Composition of neutral lipid classes and content of fatty acids throughout sourdough breadmaking

Broa is an example of bread that is a good candidate for inclusion in functional diets, so it deserves further in-depth study of its chemical composition-namely with regard to evolution of the lipid profile throughout breadmaking, in order to assess whether mixing, fermentation, or baking affect its nutritional value (in terms of unsaturated fatty acids, UFA) based on the assumption that neutral lipids (NL) can be protein- or carbohydrate-bound. Hence, constituent fatty acids in NL of maize (Zea mays) and rye flour (Secale cereale), and in sourdough and final broa manufactured from a mixture therefrom were quantitated. Methodologies of esterification of fatty acids, as well as of transesterification of acyl lipids and sterol esters (SE) were improved. The n-hydrocarbons containing between 4 and 24 carbon atoms were then resolved and identified by gas-liquid chromatography. Regarding total neutral lipids (TNL) in all samples, 79-89% were TAGs, and 87-93% were TAGs and DAGs in the case of free lipids (FL). Furthermore, 73-85% of TNL in bound lipids (BL) and 65-80% of TNL in starch lipids (SL) were TAG and free fatty acids (FFA). Conversely, only 4-5%, 6-16%, and 7-10% of TNL in FL, BL, and SL, respectively, were SE and MAGs. TAGs and DAGs underwent partial hydrolysis during fermentation and baking; palmitic, oleic, and linoleic acids were dominant as products released. The nutritional value of broa lipids was apparent owing to their proportions of SE (4%) and DAG (9%), coupled with 52% of linoleic acid in all samples-as well as to the high contents of polyunsaturated versus monounsaturated or saturated fatty acids, and to the general dominance of UFA.