Abstract
The effect of defoliation on mineral and food value of two cassava varieties defoliated at varying phenological phases was studied to ascertain the appropriate phenological phase when harvested leaves would contain the optimum mineral and proximate composition, gross energy and the least cyanide content. Two cassava cultivars were subjected to defoliation at varying phenological stages including logarithmic, vegetative and physiological maturity phases. The mineral content was highest at the logarithmic phase than any other phases. The proximate composition of the cassava leaves showed that crude protein was highest at physiological maturity, while the least HCN was observed in cassava defoliated at logarithmic phase. Analysis of mineral and proximate content showed that leaf of the ‘TMS30572’ cultivar had the highest mineral content, fat, fibre, ash, dry matter and gross energy at the logarithm phase while ‘OkoIyawo’ had the highest crude protein and HCN at physiological maturity. This study indicates the high potential of cassava leaf as an unconventional source of protein for both humans and animals when defoliated at logarithmic growth phase.
Highlights
Tender leaves of cassava which could be harvested periodically throughout the growing season are utilized in some areas as relish, during the dry season, when there are few leafy vegetables (IITA, 1990)
Exploitation of the food value of this crop is greatly masked by the endogenous presence of cyanogenic glucosides
This study provides analytical information on the mineral content, proximate composition, hydrogen cyanide and metabolizable energy values of cassava leaf of commonly grown local and improved cultivar defoliated at varying phenological growth phases in derived savanna agro-ecology
Summary
Tender leaves of cassava which could be harvested periodically throughout the growing season are utilized in some areas as relish, during the dry season, when there are few leafy vegetables (IITA, 1990). Leaf harvesting involves plucking the fully expanded tender leaves and the same field can be visited frequently if it is the only available cassava field. Exploitation of the food value of this crop is greatly masked by the endogenous presence of cyanogenic glucosides. These glucosides, typified by linamarin [2-(αDglucopyranosyloxy) isobutyronitrile] and lotaustralin [2- (α- D glucopyranosyloxy) methylbutyronitrile] are hydrolyzed to hydrocyanic acid (HCN) by endogenous linamarase These glucosides, typified by linamarin [2-(αDglucopyranosyloxy) isobutyronitrile] and lotaustralin [2- (α- D glucopyranosyloxy) methylbutyronitrile] are hydrolyzed to hydrocyanic acid (HCN) by endogenous linamarase (EC. 3.1.1.21, linamarin, α-D-glucoside glucohydrolase) when cassava tissues are disrupted by cutting, grating, bruising or other mechanical means (Conn, 1969; Bradbury et al, 1991)
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