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Neutral Lipids in Free, Bound, and Starch Lipid Extracts of Flours, Sourdough, and Portuguese Sourdough Bread Determined by NP-HPLC-ELSD

¹CBQF/Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal. ²Department of Applied Chemistry and Microbiology, P. O. Box 27 (Latokartanonkaari 11), FIN-00014 University of Helsinki, Finland. ³Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Tapada da Ajuda, P-1349-017 Lisboa, Portugal. ⁴Instituto Superior da Maia, Avenida Carlos Oliveira Campos, P-4475-690 Avioso S. Pedro, Portugal. ⁵CEBAL—Centro de Biotecnologia Agrícola e Agro-alimentar do Baixo Alentejo e Litoral, Rua Cidade de S. Paulo, Apartado 6158, P-7801-908 Beja, Portugal. ⁶Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da República, P-2780-157 Oeiras, Portugal. ⁷Corresponding author. Instituto Superior da Maia, Avenida Carlos Oliveira Campos, P-4475-690 Avioso S. Pedro, Portugal. Phone: (+351) 968 017 411. Fax: (+351) 229 825 331. E-mail: fmalcata@ismai.pt

A detailed analysis was developed, focused on the neutral lipids (NL) in free (FL), bound (BL), and starch lipid (SL) extracts of maize and rye flours, sourdough, and broa (a traditional bread manufactured in Portugal). Selective sequential extraction of said lipids with hexane at 20°C, water-saturated n-butanol at 20°C, and n-propanol-water (3:1, v/v) at 100°C was performed to clean the lipid extracts from extraneous impurities, and isolation thereof from glyco- and phospholipids was by solid phase extraction of NL; these classes were then quantitatively assayed by HPLC, using evaporative light scattering detection, with calibration curves prepared with standard mixtures of NL. The BL and SL contents in the original flours increased and that of FL decreased throughout the fermentation and baking processes. The dominant NL class was not the same in all lipid extracts; the highest concentrations of triacylglycerols and the lowest concentrations of free fatty acids were detected in FL—with the former accounting for 82, 76, and 71% of the total FL in flours, sourdough, and bread, respectively. Triacylglycerols and free fatty acids also accounted for the highest concentrations found in BL: these, together with diacylglycerols, contributed up to 84% of the total neutral BL. High levels of free fatty acids and low levels of the remaining NL classes were typically found in SL: free fatty acids, triacylglycerols, sterol esters, and diacylglycerols accounted for ≈90% of the total SL.