A critical examination of the sodium dodecyl sulfate (SDS) sedimentation test for wheat meals

Abstract

Sedimentation tests have long been used to characterise wheat flours and meals with the aim of predicting processing and end-product qualities. However, the use of the sodium dodecyl sulfate (SDS) sedimentation test for durum wheat (AACC International Approved Method 56–70) has not been characterised for hexaploid wheat varieties with a diverse range of protein quality and quantity. This paper reports the variation associated with important method parameters: sample weight, SDS concentration, technician, grinder and screen aperture (particle size). Sedimentation volumes were recorded every 5 min for 30 min and expressed as specific volume, i.e. sediment volume in mL g−1 meal. Ten diverse hexaploid wheat samples of markedly different protein quality and quantity were examined. The SDS sedimentation assay was shown to be highly robust and reproducible, with ANOVA (analysis of variance) model R2 values greater than 0.98 (individual time points). The procedure delineated soft and hard hexaploid wheat samples based on a combination of protein quantity and quality. Sample weight (if corrected to unit weight basis), recording time of at least 10 min, SDS stock concentration of at least 10 g L−1 (final), grinder type and screen aperture were minor sources of variation in SDS sedimentation volume relative to the effects due to differences among wheat samples. Interactions among ANOVA model terms were of relatively minor importance. Published in 2007 by This article is a US Government work and is in the public domain in the USA.