Characterization of Physicochemical Properties of Annealed Corn Flour and Starch: A Verification of Meta-Analysis

Abstract

This study examines the effects of annealing process (temperature 50 °C, moisture content of 80%, for 20 h) on physicochemical characteristics (proximate composition, content of resistant starch (RS) and amylose, degree of starch digestibility, shape and size of starch granules, crystallinity, and starch gelatinization profile) of corn flour and corn starch. Two stages of experiment are as follows: 1) verifying the results of the meta-analysis of corn starch and flour modification by annealing method and 2) analyzing their physicochemical properties. As a result, annealing significantly improves RS content in both groups, reaching 14.18% in annealed corn flour (AF) (compared to 3.27% in native corn flour (NF)) and 21.87% in annealed corn starch (AS) (compared to 3.82% in native corn starch (NS)). The present work also confirms that the treatment unaltered birefringence properties of all samples. Moreover, pasting properties of corn starch and flour demonstrate remarkable changes. The peak viscosity of AS and NS is higher than AF and NF. In addition, gelatinization seems to occur at similar temperature, but needs extra time for starting gelatinization. XRD analysis reveals A-type crystalline for all samples, while FTIR analysis evidenced that annealing process alters the regions of amorphous and crystalline.