Central composite mixture design was employed in the formulation of composite blends, numerical optimization of the protein, carbohydrate, texture, appearance, taste and overall acceptability score of the instant dried noodles prepared with rice flour (RF), soybean flour (SF), corn starch (CS) and potato starch (PS). Rice flour (X1, 70–85%), soy flour (X2, 5–15%), corn starch (X3, 5–15%) and potato starch (X4, 5–12%) were the independent variables investigated with respect to six response variables including protein (Y1), carbohydrate (Y2), texture (Y3), appearance (Y4), taste (Y5) and overall acceptability (Y6). In all 20 experiments were conducted by I-optimal mixture design keeping the upper and lower values of ingredients above in range. Instant dried rice-soy noodles were developed. Regression analysis of all the analyzed responses showed R2>0.75, predicted R2 and adjusted R2 were in reasonable agreement. With correlation coefficients of -0.912, -0.841, -0.843, -0.844 and -0.829, for carbohydrate content, texture, appearance, taste and overall acceptability respectively, soybean flour demonstrated a negative association with rice soy noodles. Whereas, soybean flour had a significant (p<0.05) impact on the crude protein. Additionally, the 3D surface plot revealed that an increase in soybean flour setting resulted in an increase in protein content and a decrease in the values for carbohydrates, textural appearance, and overall acceptability. Numerical optimization was conducted on the basis of research objectives. Protein and carbohydrate content were maximized with the lower and upper values of 10-12 and 65-75 respectively, while texture, appearance and overall acceptability were set in range with the values of 7.5-8.5. Four optimum solutions were selected with blend ratio of 70:13.13:11.75:5.12 (sample A), 73.297:11.664:5.082:9.956 (sample B), 72.995:11.585:5.199:10.222 (sample C) and 72.198:11.283:5.498:11.020 (sample D) for RF:SF:CS:PS with corresponding desirability ratings of 0.904, 0.894, 0.891 and 0.842 which resulted in the predicted value of 12.827 and 78.271% for protein and carbohydrate while texture, appearance, taste and overall acceptability score were 7 (like moderately), 8.5 (like very much), 8.0 (like very much) and 8 (like very much) respectively.
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