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Submitted to: Carbohydrate International Symposium
Publication Type: Abstract Only Publication Acceptance Date: 8/14/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Starch consists of two types of alpha-glucans: amylose, which is mostly linear and has only a low level of branching, and amylopectin, which is highly branched. Recently, a nuclear magnetic resonance (NMR) method was developed to accurately measure branching in starch, and those NMR branching ratios were used to determine amylose/amylopectin fractions in a variety of starches. In the course of those determinations, evidence was found for three different types of amylopectin, based on its branching, with highly branched amylopectin coming from waxy cornstarch, rice and tapioca starches, medium branched amylopectin coming from dent cornstarch, potato and wheat cornstarches, and the least branched amylopectin coming from high amylose cornstarches. Many starch applications, both food and industrial, are improved by using a more linear starch. High amylose cornstarches have found increasing use because of their enhanced linearity versus normal starches. Higher prices for such specialty starches and the complexity and cost of debranching normal cornstarch using specific debranching enyzmes has limited the use of highly linear starches. However, it appears that certain extrusion conditions lead to debranching of starch, even when starting from highly branched starches, such as waxy cornstarch. Conditions under which starch is apparently debranched will be described in terms of screw design, screw speed and temperature conditions. In addition, hydrolysis of starch using common acids will be examined as another possibility for making starch more linear without the use of debranching enzymes. |