Fatty acid composition of non-starch and starch neutral lipid extracts of Portuguese sourdough bread

Abstract

Fatty acids in each neutral lipid (NL) class from non-starch (NSL) and starch lipids (SL) were quantified in maize and rye flours, and sourdough-to ascertain the effect of mixing, and between sourdough and broa (a traditional Portuguese sourdough bread)-to assess the effect of fermentation. Maize and rye flour lipid extracts showed distinct fatty acid profiles. Maize flour exhibited a higher amount of most fatty acid species and of total NL-where triacylglycerols (TAG) and free fatty acids (FA) represented the dominant NL. The fatty acid profiles varied throughout breadmaking (i.e. from the mixture of flours with water, through fermentation until baking): in NSL, the highest concentrations were found in the flour mixture (i.e. 59 % of maize and 41 % of rye flour) or sourdough, whereas in SL they were found in broa; additionally, SL levels increased, and NSL levels decreased during dough preparation and baking. Palmitic (C16:0), oleic (C18:1) and linoleic (C18:2) acids were the major fatty acids in all food items. Cumulative percentages of C16:0, C18:1 and C18:2 in NSL and SL were over 81 and 75 %, respectively, in the flour mixture, 86 and 66 % in sourdough, and 83 and 82 % in broa. In particular, C18:2 accounted for 52 % of the total fatty acids. The content of sterol esters remained essentially constant throughout fermentation and baking; those of TAG decreased from flours to fermentation, while diacylglycerol and monoacylglycerol increased; the NL fractions were essentially unaffected by baking, yet their FA contents increased.