Abstract

Fresh samples of soy-melon enriched and un-enriched (control) “gari” (afermented, dewatered and toasted granule from cassava) widely consumed all over West Africa and in Brazil, were prepared and used to determine their sorption isotherms. The sorption isotherms were determined within a range of water activities of (0.20 - 0.92) at three different temperatures of 20, 30 and 40^oC using the static gravimetric method. Results showed that the water sorption was temperature dependent as typical of food systems. The higher the temperature, the lower the equilibrium moisture content (EMC) at constant water activity (a_w). EMC for soy-melon “gari” ranged between 0.022 kgkg^-1 (db) and 0.320 kgkg^-1(db) within the temperature range of 20 and 40^oC; while those of un-enriched (control) “gari” ranged between 0.054 kgkg^-1(db) and 0.335 kgkg^-1(db). The GAB monolayer moisture values (M_o) were 0.044, 0.032 and 0.023 kgkg^-1(db) at 20, 30, and 40^oC respectively for soy-melon “gari”; while for the control “gari” samples, they were 0.080, 0.059, and 0.050 kgkg^-1 (db). The ‘Mean relative percent modulus’ (E%) values were 9.45, 7.37, and 9.61% at 20, 30 and 40^oC respectively for soy-melon “gari” samples; while for the control samples they were 3.76, 2.48, and 2.04%. The RSS values ranged from 0.0002 to 0.0008 for soy-melon gari while they ranged from 0.0001 to 0.0004 for the un-enriched gari at temperature between 20 and 40^oC. All the E% values were below 10%. These showed that there was perfect fitness between the experimental moisture sorption and the predicted GAB sorption. However, the values for un-enriched (control) “gari” samples were consistently lower than those of the enriched gari showing that GAB model could be used to predict the moisture equilibrium of control “gari” samples better than those of soy-melon “gari” at the range of water activities used in this study.

Key words: Soy-melon “gari”, supplementation, EMC, sorption isotherm.