Impact of the fungal protease produced by Fusarium culmorum on the protein quality and breadmaking properties of winter wheat

Abstract

Samples artificially infected by Fusarium culmorum were analyzed to assess the effects of Fusarium infection on the protein quality of winter wheat (Triticum aestivum L.). The Fusarium infection did not noticeably influence either the crude protein content or the water absorption ability of the wheat flour. The protease activity found in the wheat flour was inversely correlated to the sedimentation value. In contrast, it was positively correlated to both the free amino acid content and the degree of infection as expressed in Fusarium protein equivalents (FPE) quantified by an enzyme-linked immunosorbent assay. A distinct reduction in the content of both total glutenin and high molecular weight glutenin subunits was detected in the seriously infected samples (FPE>20 µg g⁻¹). The infection with Fusarium impaired the dough quality and led to a deformed loaf shape. The fungal protease was active over both a wide range of temperatures (from 10 to 100 °C) and a wide range of pH values (from 4.5 to 8.5). The maximum protease activity was displayed at 50 °C in the pH range 6.0–8.0. This property indicates that the protease produced by F. culmorum may impair storage proteins throughout all the processing procedures associated with wheat flour, thereby causing weak dough properties and, consequently, unsatisfactory bread quality.