Modelling temperature and slice thickness effect on b-carotene, carbohydrate and moisture contents of orange-fleshed sweet potato flour
Abstract
In this study, the effect of oven temperature (OT) and slice thickness (ST) of orange-fleshed sweet potato (OFSP) on Beta-carotene, carbohydrate, and moisture contents of OFSP flour was determined. A 22 full factorial experimental design with two replications was used. The washed, peeled and sliced OFSP roots were dried to constant weights in an oven. The dried slices were milled into flour using a grinder and then sieved using a 200 µm sieve to achieve particle size uniformity. The colour parameters, carbohydrate, and moisture contents of the resultant flour were determined. Statistical analyses were done using Design Expert 12 software at (p < 0.05) significance level. Results showed that OT had significantly negative effect while ST had significantly positive effect on the pigments, carbohydrate, and moisture contents of OFSP flour. Both OT and ST, however, had significantly positive interaction effect on the dependent variables. At the design points and their proximities, the following linear equations were found to be adequate: B-carotene (b*) = 82.47 - 1.06 * OT - 1.25 * ST + 0.03 * OT * ST; Carbohydrate = 103.87 - 0.55 * OT - 1.27 * ST + 0.02 * OT * ST; Moisture content = 13.87 - 0.07 * OT - 0.11 * ST. However, at the centres of the design space, the linear equations were found inadequate for predictions, which indicated the need for further studies on quadratic or cubic model development. The results mean that 10 mm thick slices oven-dried at 85o C would give properly dried (9.4% M.C.) high-protein (6.7%) flour; while 10 mm thick slices dried at 45o C would give high carbohydrate (76%) flour with good colour retention.
In this study, the effect of oven temperature (OT) and slice thickness (ST) of orange-fleshed sweet potato (OFSP) on Beta-carotene, carbohydrate, and moisture contents of OFSP flour was determined. A 22 full factorial experimental design with two replications was used. The washed, peeled and sliced OFSP roots were dried to constant weights in an oven. The dried slices were milled into flour using a grinder and then sieved using a 200 µm sieve to achieve particle size uniformity. The colour parameters, carbohydrate, and moisture contents of the resultant flour were determined. Statistical analyses were done using Design Expert 12 software at (p < 0.05) significance level. Results showed that OT had significantly negative effect while ST had significantly positive effect on the pigments, carbohydrate, and moisture contents of OFSP flour. Both OT and ST, however, had significantly positive interaction effect on the dependent variables. At the design points and their proximities, the following linear equations were found to be adequate: B-carotene (b*) = 82.47 - 1.06 * OT - 1.25 * ST + 0.03 * OT * ST; Carbohydrate = 103.87 - 0.55 * OT - 1.27 * ST + 0.02 * OT * ST; Moisture content = 13.87 - 0.07 * OT - 0.11 * ST. However, at the centres of the design space, the linear equations were found inadequate for predictions, which indicated the need for further studies on quadratic or cubic model development. The results mean that 10 mm thick slices oven-dried at 85o C would give properly dried (9.4% M.C.) high-protein (6.7%) flour; while 10 mm thick slices dried at 45o C would give high carbohydrate (76%) flour with good colour retention.
