Insight into variability of apparent endoxylanase and endoxylanase inhibitor levels in wheat kernels

The influence of wheat variety, harvest year and harvest date on the levels of wheat kernel-associated endogenous and microbial endoxylanases and wheat endogenous endoxylanase inhibitors was investigated using ten winter wheat varieties grown in 2002 and 2003. Three of the varieties were harvested on five different dates in a 1 month period spanning the optimal harvest period. Introductory experiments indicated that endoxylanase activity was very heterogeneously distributed among the different wheat kernels, necessitating the use of relatively large amounts of kernels, i.e. 100 g, to obtain representative wholemeal samples. Apparent endoxylanase activities in these samples largely depended on variety and weather conditions prior to harvesting. In contrast, apparent endoxylanase inhibitor levels were less dependent on climatological circumstances and were mainly determined by genetic factors. The data derived from this study may contribute to explaining the differences observed in functionality between wheats.