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A Study of Heap Fermentation Process of Cassava Roots in Nampula Province, Mozambique

2007; Volume: 33; Issue: 2 Linguagem: Inglês

0378-2409

Lucas Daniel Tivana, J. M. Bvochora, Anthony N. Mutukumira, John David Owen,

Isotope Analysis in Ecology

Cassava (Manihot esculenta Crantz), a tropical root crop, is an essential part of the diet of the inhabitants of Nampula Province in Northern Mozambique. The heap fermentation process was followed in the households and samples of cassava roots collected from Nacaroa district, Nampula Province. Some biochemical and microbial changes occurring during the heap fermentation of cassava roots were determined and predominant micro-organisms were isolated and identified. The total crude protein and cyanogenic content were determined in dried fermented and unfermented cassava flour. Laboratory simulation of the heap fermentation of cassava roots using two isolated moulds was carried out to determine the mould growth rate and changes in the texture of different sliced cassava roots. In the field study, the heap fermentation took 4 to 5 days. The moulds, Rhizopus stolonifer and Neurospora sitophila were the dominant microbes involved in the heap fermentation of cassava followed by lactic acid bacteria, Leuconostoc pseudomesenteroides, Leuconostoc mesenteroides, Enterococcus faecium and Weissella cibaria. The pH of the cassava roots decreased from 6.1 + 0.01 to 5.6 + 0.6 during heap fermentation. Heap fermentation of cassava resulted in a decrease in the total cyanogenic content. The average total cyanogenic level in unfermented cassava flour was 158 mg HCN kg-1, while in fermented cassava flour, a value of 17 mg HCN kg-1 was recorded. The average cyanogenic content of fresh cassava roots was 258.9 + 8.7 mg HCN kg-1. Protein content in the cassava flour slightly increased from 1.3 % to 1.8 % w/w dry matter during fermentation. Slicing the cassava roots increased the rate of mould growth and the softness of the roots making faster the fermentation.