Study of Mechanical, Physico-Chemical and Sensory Properties of Products From Four Cassava Varieties

Abstract

Four varieties of cassava, namely: 91/02324, 97/4779, 98/2101 and NR87184 were processed into chips (30 x 2.0 x3.0 mm), ‘abacha shreds (0.80, 1.0, 1.6 mm thick) ‘abacha’ slices (0.5 mm x 60 mm) and gari. Part of the chips was processed into ‘abacha’ slices and gari to compare the products with those made from fresh roots. The mechanical properties of the products, the hydration kinetics of the chips and the ‘abacha’ shreds as well as the chemical, functional, rheological and sensory properties of the products were studied. The results show that gari from chips and fresh cassava roots were comparable in quality in terms of chemical and rheological properties although gari from dried chips was rated low in sensory attributes. The pasting properties of gari from fresh cassava roots were significantly (p<0.05) higher than those made from dried chips. The peak viscosity of gari made from 91/02324 was the highest recorded, while the final viscosity and the trough viscosity of the product made from 98/2101 were the highest. Cassava variety 97/4779 produced gari with the highest gel consistency when reconstituted at gari: water ratio of 1:4 (w/v) when the water was heated to 100 0C, while at water temperature of 80 0C it produced dough with significantly (p<0.05) higher gel strength (harder texture) at different volumes of water. Cassava variety NR87184 produced the least gel strength (soft dough) at a water temperature of 100 0C. Generally, gari dough was found to undergo a thinning effect with increase in water temperature and volume. The rate of moisture uptake and the time in while the chips attained equilibrium moisture content varied with soaking temperature and cassava variety. High coefficients of determination (r2 =0.9656-1.000) obtained correlating the experimental and predicted moisture uptake values for chips show that the Peleg’s equation can be used to model water uptake of cassava chips from all four varieties. The position (vertical/horizontal orientation) of the chips as well as the cassava varieties from which they were made affected the mechanical properties of the chips significantly (p<0.05). For single-stranded ‘abacha shreds and gari dough, the mechanical properties at the yield point differed significantly (p<0.05) from that at peak value. Production of ‘abacha’ slices using dried cassava chips significantly (p<0.05) lowered consumer acceptance of the product. Cassava variety 97/4779 produced the most acceptable product in terms of chemical and sensory properties. When 97/4779 was studied more concertedly for ‘abacha’ slice production, boiling, peeling and slicing produced the most acceptable ‘abacha’ slices. Boiling 97/4779 for 30 minutes and soaking for 16 hours produced ‘abacha with the highest protein (1.337%), while boiling for 30 minutes and soaking for 20 minutes produced ‘abacha’ with the highest fibre content of 1.49%. The least value of HCN (4.596mg/kg) was obtained when boiling time and soaking time were 75 minutes and 8 hours, respectively. Boiling affected the carbohydrate, ash, protein, fat and fibre contents of ‘abacha’ slices, while soaking time significantly (p<0.05) affected the protein, fat and fibre contents of ‘abacha’ slices made from 97/4779. The pasting properties of flour made from ‘abacha’ slices processed from fresh and dried chips of 91/02324 were higher than those made from other varieties. Its high peak viscosity of 399.54 RVU indicates its suitability for products that require high gel strength and high elasticity. ‘Abacha’ shreds of thickness 1.0mm produced the longest strands. However, consumers preferred ‘abacha’ shreds of thickness 0.8mm as meal and snacks. Variety 97/4779 and 98/2101 were most preferred for making ‘abacha’ shreds.