Nutritional and functional properties of decorticated and microwave heat moisture treated white sorghum meal with added non-tannin and tannin phenolic extract

Abstract

Emerging technologies, particularly microwave energy, have proven to be more efficient for heat moisture treatment to enhance starch functionality. In a sorghum food system, interactions between starch-phenolics and protein-phenolics significantly influence the nutritional properties of the food. Microwave heat moisture treatment decreased the starch hydrolysis index of sorghum meals from 69.89 % to 54.33 % in samples without phenolic extracts. The hydrolysis index was further reduced from 59.27 to 35.99 % and 54.74 to 36.18 % in samples containing non-tannin and tannin phenolic extracts. The addition of phenolics led to increased resistant starch content, characterized by higher levels of slowly digestible starch and a lower glycaemic index. The interactions between phenolic compounds, protein, starch, and the α-amylase enzyme contribute to the increased resistant starch content. Specifically, phenolics and proteins form barriers around starch granules that hinder digestion. Furthermore, interactions between phenolics and amylose further decrease digestibility while inhibiting α-amylase activity.

HIGHLIGHTS • Microwave heat moisture treatment of sorghum meal slows down starch hydrolysis • Adding phenolic extracts further reduces starch digestibility • Phenolic addition and heat moisture treatment increases resistant starch