Starch

We feel that a more useful and practical solution at present is to use the terms starch and dietary fiber separately. An appropriate definition of starch follows: "Starch is a large polymer of glucose consisting of glucose units formed into unbranched amylose chains composed of alpha-1,4 linked glucose residues and highly branched amylopectin with alpha-1,4 and alpha-1,6 bonds." There are several methods to measure starch (4-9). There are commercially available kits to measure starch based on converting it to soluble fragments with minimal production of glucose followed by quantitative hydrolysis by amyloglucosidase (4). (This kit can also provide an estimation of enzyme-"resistant" starch). In the method for total starch, starch is solubilized with DMSO or the sample is cooked in buffer with a thermostable alpha-amylase. Complete breakdown to dextrins is carried out by subsequent treatment with the de-branching enzyme pullulanase in combination with alpha-amylase to minimize the amount of free glucose formed by continued action of alpha-amylase. Quantitative hydrolysis of the resulting maltotrioses and maltoses, (which are not substrates for the bacterial alpha-amylase) to glucose is carried out with amyloglucosidase and glucose is measured using a standard enzyme/color reaction with samples read in a spectro-photometer. Unlike the term "complex carbohydrates", starch is a more defined chemical entity and can be measured by several methods.

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