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Item Physicochemical Properties of Pre-Harvest Sprouted Hard Spring Wheat(North Dakota State University, 2011) Lu, HaiyanPre-Harvest Sprouting (PHS) can cause severe economic loss in wheat grown across many areas of the world. Prolonged rainfall before harvest and high temperatures can contribute to the occurrence of PHS. Grain growers prefer wheat genotypes with low susceptibility to PHS. The objective of this study was to examine the physicochemical properties of Hard Red Spring Wheat (HRSW) and Hard White Spring Wheat (HWSW) affected by PHS. Physicochemical properties of the starch and protein in HRSW and HWSW were significantly affected by PHS. α-Amylase was determined using an Azurine-crosslinked amylose substrate (AZCL-Amylose; Megazyme Co., Ltd). Endo-protease activity was determined using an Azurine-crosslinked substrate (Protazyme AK tablet; Megazyme Co., Ltd). Mean value of α-amylase of PHS damaged wheat (2.00 CU/g) was 17 times greater than sound wheat (0.12 CU/g). Mean value of endo-protease of PHS damaged wheat (2.30 A_{590}/g/h) was 1.6 times higher than sound wheat (1.44 A_{590}/g/h). PHS increased both α-amylase and endo-protease activities, resulting in the hydrolysis of starch and protein molecules. However, the increased endo-protease activity was not as significant as the increase in the α-amylase activity in PHS wheat. In a scale of 1.0-9.0, the wheat genotypes had significantly different sprouting scores ranging from 2.5 to 7.8, which had positive correlations with α-amylase and endoprotease activities (P<0.001 ). Consequently, genotypes showed differences in degradation of starch and protein molecules. The endo-protease activity of PHS samples had greater correlation (r= 0.78) with protein degradation measured by High Performance Size Exclusion Chromatography (HPSEC) than with sprouting score (r = 0.57). The degree of protein degradation was better estimated by the endo-protease activity than sprouting score in PHS samples. The pasting properties of starch were measured by Rapid Visco Analyzer (RVA). Mean value of peak viscosity of PHS damaged wheat decreased up to 96% compared to that of sound wheat sample. HPSEC was used to detect the starch molecular weight distribution. PHS damaged wheat had lower molecular weight for high molecular weight amylopectin (HMW-AP) and higher molecular weight for low molecular weight amylopectin (LMW-AP) and amylose. This result indicated that PHS had changed the molecular weight distribution of starch. Sodium Dodecyl Sulfate (SDS) buffer extractable proteins (EXP) and un-extractable proteins (UNP) were analyzed by HPSEC. Some portion of UNP had changed to EXP. The result indicated that the molecular weight distribution of protein had been changed due to PHS.Item Effect of Amylase Content and Gluten on Gelatinization and Retrogradation of Starch Blends and Starch/Gluten Blends and on Bread Staling(North Dakota State University, 2010) Matkovic, Kornelija;Effect of amylase content and gluten on starch gelatinization and retrogradation properties, and consequently bread staling, still is not clear. In the case of starch and starch/gluten blends, information on the relationship between functional properties of starch blends and amylase and gluten contents is scarce. Effects of amylase content on baking and staling properties of bread were investigated by using 20, 30, and 40% blends of waxy spring (WS) or waxy durum (WD) wheat flour with non-waxy wheat flour. Crumbs with 30% and 40% waxy flour exhibited very open, porous structure. Retrogradation enthalpies and bread firmness were higher for waxy than for non-waxy crumbs and higher for WD than for WS crumbs at the end of storage (5 days), although waxy crumbs had a higher amount of soluble starch (especially WD crumbs) than non-waxy crumb. Results indicated that retrogradation and staling are complex processes that depend not only on amylase content, but also possibly on interactions of starch with other crumb components or interactions between two starches in a blend. To elucidate the effect of amylase content and gluten on properties of starch, blends of WD starch (0, 12.5, 25, 50, 75, and 100% w/w) and non-waxy starch, as well as starch blends combined with 30% gluten were studied. Gelatinization and retrogradation properties, as well as properties of soluble starch isolated from gels after 5, 10, 15, 20 days of storage and fractionated by gel permeation chromatography (GPC}, were studied. Gelatinization enthalpy (11H) was higher for blends with low than for blends with high amylase content. However, l).H was not significantly different between each consecutive blend although their amylase contents were different. Retrogradation enthalpy of starch blends (l).HaR) increased during 20 days of storage. On each storage day, M-laR was lower for low amylose blends than for high amylose blends, showing that low amylose content in starch blends slowed the process of retrogradation. Similar to t:.H, M-laR was not significantly different between each consecutive blend. Apparently, gelatinization and retrogradation properties of starch blends with different amylose contents were more complex than in single starches and could not be interpreted as a simple sum of contributions of individual components. Gluten did not affect gelatinization enthalpy of starch blends due to excess amount of water in the system. However, it significantly lowered the M-laR of low amylose blends (50, 75, 100% WO) compared to that of high amylose blends, especially on day 15 and day 20, which was interpreted as the result of gluten interacting with branched starch molecules. Analysis of GPC fractions of soluble starch showed that retrogradation patterns of O wx, 12.5 wx, and 25 wx blends were different, although their M-laR were similar. Low proportion of branched fraction in O wx soluble starch after day 5 and low ratio of blue value/total peak carbohydrate on days 15 and 20 indicated retrogradation due to reassociation of branched molecules with long chains. In 12.5 wx and 25 wx soluble starch, low values for the wavelength of maximum iodine absorption (Amax) of linear fraction indicated that some amylopectin fragments eluted with the linear fraction. Recrystallization of these molecules could have been facilitated by the presence of amylase in the fraction. Gluten affected retrogradation pattern of starch by promoting reassociation of branched molecules (reduction in A.max) at the beginning of storage. All starch/gluten blends had similar retrogradation patterns. Overall, amylose content affected gelatinization and retrogradation properties of starch significantly; however, in starch blends these properties were not simple averages of properties of two starches. In addition to the amylose content, properties of blends also could be governed by specific interactions between two starches or between starch and gluten.