Effects of micronutrient fortification on moisture content, total solids, and general acceptability of soy milk extracted from sprouted soybeans – a response surface approach

Abstract

Effects of micronutrient fortification on moisture content, total solids and general acceptability of soy milk extracted from 12 h tap water steeped and 72 h sprouted TGX 923-2E soybean variety were evaluated. The soy milk was fortified according to Box-Wilson (1951) experimental design matrix with ferric ammonium citrate (Fe), calcium carbonate (Ca) and vitamin C (VC) as fortificants. Central composite design (k = 3) was used to develop a prediction model to investigate the effects of these fortificants. Data on each run were statistically regressed with Minitab (version 11.21) and Matlab (version R2007b) computer software to generate respective estimate regression coefficients to develop prediction equation and response surface plots to visualize the effects. Regression models showed that calcium carbonate had negative linear significant (P ≤ 0.05) effect and positive linear significant effect on soy milk moisture content and total solids, respectively. Ferric ammonium citrate had negative linear significant (P ≤ 0.05) effect on general acceptability of fortified soy milk. Maximum moisture content was obtained from fortificant concentration 2, 100, 32 mg/100 ml while that of total solids came from 3, 250, 24 mg/100 ml. Maximum acceptability came from fortificant combination 2, 200 and 32 mg/100 ml for ferric ammonium citrate, calcium carbonate and vitamin C respectively. Soy milk fortification should be carried out with caution. Ferric ammonium citrate should not be more than 2 mg/100 ml to avoid affecting the acceptability, while calcium carbonate should not be above 200 mg/100ml to avoid affecting the consistency, unless using stabilizer to prevent sedimentation.

Keywords: Micronutrient fortification, soy milk, sprouted soybeans, general acceptability, response surface methodology