Characterisation of the microflora of attiéké, a fermented cassava product, during traditional small-scale preparation

Abstract

Attiéké is a fermented cassava product consumed mainly in Cote d'Ivoire. The aim of this study was to characterise the attiéké fermentation by examining products from 15 small-scale production sites at various stages of its preparation. For the preparation of attiéké, fresh cassava is grated to a pulp and inoculated with 10% of a spontaneous traditional inoculum. The inocula contained aerobic mesophiles at mean numbers of 8.2 × 10 7 cfu/g and lactic and acetic acids at mean concentrations of 0.2% and 0.1%, respectively. The mean pH was 5.0. Lactic acid bacteria were the dominant microorganisms in cassava pulp throughout fermentation with the mean numbers being 1.2 × 10 9 cfu/g after 15 h. The identification to the species level of microorganisms from one representative attiéké production of good quality showed that, at the start of fermentation, Leuconostoc mesenteroides subsp. mesenteroides was present in the highest numbers, accounting for 20% of all lactic acid bacteria. As the fermentation proceeded, this species was replaced by homofermentative lactic acid bacteria, Lactobacillus salivarius and Lactobacillus delbrueckii subsp. delbrueckii, present at 20% and 16%, respectively, and obligate heterofermentatives, Lactobacillus fermentum and Lactobacillus confusus at 12% and 10%, respectively, of total lactic acid bacteria in the flora at the end of fermentation. High numbers of acid-sensitive microorganisms, Bacillus circulans, Bacillus lentus, Enterobacter sakazakii, Enterobacter cloacae and Klebsiella pneumoniae subsp . pneumoniae, were transferred to the pulp in the inocula, but acidification to a mean pH of 4.4 with mean lactic and acetic acid concentrations of 0.59% and 0.2%, respectively, prevented their growth and reduced their numbers to less than 10 2 cfu/g at the end of fermentation. The mean numbers of Candida tropicalis, the main yeast present, remained relatively constant at about 10 5 cfu/g throughout attiéké production. The mean numbers of aerobic mesophiles decreased to below 10 2 cfu/g as a result of the steaming process. The finished attiéké had a mean pH of 4.4 and mean lactic and acetic acid concentrations of 0.6% and 0.1%, respectively.