Effects of Varying Weight Ratios of Large and Small Wheat Starch Granules on Experimental Straight-Dough Bread'

Cereal Chem. 82(2):166-172 One commercial bread wheat flour with medium strength (11.3% protein content. 14% mb) was fractionated into starch, gluten, and water solubles by hand-washing. The starch fraction was separated further into large and small granules by repeated sedimentation. Large (10-40 pm diameter) and small (1-15 pm diameter) starch fractions were examined. Flour fractions were reconstituted to original levels in the flour using composites of varying weight percentages of starch granules: 0% small granules (100% large granules), 30, 60, and 100% (0% large granules). A modified straight-dough method was used in an experimental baking test. Crumb grain and texture were significantly affected. The bread made The role of starch as a wheat flour component in breadmaking is still debated by cereal and starch scientists. On one hand, it has been recognized that starch deserves more importance as it relates to baking potential than simply acting as a "filler," as has been previously thought. The importance of starch in dough and bread structure had been demonstrated using starch and suitable surfactants by Jongh (1961), who suggested that gluten acts as a binder of starch granules. The literature concerning the role of starch in breadmaking was extensively reviewed and summarized by the following functions: 1) dilutes the gluten to a desirable consistency; 2) provides sugar for fermentation through amylase action; 3) provides a surface for gluten to form the wall of gas cells; 4) becomes flexible by gelatinization during baking, thus contributing to the gas-cell film; and 5) absorbs much water after gelatinization, which causes the cell-wall film to set and be rigid (Sandstedt 1961). Furthermore, the uniqueness of wheat starch compared with other cereal or noncereal starches was demonstrated for yielding a satisfactory loaf of bread (Hoseney et al 1971). Among the two types of wheat starch granules, the large A-type granules with a diameter of 10-35 pm are formed first in developing endosperm, whereas the small 13-type granules with a diameter of 1-10 pm are formed late in kernel development (Sandstedt 1961; Karlsson et al 1983; Dengate and Meredith 1984). The physical, chemical, and functional properties are different (Dronzek et al 1972; KuIp 1973; Nikuni 1978; Meredith 1981; Lineback 1984; Soulaka and Morrison 1985a; Morrison and Gadan 1987; Eliasson 1989; Peng et al 1999; Chiotelli and Le Meste 2002; Park et al 2004). Cooperative investigations, United States Department of Agriculture—Agricultural Research Service (USDA-ARS) and the Department of Grain Science and Industry, Kansas State University. Contribution No. 04-047-J from the Kansas Agricultural Experiment Station, Manhattan, KS 66506. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. 2 Research chemist, USDA-ARS. Grain Marketing and Production Research Center, Manhattan, KS 66502. Supervisory research chemist, USDA-ARS, Grain Marketing and Production Research Center, Manhattan, KS 66502. 4 Professors, Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506. Corresponding author. Phone: 785-776-2703. Fax: 785-537-5534. E-mail: [email protected] DOl: 10.1094/CC-82-0166 This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Association of Cereal Chemists, Inc., 2005. 166 CEREAL CHEMISTRY from the reconstituted flour with 30% small granules and 70% large granules starch had the highest crumb grain score (4.0, subjective method), the highest peak fineness value (1029), and the second-highest elongation ratio (1.55). Inferior crumb grain scores and low fineness and elongation ratios were observed in breads made from flours with starch fractions with 100% small granules or 100% large granules. As the proportion of small granules 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. Regarding the effect of starch granule size on baking potential, there are seemingly contradictory views on the effects of small 13type granules in breadmaking: 1) 13-type granules are beneficial (Hayman et al 1998b; Sahlstrom et al 1998; Van Vliet et al 1992); 2) 13-type granules are detrimental (Ponte et al 1963; D'Appolonia and Gilles 1971; Kulp 1973); 3) 13-type granules have little effect (Hoseney et al 1971); and 4) 13-type granules should be in optimum proportion with A-type granules for producing the best quality bread (Soulaka and Morrison 1985b; Lelievre et a! 1987; Park et al 2004). Van Vliet et al (1992) suggested that when the starch granules were much larger than the thickness of the gas-cell wall in dough, their presence resulted in much higher stress locally than average and, in turn, this stress could induce instability of gas cells, implying that the large starch granules are the cause of instability of the gluten film, more so than small starch granules. Coalescence would occur as a result, and poor crumb grain would be generated (Hayman et al 1998b; Van Vliet et al 1992). Sahistrom et al (1998) reported that 13-type granule content varied from 10 to 39% by volume in eight bread wheat flours, and larger loaves of bread were produced with flours containing more 13-type granules (2-2.3 pm). On the other hand, small wheat starch granules also have been reported to cause detrimental effects. Ponte et al (1963) observed that wheat starch granule size distribution and the extent of starch damage were inversely correlated with the breadmaking functionality of wheat starches. D'Appolonia and Gilles (1971) reported that granule size of wheat starches did not have a significant effect on loaf volume when the bread was made from a gluten-starch blend, but small starch granules showed a substantial decrease in loaf volume when the blend contained the water solubles. Small starch granules showed a lower baking potential than the unfractionated (mixture of large and small) granules, regardless of the source or method of preparation of the starch (KuIp 1973). However, small-granule wheat starch exhibited very little effect on loaf volume or water absorption but shortened the mix time compared with the control flour when it was reconstituted with gluten and water solubles (Hoseney et al 1971). An optimum proportion of 13-type granules (25-35% by weight of total starch) in a blend produced the largest loaf of bread when Soulaka and Morrison (1985b) used protease-prepared starch from cracked wheat and beyond the optimum point the bread volume decreased. However, there was a different optimum starch size for a given protein level when a starch-gluten blend containing sugar and yeast was used for breadmaking (Lelievre et al 1987). When a gluten-starch blend had a low gluten content, small starch granules were required to obtain optimum crumb grain and loaf volume. 0 5 10 15 20 25 30 35 40 45 50 55 12