Determination of starch by the amyloglucosidase method

Authors

• Maija-Liisa Salo Department of Animal Husbandry, University of Helsinki
• Marja Salmi Department of Animal Husbandry, University of Helsinki

DOI: https://doi.org/10.23986/afsci.71697

Abstract

A method of determining starch based on the use of amyloglucosidase is presented. In the method the sugars are extracted from the sample with 80 % ethanol, the starch is gelatinised by boiling with water for 10 minutes, after which it is hydrolysed into glucose by amyloglucosidase at pH 4.8 at 40°C (20—22 hours) or at 60°C (4—5 hours). The reducing sugars are determined. Purification of the solution for the sugar determination is not necessary for cereal products, peas and potatoes. For vegetables and legumes ionexchange purification reduces the results by 0—0.3 per cent units. The buffer concentration in the sugar determination should be less than 0.01 M. The method was found to give a 100 per cent result for pure starch preparations. The purity of the hydrolysates was examined by paper chromatography and it was observed that, at least for some materials poor in starch, the starch hydrolysate contains small amounts of other sugars besides glucose. However, with a short hydrolysing time these amount to only 0.2—0.3 % of the original dry matter. The repeatability of the method is good, 1—1 ½ %. The analysis of a series of 8—9 samples takes about 12 hours.