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Determination of mineral content of flour and semolina by modified conductometric method

Conductometric determination of ash content (ICC Standard No. 157), based on the measuring of electrical conductivity in the flour extract, takes less time and is cheaper than a common standard combustion method (ICC Standard No. 104/1). However, for industrial purposes, conductometric method still takes too much time, because the procedure includes extraction of flour-water suspension at 30 °C for one hour followed by centrifugation. Therefore, the aim of this work was to simplify and shorten conductometric method. The effect of a shorter extraction time and the influence of electrical conductivity measurements directly in flour-water suspension at room temperature (without previous centrifugation) were analyzed. Samples of wheat flour with the ash content ranging from 0, 403-1, 498% were tested. The ash contents were predicted by measuring electric conductivity in the flour-water suspensions every 10 minutes and results were compared with the results obtained with the standard combustion method. In addition to that, influence of flour particle size was also studied with samples of semolina of different particle size. The obtained results showed that electric conductivity measurements can provide high precision results of flour ash content even if analysis were carried out directly in flour-water suspension at room temperature for only 30 minutes (without previous centrifugation). Extraction time and calibration curve should be modified if method is applied on semolina with larger particle size. Therefore, this modification of conductometric method could have an excellent application in cases when it is necessary to have rapid feedback of the ash content in wheat flour.

wheat flour mineral content; electrical conductivity; conductometric method

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