AACC International Annual Meeting location:Honolulu, Hawaii, USA date:21-24 September 2008
Arabinoxylan is only a minor constituent in wheat. Nevertheless, it can have a determining impact on wheat processing or on final product yield or quality, hence the use of xylanases to optimize wheat applications. In the last 20 years knowledge on xylanase functionality has been gradually building up. The presence and impact of wheat kernel associated xylanases has, however, largely been overlooked and was the object of several studies. Results of these studies indicated that xylanases associated with wheat kernels consist of wheat endogenous xylanases on one hand and kernel-associated microbial endoxylanases on the other hand. Levels and ratios between different types of enzymes were shown to vary significantly with harvest year and wheat variety. In some cases, wheat kernel-associated microbial endoxylanases accounted for over 90% of the total wheat-associated xylanase activity. The impact of these xylanases on two systems, i.e. refrigerated doughs subjected to longer term storage and wheat bread doughs subjected to a normal fermentation process, was investigated. Using debranning as a tool to remove the majority of kernel-associated microbial xylanases prior to milling, we were able to show that the onset and extent of dough syruping (the undesirable appearance of a brown liquid) during refrigerated dough storage was drastically reduced when using flour samples which contained reduced levels of xylanases. In normal bread doughs, mainly inhibition insensitive endogenous xylanases were active, and led to increased solubilization of arabinoxylan in the dough, probably affecting the end product. In conclusion, we can say that wheat kernel associated xylanases should not be neglected and that they can add to batch to batch and year to year variability in performance of wheat.