STARCH PROPERTIES AND STABILITY OF CLUB AND SOFT WHITE WINTER WHEATS FROM THE PACIFIC-NORTHWEST OF THE UNITED-STATES

Based on examination of 192 club and soft white winter (SWW) wheat sam ples, club and SWW wheat flours showed comparable levels of starch dam age and flour peak viscosity, while differing significantly in starch content. Varietal differences and growing conditions had strong influe nce on the characteristics of both classes of wheat flour. Club wheat flour exhibited better stability in starch content and starch damage t han did SWW wheat flour. A significant correlation between starch dama ge and cookie diameter in both club and SWW wheat was observed (r = -0 .480, P < 0.0001 for club wheat and r = -0.430, P < 0.0001 for SWW whe at). Sponge cake volume was positively correlated with starch content in both classes of wheat (r = 0.362, P < 0.01 for club wheat and r = 0 .181. P < 0.05 for SWW wheat). When wheat samples were grown in one lo cation over three years, club and SWW wheat flours had comparable star ch content. However, flour and prime starch peak viscosities were sign ificantly different in club than in SWW wheat. Club wheat flour had lo wer starch damage and amylose content, as measured by high-performance size-exclusion chromatography (HPSEC), than did SWW wheat flour. Crop year and varietal differences had significant effect on amylose conte nt, starch damage, and flour and starch peak viscosities, but not on s tarch content, in both classes of wheat flour. When wheat samples were grown in one year over seven locations, club wheat flour was higher i n starch content, lower in starch damage, and comparable in amylose to SWW wheat flour. Both flour and prime starch viscosities were signifi cantly higher in club wheat than in SWW wheat. Varietal differences an d growing location had strong influence on starch properties in both c lasses of wheat. Peak viscosity of the isolated starch did not correla te well with the corresponding flour, indicating that flour pasting pr operty does not reflect the pasting property of starch. The fine struc ture of isoamylase-debranched amylopectins from club and SWW wheats ha d a similar trimodal pattern, with maximum at approximate to DP 15 and two valleys at approximate to DP 20 and 45, respectively. Although wh eat flour samples differed widely in their prime starch peak viscosity , no significant difference between debranching patterns was obtained. These results indicate that the fine structure of amylopectin might n ot be responsible for the large differences in prime starch pasting pr operty.