Storage Stability of Unstabilized Predigested Soymilk Fortified with Micronutrients – A Response Surface Approach

Abstract

Soymilk prepared from TGX 923-2E soybean variety previously soaked for 12 h and sprouted for 72 h was fortified with ferric ammonium citrate (Fe), calcium carbonate (Ca) and vitamin C (VC) according to Box-Wilson (1951) experimental design matrix at 5 level combinations. A central composite rotatable response surface (CCRRS) was employed to study the linear, quadratic and cross product effects of the micronutrient fortification on storage stability of some selected soymilk physico-chemical properties stored for 12 weeks. A total of 21 experimental runs were generated and the response surface data for each run was statistically regressed and analyzed for variance using Minitab computer software (version 11.21). Results obtained showed that dietary iron had linear significant (P < 0.05) effect to increase visible coagulation time (VCT), colour and dietary iron content. Calcium carbonate (CaCO₃) had the strongest positive linear significant (P < 0.05) effects on total solids, ash, pH, viscosity, calcium content, and strongest negative significant (P < 0.05) effects on visible coagulation time (VCT) of the fortified soymilk. Vitamin C had linear significant (p < 0.05) effects to increase soymilk vitamin C content and VCT.

Keywords: Storage stability, micronutrient fortification, predigested soymilk, complementary feeding and response surface methodology