The debranning of common wheat (Triticum aestivum L.) with innovative abrasive rolls

The physical and chemical modifications associated with the debranning of common wheat (Triticum aestivum L.) and the improvement of the hygienic characteristics of the kernels were examined. A pilot-plant debranning machine was equipped with rolls lined with synthetic diamond powder, an innovative abrasive material. The technological parameters taken into account were: the particle size of the abrasive elements, the processing time, the number of debranning passages and the hydration conditions of the kernels before treatment. The abrasive effects were observed by Scanning Electron Microscopy and quantified by evaluating the debranning level and several chemical and physical indices of kernels and waste. A preliminary hydration passage was determinant for reducing kernel breakage during debranning. Best results in terms of homogeneous removal of bran layers were obtained with the addition of 3% water and keeping the hydrated mass mixing for 5 min. Abrasive surfaces with fine particle size (<1000 mesh) gave a quite uniform debranning process, without deep grooves in the endosperm region. A final brushing of the debranned kernels assured a more accurate removal of bran layers. Debranning levels lower than 8–10% guaranteed low starch losses in the waste and, at the same time, noticeably reduced the microbial contamination of the kernels.