CHEMICAL AND RHEOLOGICAL EVALUATION OF PRODUCTS FROM AFRICAN STAR APPLE (CHYROSOPHYLLUM ALBIDUM) PEELS AND COTYLEDONS.
The seeds and peels of African star apple (Chrysophyllum albidum) (“udara”) were split, followed by removal of mucilage from the seeds and subsequent cracking of the seed shells, and de-pulping of the peels. The seed cotyledons and peels were blanched at 1000C for 2,4 and 6 mins, wet milled with water in 1: 1.5 ratio, sieved with muslin cloth to obtain the extracts which were pasteurized at 800C for 10mins and stabilized with 0.2, 0.4, 0.6, 0.8 and 1.0 (g/litre) concentrations of carboxy methyl cellulose (CMC) and pectin each. A preliminary study was done on the African star apple (“udara”) peels and seeds by ranking to determine the best two stabilized samples from each of the three batches of 2, 4, and 6 mins blanched. Based on the overall acceptability of the panelists, six samples were selected for further study together with their respective controls making a total of twelve samples coded as follows: peel extract control samples A1, B1 and C1 of 2, 4 and 6 mins blanching respectively, cotyledon extract control samples A2, B2 and C2 of 2, 4 and 6mins blanching respectively, stabilized peel extract samples D1, E1 and F1 of 2, 4, and 6 mins blanching respectively, and stabilized cotyledon extract samples D2, E2 and F2 of 2, 4, and 6 mins blanching respectively. The fresh peel and cotyledon had moisture (22.36%), protein (1.68% and 4.33%), crude fibre (8.21% and 5.r99%), ash (0.18% and 0.30%), fat (0.50% and 3.05%) and carbohydrate (66.87% and 60.74%), respectively which reduced with increased blanching period. The antinutrients – tannin (0.400% and 0.240%), HCN (1.06% and 1.10%) and phytate (1.21% and 2.73%)- in both peels and cotyledons respectively also reduced appreciably with increased blanching period. Blanching considerably reduced the viscosity while stabilization increased the viscosity. Rheological characterization of “udara” peel and cotyledon samples was found to be shear thinning – pseudoplastic behaviour of non-Newtonian fluid. Freezing at -10°C of “udara” peel and cotyledon products caused significant (p<0.05) sedimentation of their solid fractions and subsequent separation into solids and water phases at all levels of stabilization.