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 5.99%), 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.