Effect of mash quantity and roasting duration on some physical and pasting properties of gari

Central composite rotatable of response surface methodology experimental design was used to determine effect of mash quantity and roasting duration on physical, pasting and sensory properties of gari. Five levels of quantity (317, 400, 600, 800 and 882.2 g) and roasting time (37.1, 35, 40, 45 and 47.1 min) were used at a fixed roasting temperature (95°C). The responses were moisture, pH, bulk density, water absorption capacity, swelling index, and peak, trough, breakdown, final and setback viscosities, peak time, pasting temperature and acceptability of the products. Moisture content, pH, bulk density, water absorption capacity and swelling index of the samples were (11.1 – 18.8 %), (2.4 -3.4), (1.02 – 1.11 g/cm³), (2.0 – 5.4 ml/g) and (2.4 – 3.4 ml/ml) respectively. Among the physical properties determined, only bulk density was not significantly (p 0.05) affected. Peak and break down viscosities were not significantly (p 0.05) affected, while other pasting properties studied (trough, final viscosity, set back viscosity, peak time and pasting temperature) were significantly (p 0 .05) affected by mash quantity and roasting duration. Recorded mean were peak 1907.58 ± 983.3 RVU, trough 1987.42 ± 501.89 RVU, break 228.15 ± 280.43 RVU, final 3827.46 ± 735.51 RVU, set back 1840.04 ± 419.75 RVU, peak time 6.38 ± 0.66 min and pasting temperature 54.02 ± 3.82°C. All samples roasted for more than 35 min were poorly rated.