Optimization and Evaluation of Soy-Tiger Nut Milk as Beverage

The study produced milk drink that is high in protein and energy from soy beans and tiger nuts blends as well as to assess the beverage qualitatively and customer acceptability using response surface methodology (RSM). The principal raw materials used were soybeans and tiger nut. They were processed into milk at different formulations without using chemical preservative. Sensory evaluation, pH, titratable acidity as well as proximate and mineral compositions were determined. The results showed that the minimum and maximum colour score varied from 4.4 to 5.0. The quadratic model for colour was found to be significant (p<0.05) in tiger nut inclusion. The model equation obtained for colour = 4.50 + 0.048*A + 0.098*B + 0.019*A2 + 0.12*B2 + 0.18*A*B where A = Soybeans, B = Tiger nut. Mouth feel model’s F-value of 7.35 indicates that it was significant (p<0.05). Model terms are considered important when the “Probability > F” value was less than 0.05. The model for quadratic equation for mouth feel was 7.290. +5.00 -0.091*A -0.19*B -0.14* A2 -0.44* B2 +0.45* A*B. The model for the quadratic equation for Taste = +3.90 +0.030*A +0.020* B +0.21*A2 +0.056*B2 +0.075*A*B adequate precision = 3.65, corrected R2 = 0.29, R2 = 0.59 and the predicted R2 = -1.94. It was observed the pH values decreases with storage days from day 0 to day 8 for samples A, I and Z.  On day 12, the pH values increased for all the samples except for sample M.  The Titratable acid increased as the pH decreased. On the 0 day, sample A had value of 20.8 while sample M was 23.33. However, sample I increased from 0, 4, 8 and 12 days (20.19, 20.20, 22.47 and 23.73) respectively. Sample M had the highest protein content (3.52%), followed by sample A (3.21%), sample I (3.01%) and sample Z (2.02%). Sample Z had the lowest fiber content (0.30%), next was sample I (O.43 %), sample A (0.51%), and sample M (0.54%). The range of moisture contents was 81.03 to 82.04%.  Conclusively, optimizing soybeans at 100g/ml with 40 g/ml of tiger nut could help to improve the sensory attributes such as colour, taste, mouth feel, flavor and overall acceptance. The formulation could influence shelf stability of product, bridge protein in-balance and reduction in malnutrition level.