Modeling And Process Optimization Of Parboiling Of Paddy Rice

Now a day’s parboiled rice has become popular in the world. This paper concentrate on finding arnmathematical model that describes the parboiling processes and selection of process time andrntemperature for adequate parboiling. For this purpose different mathematical models werernselected and fitted to the experimental moisture ratio of soaking and drying process. The bestrnmathematical models were selected based on maximum value of R2, and minimum value ofrnstandard error and mean square deviation. For the soaking process four mathematical modelsrnwere fitted to the experimental moisture ratio obtained by soaking the paddy at the temperaturernof 30, 40, 55 and 650C for 1, 2, 3 and four 4hr. After doing non linear regression with SPSS,rnHenderson and Pabis model gave the best result (with R2=0.997, standard error = 6.36×10-3 andrnmean square deviation =8.1×10-5). The coefficient of the Henderson and pabis model a and krnwere determined in terms of soaking temperature. The drying process takes place in two stagerndrying operation by fluidized bed and oven drying method respectively. The first stage dryingrnprocess carried out at a temperature of 40, 60, 80 and 1000C and relative humidity of 50, 35, 25rnand 15% at constant air velocity of 2.7m/s to reduce the moisture content from 37.25% to 19%rnwet basis. In the second stage of drying the moisture content were reduced from 19 to 11.32%rnwet basis at 450C. To select the best mathematical models that describe the drying process nonrnlinear regression were performed by SPSS on eight selected thin layer mathematical models. Thernregression result showed the Two Term parameter model gave maximum R2 (0.994) ,rnminimum standard error (0.02903038) and minimum mean square deviation (1.405×10-3) .Therndegree of gelatinization (x) during the steaming process were calculated from the absorbancernvalue by using amylose iodine method . The absorbance values were measured after the paddyrnsteamed at 70, 80, 90 and1000C for 12, 13.5, 15 and 16.5 min. The regression analysis ofrn−��������(1 − ����) against time showed a linear relationship with R2 of 0.968. This indicate that therngelatinization process follow a first order reaction. The rate constant of the gelatinization processrnwere calculated by using the degree of gelatinization. The activation energy of the gelatinizationrnprocess was 55.695KJ/mol. The selection of the parboiling process was carried out by thernminimum time require to soak, steam and the maximum value of head rice yield during therndrying process. Based on these criteria the time required to soak the paddy at 55°C was 5.13hrrnand the time require to steam the rice to gelatinize the up to completion (99.99999999%) atrn120°C was 62.2min. In the case of drying the optimum time and temperature were 40°Cand 20.989min in the fluidized bed drying and 45°C and 209.911min in the oven drying. Thernadvantage of parboiling over un parboiled rice were evaluated and it have better nutritionalrnvalue (calcium=365.54mg/kg, phosphorous=3594.75mg/kg, potassium=2503mg/kg andrncarbohydrate=79.68%), high head rice yield (72.48%), minimum solid loss (0.41%) duringrncooking, better sensory characteristics and good textural characteristics than un parboiled rice.rnThe parboiling process is feasible and has rate of return 27.37% and payback period of 2.35year.

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