Identification of the predominant microbiota during production of lait caillé, a spontaneously fermented milk product made in Burkina Faso

Abstract

The spontaneously fermented curdled milk product from Burkina Faso, lait caillé is prepared by traditional processing from raw unpasteurised milk. The fermentation lasts 1-3 days. This study aims to identify the predominant microbiota involved in lait caillé fermentation from cow milk. A survey on lait caillé end-products from local markets showed pH ranges of 3.5 to 4.2. Counts of total lactic acid bacteria (LAB) were 7.8 ± 0.06 to 10.0 ± 0.03 log CFU/g and yeast counts were 5.3 ± 0.06 to 8.7 ± 0.01 log CFU/g, together with considerate amounts of Enterobacteriaceae < 3.00 to 8.4 ± 0.14 log CFU/g. Sampling throughout the entire fermentation of lait caillé was performed at a traditional house-hold production site. A drop in pH from 6.7 ± 0.01 at 0 h to 4.3 ± 0.08 in the end-product (59 h) was found. Total LAB counts increased to 8.6 ± 0.02 log CFU/g in the end-product, while yeast and Enterobacteriaceae counts reached 6.4 ± 0.11 and 6.7 ± 0.00 log CFU/g, respectively. LAB and yeasts isolated during the fermentation were clustered by (GTG)₅ repetitive-PCR fingerprinting followed by 16S and 26S rRNA gene sequencing, respectively. Microbial successions were observed with Leuconostoc mesenteroides being the predominant LAB followed by Pediococcus pentosaceus and Weissella paramesenteroides at the onset, while Lactococcus lactis and Enterococcus spp. where the predominant LAB after 7 h of fermentation. During the first 18 h Candida parapsilosis was the dominant yeast species, while from 35 h to the end-product, Saccharomyces cerevisiae predominated. The microbial safety risk pointed out in this study, showed the need for implementation of good manufacturing practices including pasteurisation and use of well-defined starter cultures.

Keywords: Fermented milk products; Food safety; Lactic acid bacteria; Lait caillé; Yeasts.