Impacts of Molecular Structure on Complexation between Rice Starches and Iodine or Concanavalin A

• Main Authors: Liao Men-Chun, 廖孟君
• Other Authors: Cheng-yi Lii
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/16658398382477263500

碩士 === 國立中興大學 === 食品科學系 === 91 === Abstract The impacts of starch molecular structure on complexation between rice starches and iodine or Concanavalin A were investigated. Three indica (KSS7, TCN1, TCS17), two japonica (TG9, TNu67), and one waxy (TCW70) rice starches were used as samples, to prepare their hot-water soluble fractions for iodine or Con A complexation and fine structure measurements. In the case of starch-iodine complexation, the absorbance at 620 nm (A620) of the complexes showed that higher-amylose content (AC) rice starches displayed certainly a higher A620. Increasing extracting temperature resulted in an increased AC in soluble materials. The sensitivity for standard curve of AC determination was lowest for potato amylose (AM)- amylopectin (AP) mixtures and highest for potato AM-TCW70 (AP) mixtures. For starch-Con A complexation properties, the proper conditions were starch:Con A ratio = 1:3 (w/w) and centrifugation for the complexes with 14,000 g. Both amylopectin and hot-water soluble fractions (rich in AM) were able to precipitation after complexing with Con A. A lower-AC starch yielded a greater precipitation whatever the incorporation of Con A or not. Between rice varieties, the amount of Con A-complexed precipitates from the soluble starch materials were TCW70>TNu67 > KSS7, TCN1, TCS17 and TG9; and the extracts of 80 and 90oC (S80 and S80-90) > that of 100oC (S90-100). As to the molecular properties of S80, S80-90 and S90-100, the S80 and S80-90 of TCN1 or TG9 varieties showed individually a bi-modal molecular distribution, and the S90-100 exhibited a single (TCN1) or tri-modal (TG9) distribution. The Con A- complexed molecules of S90-100 for TCN1 and TG9 were, respectively, with a DP > 204 and 602 and in a proportion of 52% and 31. Generally, the chain distributions of these hot-water-soluble fractions were single distribution and mainly with a CL = 10-11. The degree of branching of the soluble fractions was greatest for TCW70 variety, followed by TG9 and least for TCN1 and KSS7 ones. For the S80, S80-90 and S90-100 of KSS7 and TCN1, the AC changed with extraction temperature in a similar way by between iodine colorimetry and Con A- enzymatic methods. However, the AC for TG9 soluble fractions tended to increase and invariant with extraction temperature by these two AC-determining methods, respectively. These phenomena could be related to the chain distribution of TG9 solubles, of which the S90-100 possessed a longer CL (primarily DP = 6-9) and more spherical branching structure than the lower temperature extracts, despite these fractions were of similar degrees of branching.