Physicochemical properties of corn starch selectively oxidized with 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion

Abstract

This study was conducted to examine the characteristics of oxidation reaction on the primary alcohol groups in corn starch, when 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion (TEMPO) was used, and to determine the optimum conditions for the preparation of oxidized corn starch (OCS). Applicability of the OCS in the food system was also investigated. The effects of TEMPO, sodium bromide (NaBr), and temperature on oxidation reaction time, yield, and selectivity for primary alcohol groups were examined by response surface methodology. As the temperature and the levels of TEMPO and NaBr increased, reaction time and selectivity decreased. Yield decreased with increased NaBr and selectivity decreased with the increased temperature and NaBr. Selectivity increased with higher TEMPO levels up to a certain point and then decreased. Optimum levels of TEMPO, NaBr, and temperature for the preparation of OCS were determined as 0.6 mM/100 mM of anhydroglucose unit (AGU), 45 mM/100 mM AGU, and 7°C, respectively. Water binding capacity, emulsion stability, and viscosity of starch increased significantly by oxidation. Corn starch containing OCS had decreased initial pasting temperature, setback, and gelafinization and retrogradation enthalpy (AH). Corn starch gel containing OCS showed delayed staling during storage.