Maize flour is a promising and low-cost carrier material for producing freeze-dried starter cultures adapted to cereal fermentation in West Africa

Abstract

Food fermentations in West Africa are still conducted spontaneously because of the lack of knowledge, unavailability of adequate technologies and the lack of production facilities. This study aimed at using maize flour as carrier material to develop a multifunctional freeze-dried starter culture with a mixture of lactic acid bacteria (LAB) and yeast strains. The maize flour carrier was tested for microorganisms’ freeze-drying, water activity (aw) as well as microbial viability. Two commercial carrier materials, i.e. soluble starch and skimmed milk, were used for comparison. After microbial freeze-drying, similar aw values (aw = 0.05–0.06) were obtained with the maize flour and the commercial carriers, i.e. skimmed milk and soluble starch. A slight increase of aw (0.07–0.08) was observed with the maize flour after 15 and 45 days storage at 4°C. For the three carrier materials, similar microbial log reduction (1.78–1.35 units with Lactobacillus fermentum Lf and 0.73–0.67 units with Saccharomyces cerevisiae Sc) was recorded just after freeze-drying and remained constant after 15 and 45 days storage at 4°C. Further, a defined freeze-dried starter culture was developed using the maize flour carrier as for a mixed culture of LAB and yeast strains. The defined freeze-dried culture showed stable fermentation activity during storage. The results indicated that the maize flour-based carrier could be suitable for microbial freeze-drying. Therefore, installing starter culture production facilities in West Africa to control cereal fermentation is possible. It will contribute to upgrading the sector of cereal food in this part of the world.

Keywords

• multifunctional starter culture
• cereal fermentation
• freeze-drying
• lactic acid bacteria
• yeasts