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Measuring flour moisture content using NM2.2 spectral module

Published 18.11.2016

The content of the flour can vary considerably in its protein quality, protein quantity, ash, moisture, enzymatic activity, color, and physical properties when obtained from different sources. The purpose of the flour measurements is to detect specific properties or characteristics of a flour such as moisture. The results of these measurements affect flour’s performance in food industry, and therefore these quality variations of the flour composition need to be detected. The Near-infrared spectroscopy (NIR) method of estimating protein and moisture contents is widely used in the milling and baking industries. NIR devices are easy to use, generate instant results, and can be operated by non-technical personnel. The method’s accuracy is dependent upon its calibration but the procedure for carrying out an analysis is quite simple.

We measured wheat flour samples with varying amounts of moisture with our NM module. NM-series is a new compact and powerful tool for realizing Near Infrared (NIR) spectroscopic measurement applications between 1350 and 2150 nm. In our measurements, the reference method for moisture was the oven-drying method which is sufficiently accurate for the routine analysis of flour moisture for example at the flour mill or bakery.

Results
The measurement results show that NM2.2 spectral module fitted with the Reflectance Optics accessory is optimal for the measurement of the flour moisture. The moisture content of the flour is important for two reasons. First, the higher the moisture content, the lower the amount of dry solids in the flour. Flour specifications usually limit the flour moisture to 14% or less. It is in the miller’s interest to hold the moisture as close to 14% as possible. Secondly, flour with greater than 14% moisture is not stable at room temperature. Biological activity at high moisture levels produces off odors and flavors in the flour.

For the 0 to 10 % moisture range the RMSECV (Root Mean Square Error of Cross Validation, 2sigma) value is approximately 0.50 %. This error might be even smaller if a larger sample set was to be used for the calibration. The measurement and analysis could be very fast if the wavelength vector and other measurement parameters were to be optimized, taking only a few second after starting the measurement. The maximum measurable moisture level with NM2.2 is likely between 20 and 25 %. NM1.7 is a good choice for measurement of moisture values higher than this.