Moisture

Measuring moisture in the quality control laboratory and online in production is of utmost importance because moisture determines the efficiency of the different productions steps and therefore the quality of the final product. Also, the final moisture in the cigarette is an important quality parameter which, for example, determines the smoking characteristics and the colour of the cigarette provides valuable information for process control.

The Near Infrared Reflectance (NIR) technique is highly suitable for this purpose, but in the past the problem with the generally used reference method loss-on-drying (LOD) or “Oven Moisture” is that on the one hand the NIR Instruments presently in use only measure water in tobacco. On the other hand, water is not the only volatile component resident in tobacco: there are also a number of components present such as essential oils, humectants like propylene glycol and glycerin, volatile components of casings and flavours and the like. These components which are referred to in the literature as Total Volatile Organic Compounds (TVOC) are evaporated in the oven to a larger or lesser extent. The ratio between water and TVOC’s may change to a great extent mainly due to the variations of up to2 % in essential oils. The TVOC’s however, are not measured by conventional NIR instruments; therefore the NIR instruments have to be recalibrated against LOD to give the correct “Oven Moisture” value; and this may require many samples to be taken in order to compensate for these variations for every new batch of a blend.