[The behaviour of the microflora of wheat related to the cleaning- and the flour mill-flow diagram. IV. Communication: Investigations regarding the behaviour of the microflora during the cleaning and milling of grain (author's transl)].

For the production of certain foodstuffs and preparations of foodstuffs the use of mill products with low microbial germ content is necessary. The demands for microorganisms, in relation to species and number which can be tolerated, depend on the kind of the foodstuff, produced from the milled product. Investigations were done to get milled products with low microbial content; the effect of cleaning and "fractionated" milling of the grain was studied. Flours with a low ash content (flour-type 405 until 550) show generally a low microbial content. More milling-technical problems arise for the production of flours with a high content and a low microbial germ content. The main factors are selection of raw materials, separation of kernels with large-size grains (about 20 till 30%) and an additional surface treatment of the kernels. Whole meal products which are consumed by the customer without preliminary heating, should be also produced from kernels with large size after an intensive surface treatment of the kernels. Food bran should be only produced from grain after a surface treatment. A considerable part of the microflora in the outside layer of the kernels is separated by this particular cleaning method. In the bran from middlings the microflora of the grain concentrates very much. Within the break-passages of the milling diagram a separation should be done in coarse and fine hulls. To improve the demonstrated effects it is necessary to eliminate all the contamination sources during cleaning. The risk of a contamination of milled products with fungi during the milling process is obviously very different. To eliminate this contamination source a detailed analysis is necessary.