[Chemistry Class Notes] on Winnowing Pdf for Exam

India continues to be an agricultural economy predominantly because much of our population resides in villages. As a civilization, we have always been in touch with the earth and its abundance. With the invention of modern-day machines, farmer-friendly technology has made its way into the agricultural space. 

If you have had the privilege of listening to these stories from your parents or grandparents or even better, visiting your native village – have you seen the women of the family sit out on the porch with grains of rice filled in a basket-like structure? They keep throwing the husk aside so that they are left with rice grains alone. This is an example of how winnowing used to be performed in our own kitchens!

What is Winnowing? 

Winnowing refers to the separation of quality rice grains from husk or chaff through the blowing of strong winds. It is crucial in the process of paddy cultivation. In older times, this used to be a tedious process as farmers would have to wait for hours for winds to blow to separate their rice grains from chaff after making these dried grains fall from a height using shovels or sieves. 

Soon enough, the winnowing machine was introduced as industrialization spread globally. Husk is lighter than rice grains, hence it easily gets separated due to the force of the wind. The wind winnowing machine was first invented in Scotland by Andrew Rodger as early as 1737 when he wanted to separate corn. 

Today’s wind winnowing machines have a fan that is rotated through pedaling. The velocity of the wind produced can be controlled through this process of pedaling. Farmers no longer have to wait for the natural winds to blow. They can winnow hundreds of kilograms of rice or paddy in a short span of time. Since they are machines, they can be operated inside a large closed space too which means farmers can benefit even during the rainy season.

Separating grains from the chaff is called winnowing. It is an agricultural technique being used since ancient times. Now a days many machines are available for winnowing.

Winnowing means is the separation of grains from straw by the use of the current of air. The word winnow is originated from the old English word ‘windwian’ which means separation of the mixture through the wind. 

Principle of Winnowing

Winnowing is based on the fact that if a mixture is containing two components and one is lighter than another one, then both the components can be separated by a blow of air. The mixture is allowed to fall from a height. The lighter component gets separated from the heavier component due to wind.

In the above image, it is shown that as empty seeds and debris are lighter than filled seeds, so they get separated by the current of air. 

Wind winnowing machines- It is said that the first winnowing machine was developed by Andrew Rodger in 1737, in Scotland. He was a farmer and developed that machine for separating corn. He named the machine ‘fanner’. Then during the industrial revolution, many types of winnowing machines were developed.

Ancient winnowing machine developed in China 

Modern Winnowing Machine 

Now a days, a single machine is available for winnowing and threshing. Threshing is a process of separating stalks from grain. Farmers used to beat the grains manually to separate their edible part from non-edible parts. Now a days, machines are available for threshing also. Even now a days farmers use only one machine for threshing and winnowing. It makes their work easy and they can complete two tasks at a time. This saves their time and energy. 

Single machine for winnowing and threshing 

Example of Winnowing 

1. Wheat is separated from husk by using winnowing method. Wheat and husk mixture is allowed to fall from a height. Husk being lighter than wheat grains get separated from wheat because of wind or air blow. 

2. Dirt particles can be removed from grains by winnowing. 

3. Corns are separated from straw by winnowing.

Advantages of Winnowing

1. Winnowing is very useful in agriculture. 

2. We get grains and husk separate by winnowing, so husk can be used as food for animals.

3. We can separate grains such as wheat, corn, millet etc. from lighter impurities such as husk, straw, stones etc. by using winnowing. 

Disadvantages of Winnowing

1. This process of separating the components of a mixture does not work for heavier particles such as stones. 

2. Since in winnowing the components of a mixture are separated with the help of wind, it is practically not possible to separate the components that are heavier than grains. Therefore, this process of separation of mixtures has a limited scope.

3. Also, winnowing machines are more efficient than manual winnowing.

Difference Between Winnowing and Threshing 

Conclusion

The study notes on Winnowing provide a complete overview of the process of winnowing, including an overview of its origin, description, and the advances made in the process with the progress of industrialization.