3.1.4 Recommended equipment for measuring aw
Many methods and instruments are available for laboratory measurement of water activity in foods. Methods are based on the colligative properties of solutions. Water activity can be estimated by measuring the following:
• Vapour pressure
• Osmotic pressure
• Freezing point depression of a liquid
• Equilibrium relative humidity of a liquid or solid
• Boiling point elevation
• Dew point and wet bulb depression
• Suction potential, or by using the isopiestic method
• Bithermal equilibrium
• Electric hygrometers
• Hair hygrometers