Epsilon Archive for Student Projects

Abstract

The quality of wheat bread depends on the molecular and structural composition of the utilized wheat flour, which is significantly impacted by the surrounding conditions during the cultivation of wheat grains. Thus, given the global warming, the quality of flours is altered. This thesis aimed to gather knowledge whether the quality of starch differ between two flours of low versus high quality, and whether any such differences impact the final bread quality. The examined flours were initially fractionated by kneading a wheat flour dough in excess water, with the obtained liquid starch phase being spray dried and the wet gluten phase freeze dried. The fractionation process was however not optimal, as the gluten phases still contained a large proportion starch. Analysis of the starch from quality wheat flour showed a slightly higher proportion of A-type granules, a significantly higher gelatinization temperature, and a significantly lower viscosity upon gelatinization.
Subsequently, to assess the impact of starch on final bread quality, six flours were analysed: two native flours of higher and lower quality, two reconstituted flours aimed to be identical with the native flours, one reconstituted flour made of gluten derived from high-quality flour and starch from low-quality flour, and the final flour reconstituted of gluten from low-quality flour and starch from high-quality flour. Breads made with the latter flour exhibited a significantly larger volume, darker crust, greater average crumb pore area, softer crumb texture, and less strong crust compared to the breads baked with the high-quality gluten and low-quality starch flour. These results could however not be predicted by viscoelastic measurements of doughs made of identical flours.
Regardless, the results indicates that the quality of starch indeed has a major impact on bread quality, and that flours of lower quality can be boosted by adding starch of higher quality. However, analysis of the reconstituted flours aimed to be identical with the native samples indicates that the starch separated from low-quality flour might be negatively affected by the fractionation process. Therefore, the results of this study may stem from quality differences obtained during the fractioning and reconstitution procedure. Still, the knowledge gathered is necessary for selection of wheat cultivars that can yield flours of high quality, regardless of global warming. Moreover, this offers a suggestion on how to improve the quality of already existing flours.