Date of Award

2011

Publisher

North Dakota State University

Document Type

Thesis

Degree Awarded

Master of Science (MS)

Program

Cereal Science

Department

Plant Sciences

College

Agriculture, Food Systems and Natural Resources

Faculty Advisor

Simsek, Senay

Description

Pre-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.

Rights

NDSU policy 190.6.2

Rights Link

https://www.ndsu.edu/fileadmin/policy/190.pdf

Handle Identifier

https://hdl.handle.net/10365/32815

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