What is monolayer water activity?

What is monolayer water activity?

Up to a water activity of about 0.30 water is considered to be held on polar sites of relatively high energies (Figure 1.5. 1). This is called the monolayer. The aw in the range of 0.30 to 0.70 is referred to as multilayer water.

How is moisture sorption isotherm calculated?

More modern isotherms showing the sorption of water vapor, on the vertical axis, provide the ratio of the weight of water adsorbed divided by its dry weight , or that ratio converted into a percentage. On the horizontal axis they provide relative humidity or water activity of the air presented to the material.

What is monolayer value?

The value of the monolayer (M0) is of particular importance because it indicates the amount of water that is strongly adsorbed in specific sites, and it is considered to be the value at which a food product is the most stable.

What does a moisture sorption isotherm show?

A moisture sorption isotherm is a graph showing how water activity (aw) changes as water is adsorbed into and desorbed from a product held at constant temperature. Water activity almost always increases as moisture content increases, but the relationship is not linear.

What is GAB model?

The GAB (Guggenheim–Anderson–de Boer) and BET (Brunauer–Emmett–Teller) are the most common models used for the determination of the sorption isotherms for different materials. The GAB model is represented by constant C and K. Constant C is a positive value that represents the total heat of the first layer of sorption.

What are isotherm models?

Adsorption isotherm models can provide mechanism information of the adsorption process, which is important for the design of adsorption system. However, the classification, physical meaning, application and solving method of the isotherms have not been systematical analyzed and summarized.

What is isotherm line?

Isotherm, line drawn on a map or chart joining points with the same temperature. Isotherms are commonly used in meteorology to show the distribution of temperature at the Earth’s surface or on a chart indicating constant level or constant pressure.

How do you calculate Langmuir isotherm?

ce/qe = 1/qm KL + ce/qm , where ce is the equilibrium concentration of the adsorbate and qe is the adsorption capacity adsorbed at equilibrium, qm is maximum adsorption capacity and KL is the Langmuir adsorption constant.

What are lines of equal depth called?

Isobath. A line representing points of equal depth under water.