Size distribution and properties of wheat starch granules in relation to crumb grain score of pup-loaf bread

Twelve hard winter wheat flours with protein contents of 11.8-13.6% (14% mb) were selected to investigate starch properties associated with the crumb grain score of experimentally baked pup-loaf bread. The 12 flours were classified in four groups depending on the crumb grain scores, which ranged from 1 (questionable-unsatisfactory) to 4 (satisfactory). Flours in groups 1, 2, 3, and 4 produced breads with pup-loaf volumes of 910-1,035, 1,000-1,005, 950-1,025, and 955-1,010 cm(3), respectively. Starches were isolated by a dough handwashing method and purified by washing to give 75-79% combined yield (dry flour basis) of prime (62-71%) and tailing (7-16%) starches. The prime starch was fractionated further into large A-granules and small B-granules by repeated sedimentation in aqueous slurry. All starches were assayed for weight percentage of B-granules, swelling power (92.5degreesC), amylose content, and granular size distribution by quantitative digital image analysis. A positive linear correlation was found between the crumb grain scores and the A-granule sizes (r = 0.65, P < 0.05), and a polynomial relationship (R-2 = 0.45, P < 0.05) occurred between the score and the weight percentage of B-granule starch. The best crumb grain score was obtained when a flour had a weight percentage of B-granules of 19.8-22.5%, shown by varietal effects.