EFFECT OF THE OUTER BRAN LAYERS ON THE LOAF VOLUME OF WHEAT BREAD

The effect of the outer bran layers of wheat on the breadmaking quality (loaf volume) of flour was studied by the abrasion (pearling) of wheat grain prior to milling. When the outer layers of six wheat grists with different wholemeal baking qualities were removed by pearling, only three of the grists produced loaves with significantly higher volumes than the corresponding controls. For the three grists giving an improvement in breadmaking quality, the average increase in volume was about 7·4%. The variation in the response to pearling may depend on the cultivars present, but not necessarily on the original breadmaking quality of the individual wheat grists. Bran materials collected from a sequential pearling process affected baking performance detrimentally when added to a wholemeal control of an unpearled grist and to a composite flour (i.e. a white flour plus 12·5% bran and offal). The most marked depression in loaf volume was observed when the outermost bran fraction (about 1·1 % of the grain weight), containing the highest concentration of epicarp hairs, was incorporated into the breadmaking recipe. Heat treatment (autoclaving) of this fraction did not diminish its adverse effect on loaf volume, suggesting that heatsensitive components (e.g. enzymes) are not implicated. Also, the differences in original unesterified free fatty acid levels between the white flour, the wholemeal and the flour from pearled grain were found to be small, and are unlikely to account for the observed differences in baking performance. Dry abrasion or pearling of the wheat grists is unlikely to improve the storage stability of the resulting flours, since the lipase activities of the wholemeal and the flour from pearled wheat were not significantly different. Microscopical examination of the wholemeal dough suggests that non-endosperm components induce serious structural distortion of gas cells and may contribute to the resultant crumb morphology, which is an important element of crumb texture. © 1992, Academic Press Limited. All rights reserved.