Short-Chain-Length Distribution in Debranched Rice Starches Differing in Gelatinization Temperature or Cooked Rice Hardness



Tropical nonwaxy and waxy rice starches differing in gelatinization temperature and previously characterized by high-performance gel permeation chromatography of debranched amylopectin were subjected to capillary electrophoresis of debranched starch to measure their amylopectin chain ratio (ACR, ratio A chains/A + B1 chains). The ACR data confirmed that low gelatinization temperature (GT) starch contained S-type (ACR ≥ 0.23) amylopectin and intermediate-high GT starch had L-type (ACR <0.20) amylopectin. ACR not only influenced GT, gelatinization enthalpy and ease of attack of starch granules by HCl and amylase, but affected also the extent of amylopectin staling of starch gels. Two japonica and two indica×japonica South Korean rices with low-amylose low-GT starch also contained S-type amylopectin.