Evolution of yeast population throughout the fermentation of corn flour to produce Chicha

L. MENDOZA; B. PADILLA; F. MOZZI; P.S. COCCONCELLI; G. VIGNOLO; C. BELLOCH

Estambul

Simposio; FoodMicro 2012. 23rd International ICFMH Symposium. Global Issues in Food Microbiology; 2012

Chicha production started with soaking of maize flour with hot water (aprox. 1:1, w/v). After thoroughly mixed and cooled, flat buns were hand shaped and cooked on a tray in a rudimentary clay oven during 1.30 h. After baking was completed, buns were left to cool and grounded by hand, mixed with cane sugar, maize flour and warm water (aprox. 1:1:5:1) and allowed to ferment at ambient temperature (18-20º C) during 7-8 days. The fermented mass was then added to fresh maize flour and warm water (aprox. 1:1:10), mixed thoroughly and allowed to decant and cool for 2-3 h. Three layers, top liquid (supernatant), middle jelly-like and bottom solid were separated. The middle layer was subsequently pressed, filtered and concentrated to constitute the molasses which were mixed with the previous liquid supernatant, supplemented with water (1:10 v/v) and allowed to further fermentation for 2 days. After fermentation, chicha was transferred to a narrow-mouth potsand ready for consumption. Yeast counts from different stages along the process showed an increase in colony counts from 102 in the initial stages to 106 in the first fermentative stage to decrease again in the following steps (102 cfu/ml) to the final increase after the second fermentation step (106 cfu/ml). A total of 523 colonies were isolated, identified and classified into thirteen yeast species belonging to nine genera. The distribution of yeast species showed Saccharomyces cerevisiae as the dominant species (73%) followed by Pichia sp. new. (8%), Candida parapsilosis (5.5%), Pichia membranaefaciens (4.4%) and Cryptococcus flavescens (3.8%). Yeasts are known to be involved in a range of functions in fermentations such as degradation of carbohydrates, production of aromatic compounds and oligosaccharides, stimulation of lactic acid bacteria, inhibition of mycotoxigenic moulds, degradation of cyanogenic glucosides and mycotoxins as well as probiotics. The high numbers of yeasts present along the fermentative process are likely to influence the nutritional and organoleptic characteristics of chicha.