A new study has shown that rye or wheat bran fortified breads treated with a particular xylanase can yield good quality breads with a prebiotic effect.
There is an increasing demand for fibre enriched breads, driven by the rising awareness among consumers that dietary fibre has beneficial effects on health and wellbeing.
Multiple studies have revealed the prebiotic activity of cereal derived arabinoxylan oligosaccharides (AXOS). Since AXOS exert prebiotic effects, Belgian-based researchers looked at whether it was feasible to produce good quality breads enriched with fibre, containing significant levels of these prebiotics.
Writing in the journal Food Chemistry, the food scientists report that, considering the average European daily bread intake (178 g), over 2.4 grams of AXOS would be consumed in whole meal as well as in rye bran fortified breads prepared with the xylanase H. jecorina.
“Such AXOS levels have been shown to provoke a prebiotic effect in a clinical trial with healthy volunteers,” they add.
The authors claim that the bread making process offers an unique opportunity to introduce AXOS in the diet since AX are naturally present in the traditional bread raw materials and xylanases are already used in bread making.
However, from a technical point of view, the incorporation of fibre in bread is a challenging task, said the researchers.
“Many authors reported that high fibre levels have a particularly detrimental impact on bread making and bread quality, among which impairment of the loaf volume appears to be the most important one,” they continued.
Much of the undesirable effects are ascribed to the characteristic rigid structure of insoluble fibre fractions, which hinders proper dough formation and bread development.
The researchers evaluated the AXOS producing capacity of different xylanases in whole meal bread making, looking at mesophilic xylanases originating from Bacillus subtilis, Aspergillus niger and Hypocrea jecorina, and one thermophilic xylanase from H. jecorina (HjXynA).
They applied these at different dosages. “At dosages that did not impair dough manageability, HjXynA solubilised and cleaved the arabinoxylan fraction to the largest extent, resulting in an AXOS content of 2.1 per cent (dry basis) and an average degree of polymerization (avDP) of 9,” they found.
In the second part of their study, the impact of HjXynA on the AXOS levels in dietary fibre enriched breads was investigated. Rye or wheat bran fortified breads treated with HjXynA yielded good quality breads with AXOS levels above 2 per cent with an avDP of 26 and 19, respectively, reported the team.
The authors concluded that the use of a thermophilic xylanase gives optimum results, as it generates high AXOS levels, most likely “due to prolonged activity during the baking phase, while having limited impact on dough stickiness during the kneading and leavening phases.”
The authors said that the study was carried out as part of the K.U. Leuven Methusalem programme Food for the Future.
Source: Food Chemistry
Published online ahead of print: doi: 10.1016/j.foodchem.2011.08.043
Title: Xylanase-mediated in situ production of arabinoxylan oligosaccharides with prebiotic potential in whole meal breads and breads enriched with arabinoxylan rich materials
Authors: Damen, B., Pollet, A., Dornez, E., Broekaert, W.F., Van Haesendonck, I., Trogh, I., Arnaut, F., Delcour, J.A., Courtin, C.M.