Effect of enzymatic and heat-moisture treatments on the physical and structural properties of granular starches

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서울대학교 대학원
Thesis (master`s)--서울대학교 대학원 :농생명공학부,2004.
The glucosyl-transferase changes the amylose contents, amylose-amylopectin ratio, and the size
of branched-chain of amylopectin in starch, and these factors influence the physical and
structural properties of starch. Corn, sorghum, and wheat starches were treated with α- 1,4-α-
1,4-glucosyl transferase from Thermocus aquaticus YT1 (TAαGT) to change the physical and
structural properties of starch.. The amount of amylose was measured using colorimetric method
by amylose-iodine complex, and the change of wave-scanning pattern was measured in the range of
400 - 800 nm. Enzymatically treated starches showed lower levels of amylose content than raw
starches, and the patterns of wave-scanning were turned to more amylopectin-like patterns.
Thermal properties of enzymatically treated starches were measured by differential scanning
calorimetery (DSC). DSC profiles showed that enzymatically treated starches showed lower
gelatinization enthalpy, higher peak temperature, and broader melting temperature area than raw
starches. The size distribution of enzymatically treated starch was measured by high-performance
size exclusion chromatography (HPSEC). The results showed that the size of amylopectin was
shorter and more variable than raw starches, and the intermediate molecular weight (IMW) and low
molecular weight (LMW) fractions were increased. The rheological behavior was measured by using
an oscillatory rheometer. The results of frequency sweep measurement showed that the gel of
enzymatically treated starch had higher storage modulus (G’) and loss modulus (G’’) than raw
starches, and the structure of the enzymatically treated starch gels was collapsed during
temperature sweep measurements. The results of dynamic viscoelasticity during heating and
cooling cycle showed that the solid-like structure of enzymatically treated starch at room
temperature turned to liquid-like structure at 70oC and the liquid-like structure turned to
solid-like structure relatively reversibly at room temperature. Thus enzymatically treated
starches could be used in the starch-containing food system as the anti-staling materials and
the fluidity-enhancing materials. For the more precise study of structural properties, the fine
structure of amylopectin shoud be investigated.
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College of Agriculture and Life Sciences (농업생명과학대학)Dept. of Food and Animal Biotechnology (식품·동물생명공학부)Theses (Master's Degree_식품·동물생명공학부)
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