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.

Influence of Freeze-Dried Yeast Starter Cultures on Volatile Compounds of Tchapalo, a Traditional Sorghum Beer from Côte d’Ivoire

“…Recently, we showed the possibility of producing freeze-dried starter culture for the brewing purpose of tchapalo with sucrose and cassava flour as the best protective agent and support material, respectively [20]. In this study, we aimed to evaluate the capacity of S. cerevisiae and C. tropicalis to produce sorghum beer as freeze-dried starter culture.…”

“…After homogenization, samples were transferred into sterilized flasks, frozen in a freezer (SANYO, Medical freezer, MDF 235) for 24 h at −80 • C and subsequently freeze-dried with a freeze drier (Alpha 1-4 Christ, Fischer Scientific, Bioblock, France) at −60 • C for 32 h under vacuum degree of 6.7-13.3 Pa (50-100 mTorr). Immediately after drying, water content and viability of the freeze-dried biomass were evaluated as previously described by several authors [20].…”

Non-Saccharomyces yeasts and their importance in the brewing industry. Part II

“…Smíše-ná kultura podporuje produkci ethanolu (N'Guessan et al, 2010). Tato směs může být lyofi lizována a uchovávána po delší dobu, což zajišťuje lepší kvalitu výroby tradičních afrických piv (N'Guessan et al, 2016).…”

“…The mixed culture supports ethanol production (N'Guessan et al, 2010). The mixture can also be lyophilized and stored for a longer period, thus ensuring better quality of traditional African beers (N'Guessan et al, 2016).…”

Isolation and molecular identification of yeast strains from Rabil a starter of local fermented drink

“…Sorghum beer is a popular alcoholic beverage from African countries where sorghum is produced (Maoura et al, 2005;N'Guessan et al, 2016). The beers are consumed at various festivals and African ceremonies and constitute a source of incomes for beer women producers (Lyumugabe et al, 2012;Djêgui et al, 2015).…”