Solvent solubility parameter and flour moisture effects on lipid extractability

Lipids were extracted with a series of solvent systems whose solubility parameter (δ) values ranged from 7.27 to 12.92 (hexane and its aqueous azeotrope, benzene, acetone and its azeotrope and 2‐propanol and its azeotrope) from a flour with 1.2%, 7.2% or 13.8% moisture content (MC). The extracted total lipids (TL) were fractionated into nonpolar lipids (NL) and polar lipids (PL) by silicic acid column chromatography. NL and PL were further subfractionated by thin layer chromatography (TLC). PL were separated into glycolipids (GL) and phospholipids (PhL). TL, NL and PL extractabilities were affected by both flour MC and by the nature and composition of extractants: the overall solvent effects were substantially more pronounced than the flour MC effects. Free fatty acid and digalactosyldiglyceride (DGDG) extractabilities increased for all extractants, in general, as flour MC increased. Significant linear relations between the δ values of extractants and the average amounts of TL, PL, GL and PhL from flours with 3 MC were found. The high correlation (r=0.981) between δ and extractability of TL was primarily caused by PL; extractabilities of monoglycerides (among NL) and all classes of GL and PhL were significantly (at the 0.01 level) linearly related to the δ values at all 3 flour MC levels. The present study indicated no selective binding between flour proteins and a specific PL class. Among PL, DGDG showed a clear‐cut breaking point in irreversible restoration of breadmaking characteristics. Thus, the present study confirms the significant role of PL to breadmaking, resulting primarily from the contribution of DGDG.