CONTINUOUS ACETIC-ACID POLYACRYLAMIDE-GEL ELECTROPHORESIS AS A TEST FOR DETECTION AND DETERMINATION OF COMMON WHEAT IN DURUM-WHEAT

A method was proposed to detect and determine the content of common wh eat in durum wheat. It is based upon the acetic acid polyacrylamid gel electrophoresis (PAGE) of gliadins. followed by the determination of the specific gliadin bands which are only present in common wheat. Gli adins were extracted with 70% ethanol from 27 durum and 33 common whea t cultivars collected from several sources as well as 96 blend prepare d by mixing 4 durum with 4 common wheat at 6 ratios. Durum wheat elect rophoretic patterns lack certain slow moving gliadin bands present in common wheat, but these bands can be detected in the samples of durum wheat mixed with common wheat. The densities of these bands are propor tional to the percentage of common wheat in the samples. Coomassie Blu e of these bands was extracted overnight with 25% pyridine in water an d the transmittance of the blue color was measured at 605 nm. There wa s a highly significant negative correlation between the transmittance values and the percentages of common wheat in durum wheat (r = -0.93* , n = 96). By this method, durum wheat or its semolina samples mixed with 10% common wheat or its flour could be visually detected from the electrophoregrams. Also one can compute the percentage of common whea t in a mix from the calibration curve.