Search: infrared drying

The classic procedure performed using a drying oven is very time-consuming. Drying with infrared radiation significantly shortens the time required for drying, since the barley to be dried is immediately penetrated by the infrared radiation, which gives off a part of its energy, thereby heating the barley. With infrared drying, an adjustable heat source is connected to an electronic balance. The loss in mass during drying is continually recorded by the balance. The apparatus is equipped with a built-in microprocessor, which allows it to be programmed with data which was collected empirically with regard to optimal drying conditions.

Determination of the moisture content of barley is carried out according to ISO 712, 2009, i.e., milled barley is dried at a defined temperature within a set time period in an electrically heated air-drying oven.

The moisture content is calculated through the difference in mass prior to and after drying.

Barley with moisture contents above 17 % must be pre-dried as whole kernels prior to analysis. This method is not suitable for malt.

The sample is heated directly on the weighing pan in the drying chamber using microwaves. The water evaporates and is removed by a compressor. In order to avoid disturbing the weighing process as little as possible, the sample is protected from the flow of gas by a porous cover. The change in weight is measured directly; after a constant weight is reached, it is evaluated.

With microwave-vacuum drying, the vaporization temperature is lowered, resulting in a more gentle drying process. Additionally, the samples are under constant rotation to prevent degradation and burning of the sample.

Reflectance spectroscopy in the near-infrared spectral range (NIR) is employed as a physical method for the determination of substances found in grain. This method is based on the fact that different substances, e.g., proteins, in wavelengths ranging from approximately 800 to 2500 nm possess characteristic absorbance and reflection spectra.

Light of a defined wavelength is directed towards the (finely ground) sample in a measurement chamber and is reflected diffusely back to a detector, which measures the intensity of the reflected light. On the basis of the absorbance measured, an integrated computer calculates the protein content of the sample. In order to be able to perform these calculations, the NIR spectrometer must be specifically calibrated for each product (e.g., barley, wheat, barley malt, wheat malt) as well as for each constituent (in this case, protein). The calibration is carried out with data gathered from the absorbance of spectra from reference substances. The protein content of individual samples is determined chemically using a reference method, for example, with the Kjeldahl method and are then correlated with the respective spectral data. Through comparison of the spectra from the analysis sample with the reference sample used in the calibration, the protein content is determined. Since seasonal differences in barley kernels from year to year make it necessary to modify the spectral data so that they match the chemically determined data, calibration must be monitored and adjusted accordingly. Normally, the manufacturer supplies a standard calibration reference with the device.

The primary advantages offered by this method are the speed with which samples are analyzed (< 1 min per sample) and the fact that no chemicals are necessary. Grinding the sample at a defined setting prior to the analysis may be required; however, it is not necessary to weigh the sample. With the latest generation of NIR devices, samples no longer need to be ground. The accuracy of the measured values is dependent upon the quality of the calibration. If analysis is performed carefully, standard deviations of 0.1 % are attainable.

In contrast to the NIR method, the more recently developed NIT method measures the light passing through the samples. This technique requires no pretreatment of the samples, thus eliminating a major source of error. The large sample size, approx. 500 g, makes highly precise measurements possible. Measurements are usually made in the wavelength range of 850−1100 nm.

Calibration and the calculations for determining the amounts of the various constituents are both performed in the same way as in the NIR method. Special software for personal computers can be employed to create the calibration data, which uses the data structure generated and stored in the NIT device as a basis for the calculations. The advantages offered by this method are the rapidity of the analysis (approx. 45 s per sample) and the absence of chemicals.