What is hysteresis in moisture?

What is hysteresis in moisture?

Hysteresis in foods is the phenomenon by which at constant water activity (Aw) and temperature, a food adsorbs a smaller amount of water during adsorption than during a subsequent desorption process. Current explanation (Caurie, 2007) states that sites adsorb moisture appropriate to their surface energies.

What is hysteresis in wood?

Like most other porous materials, wood exhibits sorption hysteresis. That is, the moisture content is higher if equilibrium is reached by desorption than if it is reached by absorption under the same ambient climate conditions.

What is hysteresis in moisture absorption?

The amount of moisture adsorbed by the material is dependent on the relative humidity of air to which it is exposed or to the avail- ability of water. This phenomenon, called hysteresis between the adsorption and desorption curves, is rarely considered during modeling or experimental studies of the building envelope.

What is hysteresis in adsorption?

Hysteresis has been observed in adsorption isotherms for a number of gas-solid systems and, generally, is attributed to adsorption in mesoporous materials with capillary condensation. It is shown that there can be phase transitions in the adsorbed phase which lead to hysteresis in kinetically controlled experiments.

What is the difference between water activity and moisture content?

Moisture content defines the amount of water in your food and ingredients, but water activity explains how the water in your food will react with microorganisms. The higher the water activity, the faster microorganisms like bacteria, yeast, and mold will be able to grow – resulting in higher standards of food storage.

What is the principle of moisture content?

The principle of the thermogravimetric method of moisture content determination is defined as the weight loss of mass that occurs as the material is heated. The sample weight is taken prior to heating and again after reaching a steady-state mass subsequent to drying.

What is the purpose of moisture content?

Moisture content affects the processibility, shelf-life, usability and quality of a product. Accurate moisture content determination therefore plays a key role in ensuring quality for many industries including Food, Pharmaceuticals and Chemicals.

What is determination of moisture content?

Moisture content is, simply, how much water is in a product. It influences the physical properties of a substance, including weight, density, viscosity, conductivity, and others. It is generally determined by weight loss upon drying.

Is the mechanism of sorption hysteresis in wood?

The mechanism of moisture uptake by wood are different in the hygroscopic and over-hygroscopic moisture ranges and due to methodical issues, most studies of sorption hysteresis have been performed in the hygroscopic range.

Which is bigger hysteresis in earlywood or latewood?

As seen earlier, in earlywood, the swelling hysteresis is bigger in tangential than in radial direction, while the amount of swelling hysteresis is the same in both directions in latewood. We may conclude that hysteresis in swelling may depend on wood porosity, but more data would be needed to verify the trend.

Why does moisture play a role in degradation?

Moisture influences most physical wood properties and plays an important role in degradation processes. Like most other porous materials, wood exhibits sorption hysteresis. That is, the moisture content is higher if equilibrium is reached by desorption than if it is reached by absorption under the same ambient climate conditions.

When is hysteresis no longer present in swelling?

Hysteresis is no longer present when swelling/shrinkage strains are considered versus moisture content, indicating that wood deforms to the same extent whether an amount of moisture is desorbed or adsorbed. Furthermore, swelling anisotropy, in the tangential and radial directions, is found to increase with increasing porosity.