RELATIONSHIP BETWEEN ENDOSPERM TEXTURE AND THE OCCURRENCE OF FRIABILIN AND BOUND POLAR LIPIDS ON WHEAT-STARCH

Endosperm texture affects the milling and end-use properties of wheat grain. A better understanding of the physical-chemical mechanism and t he genetic control of endosperm texture in wheat would aid in breeding , marketing, and utilization of grain. Here, we report on the relation ship between endosperm texture and the occurrence of friabilin, a fami ly of 15-kDa proteins, and bound glyco- and phospho-lipids on water-wa shed wheat starch. These two classes of bound polar lipids follow the same pattern of occurrence as friabilin: approximately equal levels in soft and hard wheat flour, much reduced levels in water-washed soft w heat starch compared to flour, and much reduced levels in hard wheat s tarch compared to soft. The type and quantity of these bound polar lip ids is highly conserved among both soft and hard wheat starches. Furth er, these lipids are implicated in the interaction of friabilin with s oft wheat starch. Propan-2-ol and water (90:10), which is effective in removing bound polar lipids from starch, renders most friabilin compo nents extractable with an aqueous salt solution. These results suggest that most friabilin components interact with starch through lipid-med iated hydrophobic interactions and ionic interactions. In addition, th e results provide both an additional biochemical marker for grain soft ness and new insight into the possible physical-chemical mechanism and the genetic control of endosperm texture in wheat.