ABSTRACT

It has been found that Coco yams typically contains 20% - 28% starch; The Colocasia esculenta spp(taro) contains about 24.5%(Bradbury,1998). Some reports suggest taro starch granules are 5-6 sided polygons (Sefa-Dede et al,2002) and tend to be 0.08 – 0.25 µm. The smaller starch granules of coco yam have been associated with increased digestibility over other starchy crops. However, as a result of the unsuitability of starch in its natural/native state for industrial processes, it is often underutilized. This study is aimed at the exploration of starch modification; specifically, the modification of cocoyam starch using monochloroacetic acid. The method of chemical modification used in this work is called Carboxylmethylation which involves the substitution of hydroxyl groups in starch by adding the hydrophobic groups on the starch molecule. Carboxylmethylation is known to improve the physiochemical and morphological properties of native starch. The Carboxymethyl starch was prepared using varied ratios of cocoyam starch and monochloroacetic acid. The result of modification of Carboxylmethyl cocoyam starch carried out in this project using varying starch to monochloroacetic acid ratios showed variations in the degree of substitution of 0.1248,0.1872,0.1325,0.4942 to the modified cocoyam starch of ratios 4:1,1:5:1,1:1:5,1:4 respectively. Certain reports suggest that the determining factor for the method of starch modification to be used depends on the desired end product (Zhang,2017). In this case of carboxymethylation of cocoyam starch, from the results obtained, it can inferred that to get a highly substituted cocoyam starch, the starch to monochloroacetic acid ratio of 1:4 should be used to carry out the reaction but if the desired end product is a cold-water soluble starch, then starch to monochloroacetic acid ratio of 4:1 is best.