Development of rheological standards for whole wheat flour

Abstract

In Brazil, whole wheat flour is normally obtained by reincorporating wheat bran to refined wheat flour. Wheat bran has high contents of functional components (fibers, antioxidants, vitamins and minerals), concentrated in the external parts of the grain of wheat and related to many beneficial health effects. A great research field is centered in the development of cereal-based functional products with the addition of wheat bran. In breadmaking, the presence of the bran (and germ) fractions affects dough rheological properties, and consequently, alters important characteristics of the final product. The main changes caused by theses fractions rich in fibers and lipids in flour rheological properties evaluated by classical methodologies using apparatus such as the farinograph, the extensigraph and the alveograph, are the increase of water absorption, dough development time, mixing tolerance index and resistance to extension; and the decrease of extensibility. However, in the final product, bran incorporation results in the reduction of specific volume, increase in crumb firmness, darkening of the product and alterations in sensory properties. It is verified that it is not possible to use, for whole wheat flour, the same rheological standards used to classify refined wheat flour, as for the latter the consistency of the dough evaluated is related to the viscoelastic characteristics of the gluten network, while in whole wheat flour doughs, fibers affect consistency, without being related to protein quality. Researchers in cereal science and technology, the bakery industry, artisan bakeries and wheat flour mills have difficulties in classifying whole wheat flours to indicate their application in breadmaking. The greatest problem resides in the lack of correlation between the commonly used rheological parameters of these flours and the technological quality characteristics of the final products. The development of rheological standards for whole wheat flour is necessary to ensure proper use of flours with wheat bran incorporation, to minimize the current deficiencies observed. (AU)