Response surface optimization of thermo-sonication conditions and taro mucilage concentrations for the preparation of soy yogurt

The present study embarked on developing soy yogurt utilizing soybean and taro mucilage. Box-Behnken Design (BBD) of Response Surface Methodology (RSM) was executed to optimize the ingredient and thermo-sonication conditions such as temperature (A: 40–60 °C), time (B: 5–15 min), and mucilage concentrations (0.1–0.3 g/100 mL) on the responses such as pH, acidity, syneresis, water holding capacity, viscosity, texture profile (firmness, adhesiveness, gumminess), and overall acceptability. The analyses showed that the soy yogurts have a titratable acidity (0.73 ± 0.43 % - 0.85 ± 0.58 %), pH (4.7 ± 0.40–4.93 ± 0.68), total soluble solid (26 ± 3.2 °Brix - 42.2 ± 4 °Brix), syneresis (26 ± 3.2 % - 39.98 ± 3.7 %), water holding capacity (36.33 ± 4.91 % - 55.7 ± 2.27 %), viscosity (1367.3 ± 2.98 mPa s - 2306.13 ± 3.21 mPa s), whitening index (76.1 ± 3.22–82.33 ± 2.18), firmness (14 ± 5 g - 26 ± 2 g), cohesiveness (13 ± 3.74 g s - 23.2 ± 2.88 g s), gumminess (0.7 ± 0.01 g - 1.8 ± 0.03 g), and overall acceptability (3.96 ± 0.16–4.54 ± 0.32). From the variance analysis, the R2 of eleven response variables is more than 0.85, which indicates the model explained a high proportion of variability. At 60 °C thermo-sonication temperature, 13 min thermo-sonication time, and 0.3 g/100 mL mucilage concentration, the optimal conditions recorded for 0.780 ± 0.21 % (titratable acidity), 4.701 ± 0.51 (pH), 10.986 ± 0.76 °Brix (total soluble solid), 27.886 ± 0.49 % (syneresis), 54.687 ± 0.38 % (water holding capacity), 1810.541 ± 5.75 mPa s (viscosity), 23.126 ± 0.45 (firmness), 16.945 ± 0.21 (cohesiveness), 1.485 ± 0.48 (gumminess), 81.764 ± 0.32 (whitening index), and 4.365 ± 0.42 (overall acceptability). Furthermore, the developed models' actual response and predicted values correlated with each other as the Residual Standard Error (RSE) values were ≤5 %. This suggests that our model can reliably guide the selection of optimal parameters for any combination of factors. Ultimately, the insights garnered from this study hold promise for the large-scale production of taro mucilage-based soy yogurt, offering a versatile and nutritious addition to the repertoire of dairy alternatives.