Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2004
Publication Date: 3/1/2005
Citation: Park, S., Chung, O.K., Seib, P.A. 2005. Effects of varying weight ratios of large and small wheat starch granules on experimental straight dough bread. Cereal Chemistry. 82:166-172
Interpretive Summary: Wheat flour has generally two types of starch granules including large granules and small granules that are different in their physical and chemical properties. We demonstrated how the different size distribution of starch granules affect the breadmaking quality, especially on bread crumb appearance, by fractionating flour components and starch fractions and then reconstituting, adding back those fractions into a flour. We used a commercially available bread wheat flour and fractionated it into three fractions (starch, gluten, and water-solubles), and the starch fraction was further separated into large and small granules. The flour was reconstituted with the original levels of flour fractions, using starch composites of varying amounts of large and small granules, and then was baked. Crumb appearance and texture were significantly different, depending on how much small or how much large starch granules were in the reconstituted flours. When the reconstituted flour contained a starch mixture of 30% small and 70% large starch granules, it produced bread with the best crumb appearance. If flour contained starch fraction of all small grains or all large grains, it produced a loaf of bread with inferior crumb grain score, i.e. both fineness and elongation ratios were very low. However, as the amount of small starch granules increased in the reconstituted flour, it produced loaf of bread with softer texture during storage.
Technical Abstract: One commercial bread wheat flour with medium strength (11.3% protein content on 14% mb) was fractionated into three fractions (starch, gluten, and water-solubles) by hand-washing. The starch fraction was further separated into large and small granules (LG and SG) by repeated sedimentation. Sizes of large (10-40 um in diameter) and small (1-15 um in diameter) starch fractions were examined. Flour fractions were reconstituted to their original levels in the flour, using composites of varying weight percentages of starch granules: SG being 0% (100% LG), 30%, 60%, and 100% (0% LG). A modified straight-dough method was used in an experimental baking test. Crumb grain and texture were significantly affected: the bread made from the reconstituted flour with 30% SG and 70% LG starch had the highest crumb grain score (4.0, subjective method), the peak fineness value (1029) and the second highest elongation ratio (1.55). Inferior crumb grain scores, low fineness and elongation ratios were observed in breads made from flours with starch fractions at 100% SG or 100% LG. As the proportion of SG increased in the reconstituted flour, it yielded bread with softer texture that was better maintained than the bread made from the reconstituted reference flour during storage.