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Appl. Environ. Microbiol., Aug 1996, 2854-2858, Vol 62, No. 8
A Brauman, S Keleke, M Malonga, E Miambi and F Ampe
The overall kinetics of retting, a spontaneous fermentation of cassava
roots performed in central Africa, was investigated in terms of
microbial-population evolution and biochemical and physicochemical
parameters. During the traditional process, endogenous cyanogens were
almost totally degraded, plant cell walls were lysed by the simultaneous
action of pectin methylesterase and pectate lyase, and organic acids
(C(inf2) to C(inf4)) were produced. Most microorganisms identified were
found to be facultative anaerobes which used the sugars (sucrose, glucose,
and fructose) present in the roots as carbon sources. After 24 h of
retting, the fermentation reached an equilibrium that was reproducible in
all the spontaneous fermentations studied. Lactic acid bacteria were
largely predominant (over 99% of the total flora after 48 h) and governed
the fermentation. The epiphytic flora was first replaced by Lactococcus
lactis, then by Leuconostoc mesenteroides, and finally, at the end of the
process, by Lactobacillus plantarum. These organisms produced ethanol and
high concentrations of lactate, which strongly acidified the retting juice.
In addition, the rapid decrease in partial oxygen pressure rendered the
process anaerobic. Strict anaerobes, such as Clostridium spp., developed
and produced the volatile fatty acids (mainly butyrate) responsible,
together with lactate, for the typical flavor of retted cassava. Yeasts
(mostly Candida spp.) did not seem to play a significant role in the
process, but their increasing numbers in the last stage of the process
might influence the flavor and the preservation of the end products.
Copyright © 1996, American Society for Microbiology
Microbiological and Biochemical Characterization of Cassava Retting, a Traditional Lactic Acid Fermentation for Foo-Foo (Cassava Flour) Production
Laboratoire de Microbiologie et de Biotechnologie, Institut Francais de Recherche Scientifique pour le Developpement en Cooperation (ORSTOM), Centre ORSTOM, BP 181, Brazzaville, Congo
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