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Water Activity Meter


Water Activity Meter is defined as the current volume and availability of free water in a sample and should not be directly compared with the water content (g water/ g substance). The water activity is given as the aW value and ranges between 0 (absolute dryness) and 1 (condensed humidity). Only this component can possibly form the ideal medium for microbiological growth on the surface which influences the microbiological stability. Free water in products is jointly responsible for the growth of undesirable organisms such as bacteria or fungi, which produce toxins or other harmful substances. For the determination of the a W-value the relative humidity in the surrounding air over the sample is measured. It is proportional to the a W-value. A meaningful a W-measurement can only be done if the sample shows a constant temperature during the measurement. The relative equilibrium humidity of a product, which is ascertained through its partial pressure of water vapor on the surface, depends on the chemical compound, temperature, water content, storage environment, absolute pressure and packing. Lab Master-aW is a high-quality laboratory device for the high precision determination of the aw-value of food, pharmaceutics, cosmetic etc.. Features: - High accuracy and repeatability - Temperature controlled measuring chamber - Increased measurement speed - Measurement cell with saved calibration data - Intuitive and simple menu navigation - Modular expandability to multi channel system Chemical/Biochemical effects of high/low aw value are: Microbiological stability (growth) Chemical stability (see table) Content of proteins and vitamins Colour, taste and nutritional value Stability of the compound and durability Storage and packing Sorption isotherm The relation b/w water content and water activity is showing the sorption isotherm of a product. Change in Temp will vary the aw-value at each humidity point