World Grains Summit: Foods and Beverages location:San Fransisco, California, USA date:17-20 September 2006
Endoxylanases (EXs) are enzymes which hydrolyze the backbone of cell wall arabinoxylans and which, in doing so, can have a significant impact on cereal based processes and end products. The EXs associated with wheat kernels consist of wheat endogenous EXs and kernel associated microbial EXs. As assessment of the presence of these EXs can be significantly hampered by the presence in wheat of high levels of endogenous EX inhibitors, it is likely that the importance of wheat kernel associated EXs in cereal processing and in year-to-year wheat quality variation has been persistently underestimated. To substantiate this hypothesis, an extensive washing procedure was developed which provided near quantitative separation of the microbial EXs located on the surface of wheat kernels from the endogenous EXs and EX inhibitors located in such kernels. The EX activity in the washing liquid, shown to correspond to the microbial EXs, and the washed kernels, shown to correspond to the endogenous EXs, allowed estimation of the total EX activities associated with wheat. Using the developed procedure on 3 wheat varieties, it became clear that microbial EXs can account for over 90% of the total wheat associated EX activity and that the latter can be at least 5 times higher than apparent EX activity. In addition, it became clear that the total wheat kernel associated EX activities were of the same order of magnitude as the EX activities commonly added to wheat flour in bread making. In conclusion, the results of this study indicate that wheat kernel associated EX levels are underestimated when using standard EX determination methods. A more correct EX activity determination will allow to better assess the contribution of EX to wheat quality variation.