Microbiological and biochemical characterization of cassava retting, a traditional lactic Acid fermentation for foo-foo (cassava flour) production

Abstract

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 2 to C 4) 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. MATERIALS AND METHODS Origin of the plant material. Cassava roots (Manihot esculenta var. MM86) were harvested near Brazzaville, Congo, 15 months after planting. Retting procedures. Approximatively 100 kg of roots was washed, peeled, and placed in a 200-liter barrel filled with rainwater, which was left at ambient temperature. This retting procedure was repeated four times, always yielding similar results; the data presented are from a single representative retting. Sample preparation for bacterial enumeration. Sampling was performed every 12 h for the first 2 days and then daily until retting was completed. Six randomly selected root sections were cut into 0.5-cm-diameter cubes and mixed under sterile conditions. A 60-g sample was diluted in 540 ml of sterile peptonized water reduced by boiling and addition of cysteine-HCl (0.1% [wt/vol]); this corresponded to a 10 Ϫ1 dilution. The solution was then mixed in a blender (Turnmix ME 88; SOFRACA,

Development of starter culture for improved processing of Lafun, an African fermented cassava food product

“…Spontaneous cassava fermentations for Lafun production are usually associated with the softening of the submerged root (Oyewole and Odunfa 1988;Padonou et al 2009b). This phenomenon has been observed in other cassavabased fermentations such as Foo-Foo (Okafor et al 1984;Ampe and Brauman 1995;Brauman et al 1996) and Agbelima (Amoa-Awua et al 1996). Different groups of micro-organisms have been assumed to contribute to the softening of the root.…”

“…The degree of root softening is the most important criterion to determine the end of Lafun fermentation (Oyewole and Odunfa 1988;Padonou et al 2009b). In this respect, the activities of pectinolytic enzymes such as pectin methylesterase and pectate lyase have been reported to occur during cassava fermentation Brauman et al 1996). These enzymes originate from micro-organisms associated with the fermentation process (Okafor et al 1984;Ampe and Brauman 1995).…”

The linamarase ofMucor circinelloidesLU M40 and its detoxifying activity on cassava

“…as aspartate or glutamate, is involved in catalysis (Flores et al 1992). Mucor circinelloides linamarase was stable under a wide pH range (3·0-7·0), suggesting a possible utilization in detoxification processes based on lactic fermentation (Okafor 1977;Amoa-Awua et al 1996;Brauman et al 1996). Most linamarases from autochthonous cassava fermentation bacteria (Okafor and Ejiofor 1985), as well as the cassava b-glucosidase itself (Eksittikul and Chulavatnatol 1988;Nok and Ikediobi 1990), however, do not show the same stability to acid pH.…”

Isolation, characterization and identification of lactic acid bacteria and yeasts from sourMifen, a traditional fermented rice noodle from China

“…Lact. plantarum has been identified as the dominant micro-organism at the end of several natural lactic acid fermentations (Brauman et al 1996;Kunene et al 2000), probably because of its acid tolerance (Fleming and McFeters 1981;Hounhouigan et al 1993;Steinkraus 1997) and its superior ability to utilize the substrates (Oyewole and Odunfa 1990), including dextrins (Akinrele 1970). Some of the Lact.…”