Microbiological and chemical parameters during cassava based-substrate fermentation using potential starter cultures of lactic acid bacteria and yeast

Abstract

Traditional Brazilian indigenous fermented foods and beverages are potential sources of new food products that promote health, but they are still produced by natural fermentation. In the present work, Lactobacillus fermentum CCMA 0215 isolated from the indigenous fermented cassava beverage yakupa was used as single or mixed starter culture with five different yeast strains (Torulaspora delbrueckii CCMA 0234 and CCMA 0235, Pichia caribbica CCMA 0198, and Saccharomyces cerevisiae CCMA 0232 and CCMA 0233) to ferment cassava. Fermentations using each yeast as single starter culture were also performed. The microbial population and metabolites produced during cassava fermentation were investigated. In all assays, the inoculated microorganisms fermented cassava, judged by lowering the pH from 6.0 to 4.0–5.0 within 24h. Lactic acid bacteria (LAB) and yeast population increased during fermentation. Lactic acid was the main organic acid produced, reaching a maximum value of 4.5g/L at 24h in the co-culture with L. fermentum CCMA 0215 and T. delbrueckii CCMA 0234. Other organic acids, such as malic, tartaric, and succinic acids, were detected in low concentrations (less than 0.5g/L). Ethanol and glycerol were produced in all assays inoculated with yeasts (single and co-cultured with LAB), reaching the maximum concentration of approximately 2.3g/L and 0.6g/L, respectively. Twenty-two volatile compounds were detected after 48h of fermentation, varying widely between single and co-cultures. The compounds 2-phenylethyl alcohol, 1-butanol, 3-methyl (isoamyl alcohol), and acetoin were detected in single and co-cultures. This study demonstrated co-cultures of yeasts and LAB had the ability to improve the aroma profile of the final product and the safety of the product by lowering the pH.