The Role of Hydrogen Bonding in Amylose Gelation

Abstract

Abstract Studies of the rheological properties of amylose gels in mixtures of water and DMSO have shown that these properties are dependent upon the formation of intramolecular and intermolecular hydrogen bonds. In DMSO, it is proposed that amylose has a tight helical conformation which is maintained by intramolecular hydrogen bonding. When water is added it is proposed that intramolecular hydrogen bonds are replaced with intermolecular hydrogen bonds and thus the rheological properties are changed due to the more extended and flexible amylose molecules adopting an interrupted helical conformation. Because of these changes in conformation, increased water content results in strong elastic gels, commensurate with it being the dominant gel‐forming component in starch, due to its ability to form networks with water through intermolecular hydrogen bonding. The addition of various polyols to solutions of amylose in DMSO also resulted in strong elastic gels being formed. It is proposed that polyols such as 1,3‐propanediol are also able to form networks in a similar way to water. The use of intermolecular hydrogen bond breaking agents, such as urea, reduced gel strength significantly, but the intra‐molecular bond‐breaking agent, 1,1,3,3‐tetramethyl urea (TMU), was not so effective. The results of this work are further evidence of intermolecular hydrogen bonding networks between amylose and water as being of fundamental importance in the strength of starch gels.