Effect of foaming agent, foam stabilizer and whipping time on drying process of tomato paste under different drying equipment

摘要

Laboratory experiments were conducted to determine the effect of foaming agent (egg white (EW)), foam stabilizer (carboxyl methyl cellulose (CMC)) and whipping time on drying rate and quality of tomato (Lycopersicon esculentus) paste dried under air oven, microwave oven and mechanical dryer. A 43 factorial experiment in Randomized Complete Block Design (RCBD) was used to study the effect of four levels each of foaming agent (5%, 10%, 15% and 20%EW), foam stabilizer (0.15%, 0.30%, 0.45% and 0.60%CMC) and whipping time (3, 5, 7 and 9min) on the drying rate and the quality of foam-mat dried tomato powder in the three drying equipment. Each trial was performed in triplicates making a total number of 576 samples that were individually tested and measured. 25 g sample of the paste was dried to a moisture content of 7.60% (wb) for 8h in mechanical dryer and oven dryer at temperatures of 55°C and 50°C, respectively, and 10 min in microwave oven at 540 W. Data obtained from the experiments were statistically analyzed using the analysis of variance (ANOVA) while the Duncan's Multiple Range Test was used to compare the means. Results showed that the drying rate increased with increase in foaming agent, foam stabilizer and whipping with minimum values of 9.21 g/h obtained in mechanical dryer, 9.31 g/h in air oven and 8.05 g/h in microwave oven. Increase in foaming agent, foam stabilizer and whipping time did not cause any adverse effect on vitamin C, ash, protein, fat, carbohydrate, crude fiber contents of the samples. Samples reached a stable moisture content of 7.60% (wb) in less than 8 h in mechanical dryer and air and less than 10 min in microwave oven. The results of the study showed that EW, CMC and whipping time influenced the drying rate and quality of foam-mat dried tomato powder.