Evaluation of starch analysis methods for feed samples

The objectives of this work were to evaluate the efficacies of commercial s tarch analyses and of starch analysis extraction and gelatinisation procedu res. 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 w ith recoveries of purified starch of 92g kg(-1) or less. Three and four lab oratories had inflated values when samples contained glucose or sucrose, re spectively. Analyses appeared to have good specificity for glucose. Incompl eteness of starch detection and interference by non-starch carbohydrates ca n 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-mlolecular-weight carbohydrates, and gelatinisation with heat, alkali (KOH), 6M urea or 8M urea were evaluated. Extraction with 80EtOH or 90EtOH reduced interference from non-starch carbohydrates. Gelatinisation with hea t was adequate for good recoveries of starch glucose for both control (non- extracted) and 80EtOH-extracted samples; gelatinisation with alkali was req uired 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 remo val of low-molecular-weight carbohydrates is desired. (C) 2000 Society of C hemical Industry.