Lipid Interactions in Unworked Wheat Flour Doughs

Abstract

A method of adjusting flour moisture level without the introduction of mechanical work was developed to study resulting lipid redistribution, changing physical properties and water distribution. Three flours, two similar and one of different composition, were found to show closely similar qualitative and quantitative patterns of lipid redistribution. Both extractable and unextractable additional binding of both neutral and polar lipid was produced by work-free hydration, the pattern changing as water distribution changed and unworked dough structures developed. When flour was fully hydrated, all polar lipid was extractably bound and a third of all neutral-lipid bound, both extractably and unextractably in equal proportions. A method was developed to successfully reconstitute solvent extracted flours with the extracted flour lipid and to add to such extracted flours, neutral fractions of extracted flour lipid, both a liquid and solid triglyceride fat and also a flour lipid fraction containing a low proportion of neutral lipid. These manipulations were shown to produce redistribution of bound lipid. Work free wetting of these reconstituted flours produced increased binding of liquid, neutral lipid. Critical moisture levels in the development of unworked dough structure were revealed by changes in lipid migration patterns during the course of simple hydration. Even more neutral lipid binding was produced in mechanically developed doughs although reduced slightly by the presence of added salt. A differential thermal analyser was used as a calorimeter to show that worked doughs, with different total moisture contents, had the same distribution of freezable and unfreezable water which was unaffected by the presence of salt. No added salt was found in solution in freezable water of these doughs. The results of this study of simple hydration were discussed in terms of a hypothetical lipid binding site and related to other work with mechanically developed doughs.