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Procedure for Obtaining Stable Protein Extracts of Cereal Flour and Whole Meal for Size-Exclusion HPLC Analysis

¹CSIRO Plant Industry, Grain Quality Research Laboratory, P.O.Box 7, North Ryde, NSW, 1670, Australia. ²Unidad de Genetica, Escuela Tecnica Superior de Ingenieros Agronomos, Universidad Politecnica, Ciudad Universitaria, E- 28040 Madrid, Spain. ³Present address: Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506-2201. ⁴Corresponding author. Email: larroque@pi.csiro.au

Experiments were conducted to determine the extent of instability of size-exclusion HPLC extracts prepared from flour, semolina, or whole meal. Procedures to obtain stable extracts were investigated. Whole meal extracts of durum wheat and triticale were the most unstable samples, whereas bread wheat showed smaller changes. Samples prepared from crushed maturing grains, especially during early stages, were greatly influenced by the instability process. By using protease inhibitors, evidence was obtained that endogenous proteases were the source of the instability. Reproducible peak 1 (polymeric protein) results were obtained for a period of at least 72 hr after extract preparation if protein extracts were heated for 2 min at 80°C in a water bath immediately after filtration into the sample vials and before SE-HPLC analysis. This treatment is a viable solution to avoid sample instability in whole meal and developing grain extracts, particularly when large sample sets are prepared for automatic injection into the HPLC.