Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2009
Publication Date: 1/13/2010
Publication URL: http://hdl.handle.net/10113/38282
Citation: Finnie, S.M., Jeannotte, R., Morris, C.F., Giroux, M.J., Faubion, J.M. 2010. Variation in polar lipids located on the surface of wheat starch. Journal of Cereal Science. 51:73-80. Interpretive Summary: Wheat starch constitutes 70–75% of the flour and is composed of three distinctive types of granules: A-type, B-type and C-type. The objective of this study was to determine the variation in polar lipids present on the surface of wheat starch granules. Variation in the starch granule surface polar lipids was evaluated either from genetic variation or by the starch isolation processes. Genetic variation studies were conducted using three pairs of near-isogenic wheat lines that varied in their puroindoline expression and kernel hardness. Induced variation studies were conducted using two very different starch isolation processes: a dough-ball method representing starch after experiencing dough development, and a batter method, representing starch that had not experienced dough development. The conclusion of this research is that when dough is mixed to the optimum level, lipids on the surface of wheat starch become incorporated into the gluten of the dough. In a batter, the lipids stay on the granule surface.
Technical Abstract: The starch granule surface contributes the greatest proportion of surface area in a dough, and it is unknown whether starch isolated before dough development would have the same surface lipid composition as starch isolated after dough development. The compositional structure of the surface of wheat starch granules plays a crucial role in wheat endosperm hardness. The abundance of starch granule surface polar lipids is related to the physical hardness of the endosperm, but the variation in specific lipid class and molecular species is unknown. The objective of this study was to quantitatively determine the variation in polar lipids present on the surface of wheat starch granules. The experimental wheat lines used are, within each set, near-isogenic to each other but vary in grain endosperm hardness. Starch was isolated using two different processes: a dough and a batter method. Direct infusion electrospray ionization tandem mass spectrometry was used to identify and quantitatively determine the polar lipid species in wheat flour and starch. Wide ranges in starch surface polar lipid concentrations were observed between the two starch isolation methods. Starch isolation method provided a greater source of variation than wheat kernel hardness. When dough is optimally mixed, lipids originally on the surface of wheat starch become incorporated into the gluten phase of the dough, whereas in a batter system, starch surface lipids stay associated with the starch granule surface. The predominant starch surface polar lipids were di-acyl lipids of digalactosyldigylcerol (DGDG), monogalactosyldigylcerol (MGDG) and phosphatidylcholine (PC) polar lipid classes, and the predominant internal starch polar lipids were lysophosphatidylcholine (LPC) lipids