Cleaning Food



Threshing is the process of loosening the edible part of grain (or other crop) from the husks and straw to which it is attached. It is the step in grain preparation after reaping and before winnowing, which separates the grain from the chaff. Threshing does not remove the bran from the grain.

Threshing may be done by beating the grain using a flail on a threshing floor. Another traditional method of threshing is to make donkeys or oxen walk in circles on the grain on a hard surface. A modern version of this in some areas is to spread the grain on the surface of a country road so the grain may be threshed by the wheels of passing vehicles.


Wind winnowing is an agricultural method developed by ancient cultures for separating grain from chaff. It is also used to remove weevils or other pests from stored grain. Threshing, the loosening of grain or seeds from the husks and straw is the step in the chaff-removal process that comes before winnowing.

In its simplest form it involves throwing the mixture into the air so that the wind blows away the lighter chaff, while the heavier grains fall back down for recovery. Techniques included using a winnowing fan (a shaped basket shaken to raise the chaff) or using a tool (a winnowing fork or shovel) on a pile of harvested grain.


In our daily lives we come across so many situations in which we have to separate some substances from a mixture in order to get a suitable substance for use. Some of the substances are easily separable just by taking out the impurities with hand. This method of separation is known as handpicking. But some of them cannot be removed by hand and we need some other methods of separation for such mixtures.

The method in which substances in a mixture can be separated by just picking them out with the help of hand from the mixture is known as handpicking method. It is one of the various methods which are carried out in dry conditions. The substances which are separated with the help of this method can be useful product or the impurities which need to be removed or both the substances which are separated can be useful products. This method is useful only when the substance which needs to be separated is in small quantity.

The substances in the handpicking method can be separated on the basis of size, color, shape, weight etc. Handpicking examples are: If in a bowl, there are 7 round shaped boxes and 3 rectangular boxes then the boxes can be easily separated on the basis of shape. For example: In our house, our mother separates stones and insects from rice simply by hand.


Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration, or electromagnetism. In geology, sedimentation is often used as the opposite of erosion, i.e., the terminal end of sediment transport. Settling is the falling of suspended particles through the liquid, whereas sedimentation is the termination of the settling process. In estuarine environments, settling can be influenced by the presence or absence of vegetation. Trees such as mangroves are crucial to the attenuation of waves or currents, promoting the settlement of suspended particles.

Sedimentation may pertain to objects of various sizes, ranging from large rocks in flowing water to suspensions of dust and pollen particles to cellular suspensions to solutions of single molecules such as proteins and peptides. Even small molecules supply a sufficiently strong force to produce significant sedimentation.


Filtration is any of various mechanical, physical or biological operations that separate solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass. The fluid that passes through is called the filtrate.[1] In physical filters oversize solids in the fluid are retained and in biological filters particulates are trapped and ingested and metabolites are retained and removed. However, the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size, filter thickness and biological activity). Filtration occurs both in nature and in engineered systems; there are biological, geological, and industrial forms. For example, in animals (including humans), renal filtration removes wastes from the blood, and in water treatment and sewage treatment, undesirable constituents are removed by absorption into a biological film grown on or in the filter medium, as in slow sand filtration.