Mechanism underlying V-type structure formation in maize starch through glycerol–ethanol thermal substitution method

Abstract

V-type starches have been widely used in food science, agriculture, and biomedical science, but their mechanism of formation in nonaqueous solvents remains unclear. This study performed glycerol–ethanol thermal substitution to prepare V-type starch at atmospheric pressure. Scanning electron microscopy and confocal laser scanning microscopy revealed that breakage of starch particles began in the hilum region and rapidly spread to the periphery with the temperature increased from 100 °C to 130 °C. The Maltese crosses of the starch disappeared and starch particles had the form of doughnut-shaped rings when the glycerol temperature was 140 °C. Glycerol temperature was not found to significantly affect the chain length of amylopectin, meaning that glycerol molecules may stabilize the conformation of amylose through hydrogen bonding, promoting the amylose to form a V-type spiral structure. Additionally, A-type crystallinity and double helix structure proportion of the samples significantly decreased from 30.81 % and 42.21 % to 5.70 % and 16.47 % as the temperature of glycerol was increased to 140 °C, whereas the V-type crystallinity and single helix structure proportion of the samples remarkably increased from 13.26 % and 1.05 % to 37.97 % and 25.09 %, respectively. This study provided a facile and versatile approach to effectively regulate the formation of V-type starch.