13/09/2022

## How do you calculate equilibrium moisture content?

One approach to estimate the EMC is to divide the percent RH by a factor of 5 (McConnell 2016). Thus, for a relative humidity of 75%, the estimated EMC would be 15%.

How do you calculate moisture content of water activity?

Measuring Water Activity Since water activity is the ratio of the water vapor pressure of the sample to the water vapor pressure of pure water under the same conditions, it is also equal to the equilibrium relative humidity, ERH (expressed in %), divided by 100.

What is the relationship between equilibrium relative humidity and water activity?

Water activity is equal to equilibrium relative humidity divided by 100: (a w = ERH/100) where ERH is the equilibrium relative humidity (%). Relative humidity sensors of great variety are available for this purpose, including electric hygrometers, dewpoint cells, psychrometers, and others.

### How do you explain the increase of the equilibrium moisture content with water temperature?

EMC is related to temperature and relative humidity. If the temperature remains constant and the humidity increases, the EMC will increase. So for example, at 70 degrees with a relative humidity of 40%, the EMC is 7.7%. If the temperature remains at 70 degrees and the humidity increases to 77%, the EMC is 14.9%.

What is meant by equilibrium moisture content?

: the condition of balance with the moisture content of the air, being in wood equivalent to about 15 percent of moisture at which level wood neither takes on nor loses moisture when exposed to air.

What is equilibrium moisture content of a material?

The equilibrium moisture content (EMC) of a hygroscopic material surrounded at least partially by air is the moisture content at which the material is neither gaining nor losing moisture. The value of the EMC depends on the material and the relative humidity and temperature of the air with which it is in contact.

#### What is equilibrium moisture content in drying?

What is the relationship between water content and water activity?

The relationship between water content and water activity is complex and related to the relative humidity of the food and its water content. This relationship must be determined for each specific food item. It is easy to assume that foods with higher water content will have a higher water activity than dry foods.

Why is water activity 0.6 important?

Common bacteria do not grow at water activities below 0.9, and no microbial growth occurs below 0.6. In some cases, when a w limit for growth is reached, sporulation occurs. Therefore, water activity is an important parameter related to the control of bacterial growth and determines the shelf life of many foods.

## What is equilibrium relative humidity and how it is related with water activity of a food sample and relative humidity surrounding a food sample?

The equilibrium relative humidity (ERH) of a food product is defined as relative humidity of the air surrounding the food that is in equilibrium with its environment. When the equilibrium is obtained, the ERH (in percent) is equal to the water activity multiplied by 100, i.e. ERH (%) = aw × 100.

What is the significance of the equilibrium moisture content?

The concept of equilibrium moisture content (EMC) is important in the study of drying and storage of fruits, vegetables and grains. The EMC helps to decide the stability of food at particular moisture content in the given environment.

What do you understand by equilibrium moisture content?

### What is the difference between equilibrium moisture content and free moisture content?

In a general drying condition, the water (liquid) which can actually carry out evaporation removal is to the Equilibrium moisture content We. The rate of the water (liquid) which can carry out evaporation removal to the Equilibrium moisture content We is called the Free moisture content Wf.

How does equilibrium moisture content influence drying?

The e.m.c. is important as drying may be carried out unnecessarily resulting in a reduction in the capacity of a given drying system, a higher cost of drying, and an economic loss. The difference in e.m.c. values for a particular product are often due to variations in measuring techniques and grain varieties.

What is significance of equilibrium moisture content?

#### What is the difference between critical moisture content and equilibrium moisture content?

The point which shifts to the Decreasing drying period from the Constant drying period is called the Critical moisture content Wc. The moisture content in which dryness does not advance any more is called the Equilibrium moisture content We.

What is equilibrium moisture content write its significance also?

Does high moisture content mean high water activity?

Generally people think that if the moisture content of a food commodity is reduced obviously the water available for the microorganisms will also be reduced and hence the food commodity will be less prone for the growth of microorganisms. Higher moisture content does not necessarily means high water activity.

## Is moisture content and water content same?

Water content and moisture content are the same, meaning the quantity of water in a material.

Can water activity be greater than 1?

The activity coefficient can be higher than 1. This is not a problem at all. Typically, activity coefficients for polar compounds as water and alcohols (methanol, ethanol, propanol, butanol, etc…) are larger than the unity because the system is strongly non-ideal.