabilities of 8.4-10.6%. Considering the support materials, millet flour was the best support after drying. When the freeze-dried yeast powders were stored at 4°C and room temperature (25-28°C) for up to 3 months, the survival rates were the highest with cassava flour as the support material.
authors.affiliation: Laboratoire de Biotechnologie et Microbiologie des Aliments Unité de Formation et de Recherche en Sciences et Technologie des Aliments (UFR-STA) Université Nangui-Abrogoua 02 BP 801 Abidjan 02 Côte d'Ivoire.
authors.forename: Florent K
authors.initials: FK
authors.lastname: N'Guessan
authors.affiliation: Laboratoire de Biotechnologie et Microbiologie des Aliments Unité de Formation et de Recherche en Sciences et Technologie des Aliments (UFR-STA) Université Nangui-Abrogoua 02 BP 801 Abidjan 02 Côte d'Ivoire; Laboratoire d'Ingénierie des Systèmes Biologiques et Procédés Institut National des Sciences Appliquées (INSA-Toulouse) 135 Avenue de Rangueil 31077 Toulouse Cedex 4 France.
authors.forename: Hermann W
authors.initials: HW
authors.lastname: Coulibaly
authors.affiliation: Laboratoire de Biotechnologie et Microbiologie des Aliments Unité de Formation et de Recherche en Sciences et Technologie des Aliments (UFR-STA) Université Nangui-Abrogoua 02 BP 801 Abidjan 02 Côte d'Ivoire; Centre Wallon de Biologie Industrielle (CWBI) Unité de Bio-industries, Université de Liège Gembloux Agrobio-Tech Passage des Déportés 25030 Gembloux Belgium.
authors.forename: Mireille W A
authors.initials: MW
authors.lastname: Alloue-Boraud
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Biologiques et Procédés Institut National des Sciences Appliquées (INSA-Toulouse) 135 Avenue de Rangueil 31077 Toulouse Cedex 4 France.
authors.forename: Marlène
authors.initials: M
authors.lastname: Cot
authors.affiliation: Laboratoire de Biotechnologie et Microbiologie des Aliments Unité de Formation et de Recherche en Sciences et Technologie des Aliments (UFR-STA) Université Nangui-Abrogoua 02 BP 801 Abidjan 02 Côte d'Ivoire.
authors.forename: Koffi Marcellin
authors.initials: KM
authors.lastname: Djè
keywords: Freeze‐drying; protective agent; sorghum beer; storage; support material; survival; yeast