What Is Granularity?

Particle size refers to the size of the particles. Usually, the particle size of sphere particles is expressed by diameter, and the particle size of cube particles is expressed by side length. For irregular particles, the diameter of a sphere that has the same behavior as the particle can be taken as the equivalent diameter of the particle. The size of the particle size is usually expressed by D50, D97, specific surface area and other indicators.

There are several key indicators for representing the granularity characteristics:

The particle size of a food is a characteristic of the food, and it depends on factors such as the type of the food, the method of use, and the required taste. Generally speaking, the smaller the particle size of the food, the more favorable the release of flavor components, and the softer the touch on the oral cavity, the better the effect on taste. Fine foods can beautify the taste. This is especially important for foods with high moisture content such as sauces and pastes, and it is more prominent for chocolate.

The methods commonly used in the laboratory to determine the particle size composition of materials include sieve analysis, sedimentation, laser and microscopy.

The sieve analysis method is used to determine the particle size of 0.038 ~ 250 mm material. The measurement range of the standard laboratory sieve is 0.038 ~ 6 mm. The microscope method can measure the projected area of the particles one by one to determine the particle size. The range of optical microscope measurement is 0.4 ~ 150 m, the particle size of the lower limit of electron microscope can reach 0.001 m or even smaller.

The commonly used particle size analyzers are laser particle size analyzer, ultrasonic particle size analyzer, extinction optical deposition instrument and X-ray deposition instrument.

The particle size test often needs to be repeated because there are deviations between the results of multiple measurements of the same sample. Repeatability index is the most important index to measure the quality of a particle size testing instrument and method. The granularity repeatability calculation can be expressed by the following formula.

=

In the formula:

n-number of measurements (generally n10);

x _i -typical value of each test result (generally D50 value);

x-mean of typical values of multiple test results

-standard deviation

Factors affecting the repeatability of the particle size test are the factors of the instrument and method itself, the factors of sample preparation, and the factors of environment and operation. The particle size test should have good repeatability, which is the basic requirement for the instrument and operators ^[2] .