Effects of free lipid enrichment on the quality factors of wheat flour.

摘要

The free lipids (FL) of two commercial flours (medium-strength flour, MSF; soft white flour, SWF) were extracted by petroleum ether (PE), respectively, followed by reconstitution of defatted flours with various levels of FL. The quality factors of reconstituted flours such as gluten, farinograph and pasting properties were investigated. The results showed that with the increase of FL amount in MSF, wet gluten and gluten index did not vary significantly. As for SWF, the extraordinarily high gluten content (43.9%) was obtained when 2% FL was added to defatted flour, indicating that the obvious aggregation of gluten protein was caused by lipid addition. The sodium dodecyl sulfate sedimentation volume (SDS-SV) of MSF was increased but that of SWF was decreased due to FL enrichment. Farinograph absorption and degree of softening (DS) of both flours decreased but stability time (ST) markedly increased with increased FL content. SEM photos captured the reinforcing properties of FL as obvious gluten films could be found and many starch granules were covered with gluten in the oil-containing dough. As flours were enriched by FL, the pasting parameters including holding strength, final viscosity, and peak time of both flours were decreased, peak viscosity of SWF also decreased, but breakdown and setback of both flours were significantly increased. Polar lipid (PL) contents exerted remarkable influences on gluten and farinograph characteristics of MSF. With the increase of PL relative proportion of FL, wet gluten and ST of MSF reduced but DS increased significantly. These results suggested that nonpolar lipids (NL) in flour helped improve the dough tolerance to mix.