Effect of malting on endosperm texture of Type 1 non-tannin sorghum grains and functional properties of the malted flour

Abstract

The effect of malting on endosperm texture and functional properties of the malted flour of two Type I sorghums (red and white phenotypes) was studied. Malting modified the endosperm of the two sorghums with a partial change from corneous to floury type, possibly due to the increased activity of α-amylase. The sprouted red sorghum grains appeared to have a higher proportion of floury endosperm than white sorghum grains. This could be attributed to the increased synthesis and activity of hydrolytic enzymes, such as α-amylase, which break down starch to provide energy for the germinating embryo, ultimately boosting the germinative energy of red sorghum. The α-amylase activity triggered during malting increased the sugar content and decreased the viscosity of starch during the pasting of the malted flour, suggesting starch depolymerisation. The degradation of starch decreased their ability to absorb water (water absorption index) and increased water-soluble compounds (water solubility index) in the medium. The action of protease enzymes in digesting some of the protein bodies and matrix surrounding the starch could also increase the accessibility of the starch to amylase enzymes. Malting is a promising green, traditional food processing technique to enhance the end-use quality of sorghum during processing.