Isolation and physico-chemical characterization of cola starch.

摘要

Cola nitida (Vent).Schott & Endl, a tropical dicotyledonous tree (family- malvaceae and sub-family – stercullioideae), is a well known plant in the sub-Saharan Africa and renowned for its socio-economic importance in Nigeria and other parts of West Africa. The plant was examined for the nut’s starch composition and its physicochemical properties compared with corn starch. The starch was isolated using 1 % w/v sodium metabisulphite and the proximate analysis (in %) was found to be 4.60 protein, 0.54 crude fibre, 0.54 fat, 1.06 ash, 67.57 total starch and 10.42 moisture. The starch percentage solubility was 7.48 % with a swelling capacity of 8.85 % and an amylose/amylopectin content of 24:76. It has a pasting temperature of 74.5 oC, gelatinization temperature of 74 oC hydration capacity of 88.59 %, emulsion and foam capacities of 5.22 % and 1.87 % respectively. The Rapid Visco Analysis (RVA) of the cola starch has a peak viscosity of 314.42 RVU and the results of the Differential Scanning Calorimetry (DSC) showed peak temperature of 321 oC and onset temperature of 300.7 oC. The photomicrograph indicates that the starch granule is oval in shape, generally small sized with occasional large ones, loose granules with no aggregation and had a mean particle size distribution of 15.33 % at 710 μm. The mineral content composition gave: iron 0.263mg/100g; phosphorus 67.43mg/100g; potassium 4.36mg/100g; calcium 9.40mg/100g; zinc 0.48mg/100g; magnesium 3.78mg/100g; copper (trace), and sodium 1.55mg/100g. Generally, the values obtained for the physicochemical and functional properties compared favorably with that of corn starch, and suggest that cola starch in the unmodified form can be used as a gelling agent, a fat replacer in the food industries where low fat is required and in the manufacture of noodles. It however cannot be used as an emulsifier as a result of its low emulsion and foam capacities. Key words: Cola, starch, isolation, composition, properties