|GREENBLATT G A|
|BETTGE A D|
|MORRIS C F|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/1994
Publication Date: N/A
Interpretive Summary: Wheat kernel texture, along with protein content, primarily determines the performance of the wheat grain in commercial mills, as well as the wheat's suitability for use in a particular food product. Texture, therefore, is a primary influence on a wheat's commercial worth. Wheat texture, or hardness, is genetically determined. The mechanism through which genetic grain hardness is expressed is poorly understood. A biochemical marker, the starch associated protein friabilin, has proved to be a reliable indicator of kernel softness; i.e. friabilin is present on soft wheat starch, but barely detectable on hard wheat starch. Although a good indicator of kernel texture, friabilin does not appear to actually cause softness. Two classes of starch bound polar lipids, glyco and phospho lipids, were consistently found to follow the same pattern of occurrence as friabilin. These lipids were found to be involved with the binding of friabilin to starch; friabilin may interact with starch only through the mediation of these lipids. The results show that starch bound polar lipids are an additional marker for kernel softness and will provide new insight into the physical chemical mechanism and genetic control of kernel texture in wheat. Once this mechanism is known, the information can be used to improve the ability of wheat breeding programs to produce wheat with enhanced commercial value.
Technical Abstract: Endosperm texture affects the milling and end use properties of wheat grain. Better understanding of the physical chemical mechanism and the genetic control of endosperm texture in wheat would aid breeding, marketing and utilization of grain. Here, we report on the relationship between endosperm texture, and the occurrence of friabilin, a family of 15 kDa proteins, and bound glyco and phospho lipids on water washed 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 wheat starch compared to flour, and much reduced levels in hard wheat starch compared to soft. The type and quantity of these bound polar lipids is highly conserved among both soft and hard wheat starches. Further, these lipids are implicated in the interaction of friabilin with soft wheat starch. Propan-2-ol:water (90:10), which is effective in removing bound polar lipids from starch, renders most friabilin components extractable with an aqueous salt solution. These results suggest that most friabilin components interact with starch through lipid mediated hydrophobic interactions and ionic interactions. In addition, the results provide both an additional biochemical marker for grain softness and new insight into the possible physical chemical mechanism and the genetic control of endosperm texture in wheat.