Publication no. C-2003-1215-04R |  VIEW ARTICLE

Degradation of HMW Glutenins During Wheat Sourdough Fermentations.

Jussi Loponen (1,2), Markku Mikola (3), Kati Katina (4), Tuula Sontag-Strohm (1), and Hannu Salovaara (1). (1) Department of Food Technology, University of Helsinki, POB 27, FIN-00014 University of Helsinki, Finland. (2) Corresponding author. E-mail: <jussi.loponen@helsinki.fi> (3) Suomen Viljava Oy, Finn Cereal, Kielotie 5 B, 01300 Vantaa, Finland. (4) VTT Biotechnology POB 1500, FIN-02044 VTT, Finland. Cereal Chem. 81(1):87-93. Accepted July 31, 2003. Copyright 2004 American Association of Cereal Chemists, Inc.

Bakeries use sourdoughs to improve bread properties such as flavor and shelf life. The degradation of gluten proteins during fermentation may, however, crucially alter the gluten network formation. We observed changes that occurred in the HMW glutenins during wheat sourdough fermentations. As fermentation starters, we used either rye sourdough or pure cultures of lactobacilli and yeast. In addition, we incubated wheat flour (WF) in the presence of antibiotics under different pH conditions. The proteolytic activities of cereal and sourdough-derived proteinases were studied with edestin and casein. During sourdough fermentations, most of the highly polymerized HMW glutenins degraded. A new area of alcohol-soluble proteins (approximately 30.000 MW) appeared as a result of the proteolytic breakdown of gluten proteins. Very similar changes were observable as WF was incubated in the presence of antibiotics at pH 3.7. Cereal and sourdough-derived proteinases hydrolyzed edestin at pH 3.5 but showed no activity at pH 5.5. An aspartic proteinase inhibitor (pepstatin A) arrested 88-100% of the activities of sourdough enzymes. According to these results, the most active proteinases in wheat sourdoughs were the cereal aspartic proteinases. Acidic conditions present in sourdoughs create an ideal environment for cereal aspartic proteinases to be active against gluten proteins.