Evaluation of starch analysis methods for feed samples

Abstract

The objectives of this work were to evaluate the efficacies of commercial starch analyses and of starch analysis extraction and gelatinisation procedures. In Study 1, accuracy and specificity of commercially available starch analyses were evaluated with six co-operating laboratories (five commercial, one university). Results from 11 test samples showed three laboratories with recoveries of purified starch of 92 g kg−1 or less. Three and four laboratories had inflated values when samples contained glucose or sucrose, respectively. Analyses appeared to have good specificity for glucose. Incompleteness of starch detection and interference by non-starch carbohydrates can affect commercially available analyses. In Study 2, extraction with 80:20 ethanol/water (v/v; 80EtOH) or 90:10 ethanol/water (v/v; 90EtOH) to remove low-molecular-weight carbohydrates, and gelatinisation with heat, alkali (KOH), 6 M urea or 8 M urea were evaluated. Extraction with 80EtOH or 90EtOH reduced interference from non-starch carbohydrates. Gelatinisation with heat was adequate for good recoveries of starch glucose for both control (non-extracted) and 80EtOH-extracted samples; gelatinisation with alkali was required for 90EtOH-extracted samples. Recoveries of pure starch samples were greatest with no extraction and heat gelatinisation. 80EtOH extraction with heat gelatinisation appears to be an adequate preparation method when removal of low-molecular-weight carbohydrates is desired. © 2000 Society of Chemical Industry