Chemical Composition and Effect of Processing and Flour Particle Size on Physicochemical and Organoleptic Properties of Cocoyam (Colocasia esculenta var. esculenta) Flour
This work investigated the chemical composition of cocoyam corms and cormels and the effect of processing and particle size on the physicochemical and organoleptic properties of the flours for use as soup thickener. Fresh cocoyam corms and cormels were peeled, sliced, washed, divided into four parts that were variously blanched, sulphited and sulphited/blanched. The control was not treated. The slices were sun dried (32 ± 2oC, 3 days), milled and classified with standard sieves into particle sizes of 0.1, 0.2, 0.4, 0.6 mm. The flour samples and fresh corms and cormels were analyzed for the proximate composition, ascorbic acid, anthocyanin and oxalic acid contents. The flours were also analyzed for the pH, bulk density, water and oil absorption capacities and the sensory properties of colour and texture. On dry weight basis, the protein, fat, crude fibre, ash and carbohydrate contents of the corms, cormels and flours were the same (p > 0.05). Ascorbic acid, anthocyanin and oxalic acid contents were respectively reduced from averages of 30.35, 31.58 and 173.88 mg/ 100 g (dry weight) in the corm/cormel to ranges of 8.95 – 16.28, 9.58 – 15.90 and 141.69 – 160.68 mg/ 100 g in the flours. Bulk density was increased (p < 0.05) by blanching and particle size. The water and oil absorption capacities were increased (p < 0.05) by blanching. Colour preference was improved by sulphiting, blanching and decreasing particle size. Texture preference was only affected by particle size. Acceptablility of soups from flours were not affected by treatments and particle sizes.
Keywords: Cocoyam, blanching, sulphiting, particle-size, physicochemical properties.