Post harvest Technologies

Threshing

  1. Threshing is the process of beating paddy plants in order to separate the seeds or grains from the straw.
  2. To maintain the high quality of the harvested grains, it should be threshed immediately after harvesting.
  3. Avoid field drying and stacking for several days as it affects grain quality due to over drying. Stacked grains of high moisture content results in discoloration or yellowing.

Drying

  1. Drying is the process of removal of excess moisture from the grains.
  2. Once dried, the rice grain, now called rough rice, is ready for processing.
  3. Proper drying results in increased storage life of the grains, prevention of deterioration in quality, reduction of biological respiration that leads to quality loss of grains, and optimum milling recovery.

Parboiling

  1. Parboiling is a premilling hydrothermal treatment given to unhulled rice (rough rice) to improve its milling quality, nutritive value, cooking quality and storability.
  2. The process is accomplished in three steps: soaking, steaming and drying.
  3. Traditionally, parboiling was done either by single or double boiling method.
  4. Single boiling method involves soaking the unhulled rice in water at room temperature followed by open steaming for 20-30 minutes using iron kettles and then sun drying.
  5. In double streaming method, the unhusked rice is first steamed to raise its temperature and then soaked in cold water for 24-36 hrs. After soaking, it is steamed second time for 20-30 minutes followed by sun drying.

    Milling

    1. Milling is the process wherein the rice grain is transformed into a form suitable for human consumption, therefore, has to be done with utmost care to prevent breakage of the kernel and improve the recovery.
    2. Brown rice is milled further to create more visually appealing white rice.
    3. After harvesting and drying, the paddy is subjected to the primary milling operation which includes de-husking as well as the removal of bran layers (polishing) before it is consumed. In this process the rice which is obtained after milling is called raw rice.
    4. Another process through which rice is obtained after milling is called "Parboiling Rice." Nearly 60% of the total rice produced in India is subjected to parboiling.
    5. Rice milling losses may be qualitative or quantitative in nature. Quantitative or physical losses are manifested by low milling recovery while low head rice recovery or high percentage of broken kernel reflects the qualitative loss in rice grains.
    Storage
         Storage is the process of keeping grains, whether in bags or in bulk, in a storage structure designed to protect the stored product from inclement weather and pests for a short or long period of time to await processing or movement to other location.