Miller Magazine Issue: 155 November 2022

76 COVER STORY MILLER / NOVEMBER 2022 The Falling Number Apparatus is difficult to master and the poor precision for most tests results in a broad range for determining low or high Amylase Activity. The question is whether NIR can be used to measure or estimate the Fall- ing Number Apparatus. There are no NIR absorption bands that correlate directly with Falling Number, however starch, protein and water contents will influence the viscosity of a water flour suspension and thereby should correlate to the Falling Number test. Many NIR instrument manufacturers sup- ply calibrations which include Falling Number, however the error of these NIR calibrations or methods can be quite large and should only be used a rough guide. Typically, a NIR cali- bration for Falling Number has a Standard Error of Prediction between 30 and 50 seconds. When the useable Falling Num- ber value for most wheat flour operation is greater than 250 seconds, the NIR calibration only provides a 95% confidence level between 190 and 310 seconds. IN LINE NIR ANALYSIS Near Infrared Spectroscopy lends itself to in line or contin- uous measurement of quality parameters because it is rapid and non-destructive. The challenge is how to capture the NIR spectra from a flowing stream of wheat, rice, corn, soybean, flour and meals. Figure 3 shows an in-line NIT analyser (CropScan 3000S In Line Analyser) installed in the intake silo of a flour mill in Australia. The analyser was originally developed for mea- suring whole grains in a combine harvester but has been adapted to the in-line measurement within the flour mill. As grain passes down a shute, it falls into the sample head of the CropScan 3000S where it is trapped for 3-5 seconds. A NIT scan is performed and the grain is released back into the stream of grains. The measurement of the NIR spectra are performed using a Silicon Diode Array Spectrometer and a Fibre Optic Cable to connect the Sample Head and the Spectrometer. Protein and Moisture readings are averaged for the load of grain that has been dumped into the receival silo and the data is displayed on the computer screen lo- cated in the mill laboratory. Figure 4 shows the plot of the Protein data from the CropScan 3000S compared with the laboratory’s benchtop NIR analyser (Foss Infratech 1241). In line analysis of the flour streams is also an established application for NIR. In this case Near Infrared Reflectance anal- ysers are used. Companies including Buhler, Buchii, Foss and Perten offer in line NIR analysers for measuring flour streams. Typically, these measurements are made through a window in a pipe or shute where the flour is moving past the NIR analy- ser. The major problem with such a setup is that the packing density of the flour varies. To improve the consistency of pre- sentation of the sample of flour to the analyser, various chokes and traps have been implemented. The best device is where the flour is trapped, compressed against the window and then released. Such a device introduces a mechanical element into the process stream however it does provide a more consistent and reliable measurements. There are several suppliers of grain colour sorting ma- chines, i.e., Satake, Buhler etc. These machines rapidly sort and segregate grains based on colour so that grains which are weather damaged, exhibit blacktip or are fungal stained, are rejected before milling. In line measurement of aleurone and bran specks in flour streams is also available, i.e., Bran- scan Flouroscan F4000, which uses UV fluorescence to de- tect these components that indicate the quality and purity of the flour or semolina. Moisture is very critical component in flour milling. Wheat is conditioned to 15-16% moisture and allowed to stand for many hours before milling. A NIR in line analyser was developed to measure the water content of wheat as it was being condi- tioned. The objective was to better control the final moisture content. The difficulty in making this measurement lies in that the water is not bound in the grain but lies on the outside of the grain until it is absorbed which takes many hours. Figure 3 CropScan 3000S In Line Sample Head Figure 4 Plot of Protein Prediction