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Partial Purification of a Water-Extractable Rye (Secale cereale) Protein Capable of Improving the Quality of Wheat Bread¹

¹Contribution No. 97-457-J. Kansas Agricultural Experiment Station. Department of Grain Science and Industry, Manhattan, KS 66506. ²Laboratory of Food Chemistry, Katholieke Universiteit Leaven, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium. ³Research associate and professor, Department of Grain Science and Industry, Kansas State University, Manhattan KS 66506. ⁴Present address: American Institute of Baking, 1213 Bakers Way, Manhattan, KS 66502. ⁵Present address: R & R Research Services, Inc., 8831 Quail Lane, Manhattan, KS 66502. ⁶Corresponding author. E-mail: r_and_r@kansas.net

Rye water-soluble extracts contain a protein fraction that, when added at low concentrations to a straight-dough breadmaking recipe, significantly increased bread volume. Enrichment of the active component is possible by anion-exchange fractionation with diethylaminoethyl-cellulose (DEAE), by ammonium sulfate precipitation, or by using rye bran or shorts milling fractions as the starting material. The active material was not bound to DEAE-cellulose. With ammonium sulfate precipitation, the fractions obtained at 30, 40, and 50% saturation were active in straightdough baking experiments. Iso-electric focusing revealed that fractions active in breadmaking invariably contained alkaline protein fractions (pI > 7.5). Inactivation of enzyme material by boiling the water-soluble extract from rye destroyed all breadmaking activity. The activity of the bread improver was additive to that of potassium bromate but not to that of ascorbic acid. It was not counteracted by catalase, showing that it does not work by a mechanism involving the production of hydrogen peroxide. The extract was not able to overcome the detrimental effect on bread quality resulting from mixing dough in a nitrogen atmosphere.