Lactic acid esterification of maize starch in solid state: Assistant effect of pullulanase modification on digestibility and physicochemical properties

Abstract

The current work was the first report to prepare lactate-esterified debranched starch (LEDS) in solid state mode. Normal maize starch (NS) was initially modified by pullulanase enzyme in granule form and then esterified with lactic acid under dry heating for 3 h at 80 °C and presence of 0.2% w/w sodium hydroxide. Physicochemical properties of the treated starches by single and dual treatments were determined and compared with NS. The enzymatic modification could improve reaction efficiency of esterification process up to 75.2% through partial hydrolysis of starch chains. Compared with NS and individual modifications, the combined treatment significantly increased amylose extent, and the amount of resistant starch (RS) while decreased the freeze thaw stability, viscosity, gelatinization temperatures, paste clarity, swelling power, and relative crystallinity. The morphological examination showed dissociation and degradation of starch granules by single and dual treatments. FT-IR confirmed the introduction of ester groups onto the starch molecules through a band at 1715 cm−1. The impact of designed dual treatment on the environment was assessed by applying Eco-scale index, proving the greenness of the method (score: 75). The findings of this study will provide a theoretical background for development of high RS food products.