A CRITICAL EXAMINATION OF THE SODIUM DODECYL SULFATE (SDS) SEDIMENTATION TEST FOR WHEAT MEALS

Authors: Morris, Craig; Paszczynska, Bozena; Bettge, Arthur; KING, G - WASHINGTON STATE UNIV

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2006
Publication Date: 1/24/2007
Citation: Morris, C.F., Paszczynska, B.J., Bettge, A.D., King, G.E. 2007. A critical examination of the sodium dodecyl sulfate (sds) sedimentation test for wheat meals. Journal of the Science of Food and Agriculture 87:607-615.

Interpretive Summary: Rapid predictive tests have long been used to define the potential end-use quality of wheat meals and wheat flours. One of the predictive tests that has been used successfully for durum wheat (primarily employed as the base ingredient for pasta products) is AACC International Approved Method 56-70: Sodium Dodecyl Sulfate (SDS) Sedimentation Test. This test has not been examined scientifically to determine its efficacy for use in hexaploid wheats (wheats that are used for breads, cookies, cakes, noodles; essentially all products that are “not pasta”). This research examines the results of the SDS Sedimentation in hexaploid wheats that represented a wide range of hardness, protein content and end-use quality. The experimental variables: sample weight, SDS concentration, operator, grinder type and wheat meal particle size were statistically analyzed. The sedimentation values were shown to be very reproducible. Further, delineation among samples for hardness, protein quantity and protein quality was achieved. Sample weight (corrected to a constant basis), settling time of at least 10 minutes, SDS concentration of at least 1%, particle size and grinder type were all minor sources of variation when compared to the differences among wheat samples (wheat class, protein quantity and protein quality). The results imply that the chemistry of the method provides the possibility of using the SDS sedimentation test to examine rapidly the potential end-use quality of hexaploid wheat.

Technical Abstract: Sedimentation tests have long been used to characterize 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 AACC International Approved Method 56-70 for durum wheat has not been characterized for hexaploid wheat varieties with a diverse range of protein quality and quantity. Here we report the variation associated with important method parameters: sample weight and SDS concentration, technician, and grinder and screen aperture (particle size). Sedimentation volumes were recorded every 5 min for 30 min and expressed as specific volume, that is, sediment volume in milliliters per unit gram of 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 model R2’s of > 0.98 (individual time points). The procedure delineated the 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), and grinder type and screen aperture were minor sources of variation on SDS sedimentation volume relative to the effects due to differences amongst wheat samples. Interactions among ANOVA model terms were of relatively minor importance.