EFFECT OF SODIUM ALKALIS AND SALTS ON pH AND FLAVOR OF SOYMILK

Abstract

ABSTRACTSodium hydroxide, sodium carbonate and sodium bicarbonate were added to soymilk made by the “boiling‐water grind” process. NaOH caused a rapid increase in pH; Na2CO3 a moderate increase and NaHCO3 a slight increase in pH. After sterilization in bottles the pH of the soymilks containing alkali decreased, with the decrease least with the NaHCO3 treatment and greatest with the NaOH treatment. The pH of the untreated soymilk did not change during sterilization. An experienced taste panel showed greater acceptability for soymilk adjusted to pH 7.0‐7.5 with NaOH but noted a soapy flavor and gave lower scores for milks with pH greater than 7.5. Soymilks adjusted to pH 7.0‐7.5 with Na2,CO3 or NaHCO3 were disliked by the panel. We theorized that the improved acceptability with NaOH could be due to the increase in sodium ion concentration rather than the change in pH. Soymilks prepared with Na2CO3, NaHCO3, NaNO3, Na2SO4, Na acetate and Na citrate additions at the same levels as that amount of NaOH required to raise the pH to 7.2 were given approximately the same scores by the panel as the NaOH‐treated sample even when the pH was not in the range of 7.0‐7.5. This evidence supports the theory that the sodium ion concentration is the effective mechanism in improving the flavor of soymilk rather than the change in pH.