Physico-thermal and pasting properties of soy-melon-enriched “gari” semolina from cassava

Abstract

The physical, thermal and pasting properties of “gari”, a fermented and toasted cassava granule, enriched with 10% full fat soy-melon protein supplements, at different processing stages, were studied. The stages at which the gari meal was enriched were: after fermentation but before toasting (PRT, soak-mix method) and after toasting (AFT, dry-mix method). Based on the result of the analysis of the physical properties, the swelling index of the samples decreased from 3.79 for the control sample to a range of 3.15-3.34 for the enriched samples. Wettability values increased from 49 s for the control sample to about 135-148 s for the enriched gari. A decrease in porosity from 42% for the control sample to 29.33%-32.33% for the enriched samples relative to their moisture contents was observed in the enriched samples. Enriched “gari” sample of minimum average particle size (AFT) have the highest angle of repose of 37° while the control sample of maximum average particle size have the lowest angle of repose of 29°. There was an increase in the degree of penetration by cone penetrometer from 19 mm for the control sample to a range of 22.43-23.90 mm for the enriched samples indicating higher gel strength for the control sample. On the basis of the thermal properties, there was increase in swelling power and the solubility of all the samples with increase in temperature. The control “gari” had significantly higher swelling power in a range of 5.17-6.68 g/g compared to that of the enriched samples (4.61-5.27 g/g) between the temperature of 45 and 90°C. The control sample exhibited higher specific heat capacity of 1.222 kJ/(kg · K) than the enriched samples that ranged between 1.085- 1.118 kJ/(kg·K). On the basis of the pasting properties, the control sample had the highest viscosity of 300.92 RVU while the enriched samples had lower viscositiy. The enriched samples formed paste at lower temperature 79.20-80.05°C and took shorter time 3.93-4.07 min to gelatinize. The enriched “gari” sample exhibited high setback and breakdown viscosity values of indicating that its paste will have lower stability against retrogradation than the UN-enriched gari samples.