Effects of lipid surfactants on the structure and mechanics of concentrated starch gels and starch bread

The effects of lipid surfactants (emulsifiers) on changes in the mechanical properties of concentrated starch systems during heating, cooling and storage were studied. In the presence of glycerol monostearate (GMS) or sodium stearoyl-2-lactylate (SSL), the dynamic moduli of potato and wheat starch systems during heating and cooling were somewhat higher, and the increase in stiffness of the gels during storage was slightly retarded. Furthermore, the fracture stresses and strains of these starch gels were lower when GMS or SSL were added. These changes in mechanical properties were ascribed to formation of complexes between amylose and the Lipid surfactants. No effects of GMS and SSL on the mechanical properties of waxy maize starch systems were observed. The effects of GMS and SSL on the mechanical properties of wheat starch bread were also studied. Neither the increase in the Young's modulus during storage nor the recrystallisation of amylopectin were affected significantly by these substances. However, the large deformation properties of the breads were affected. The effects of lipid surfactants on the mechanical properties of starch gels and starch bread are compared. (C) 1996 Academic Press Limited