Influence of growth conditions on barley starch properties.

Air equilibrated barley starch comprises amylopectin, amylose, lipid and water. The structure of amylose and amylopectin, and the proportion of amylose in granules is under genetic control and is therefore subject to genotypic variation. The amount of lipid (which is essentially all lysophospholipid) is similarly under genetic control. Environment and especially environmental temperature do, however, have a regulatory effect on the size of starch granules, the amylose to amylopectin ratio and the amount of lipid (which is essentially all complexed with amylose) within barley starch. High growth temperatures probably facilitate amylopectin crystallisation and increase gelatinisation temperatures, (and to some extent the enthalpy of gelatinisation), but delay the onset and depress the extent of swelling of granules when heated in water.