Properties of damaged starch granules: I. Comparison of a micromethod for the enzymic determination of damaged starch with the standard AACC and Farrand methods

Karkalas, J.; Tester, R.F.; Morrison, W.R.

Journal of Cereal Science 16(3): 237-251

1992


ISSN/ISBN: 0733-5210
DOI: 10.1016/s0733-5210(09)80087-8
Accession: 009259684

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Abstract
An enzymic colorimetric micromethod for the determination of damaged starch in samples weighing 50 mg was used. Oligosaccharides in filtered fungal alpha-amylase digests of damaged granules were hydrolysed with amyloglucosidase to yield glucose which was measured with a glucose oxidase-peroxidase-chromogen reagent. Sixteen manual determinations were performed in 3 h, or 32 determinations in 3h if automated flow injection analysis of the digests was used. A comparative study of the American Association of Cereal Chemists (AACC) and the Farrand methods, both of which determine damaged starch as reducing sugars by non-specific methods, provided evidence that the AACC method overestimates damaged and gelatinized starch by about 30% (alpha-glucan basis), while the Farrand method gives corresponding values which are about three times greater. These methods quantify, as 'maltose', only 64-70% of the starch digested by alpha-amylase, and substantial correction factors are then used to calculate the total damaged starch content. Since amylose complexed with endogenous lipids of cereal starches is not digested by fungal alpha-amylase, a small correction factor should be used for damaged or gelatinized cereal starches; no correction is required for the lipid-free waxy cereal starches and non-cereal starches. The micromethod can also used to quantify gelatinized starch in processed cereal foods.