Wheat (Triticum aestivum L.) lipid species distribution in the different stages of straight dough bread making.

Although wheat endogenous lipids strongly impact bread quality, knowledge on their detailed distribution throughout the different stages of straight dough bread making is lacking. We here compared the lipid populations in hexane [containing free lipids (FLs)] and water-saturated butanol extracts [containing bound lipids (BLs)] of wheat flour, freshly mixed and fermented doughs, and bread crumb using high-performance liquid-chromatography [for nonpolar lipids, i.e. mainly free fatty acids (FFA) and triacylglycerols] and electrospray ionization tandem mass spectrometry (for polar lipids). Freshly mixed doughs had lower FL and higher BL levels than flour, a phenomenon referred to as lipid-binding. Furthermore, probably due to the disintegration of flour particles, the overall extractability of nonpolar lipids was higher in freshly mixed dough than in flour. Dough fermentation decreased the extractability of glycolipids, but increased that of nonpolar lipids and phospholipids. We hypothesize that these phenomena result from stretching of the gluten network due to gas cell expansion, which leads to the replacement of some lipids associated with gluten proteins by others. Baking increased the extractability of bound lysophospatidylcholine (LPC) levels, but decreased that of free FFA. This is probably due to in situ dissociation of amylose-LPC inclusion complexes and formation of amylose-FFA inclusion complexes during bread baking and cooling, respectively. The approach and ESI-MS/MS methodology we developed provided valuable insights regarding the distribution of lipids at the different stages of bread making. Hence, it opens perspectives for future efforts to relate differences in lipid composition between wheat cultivars to their bread making quality.