A comparision of methods to quantify prolamin contents in cereals

Hydrophobic prolamins are endosperm storage\r\nproteins accounting for about 40% of the\r\ntotal protein in most cereal seeds. Despite the\r\nabsence of a reference method, several procedures\r\nhave been periodically published to\r\nquantify prolamins in cereals. The aim of this\r\nstudy was to compare a conventional fractionation\r\nassay (LND) vs three other methods: one\r\nbased on sequential extractions (HAM) and\r\ntwo rapid turbidimetric procedures (L&H and\r\nDRO). Prolamins were extracted in duplicate\r\non barley, corn and wheat samples. For the turbidimetric\r\nprolamin evaluation in barley and\r\nwheat, a universally available purified gliadin,\r\nas alternative to purified zein, was also tested\r\nas standard reference material (SRM). The\r\nextraction prolamin values were different\r\namong grain types (P<0.01) and methods\r\n(P<0.01) without interaction (P>0.05). LND\r\nagreed sufficiently well both with HAM and\r\nwith L&H methods (R2=0.664 and R2=0.703,\r\nrespectively, P<0.01). On all tested cereals,\r\nLND and L&H gave similar prolamin extraction\r\nvalues (P>0.05), whereas a higher prolamin\r\nquantification was obtained using HAM\r\n(P<0.05). Overall, DRO did not provide similar\r\ncomparison and performance parameters with\r\nrespect to other method comparisons. The\r\neffect of changing purified zein with purified\r\ngliadin was noteworthy only for L&H, both for\r\nwheat and barley samples (P<0.01).\r\nConsidering the increasing attention of animal\r\nnutritionists on prolamins, our results\r\ncould get useful information for routine laboratory\r\nanalysis.