Sunday, 21 December 2014

Rice Milling

Milling is a crucial step in post-production of rice. The basic objective of a rice milling system is to remove the husk and the bran layers, and produce an edible,white rice kernel that is sufficiently milled and free of impurities.
Depending on the requirements of the customer, the rice should have a minimum number of broken kernels.

Technology

  • Use rubber roll technology for husking
    Rubber roll huskers produce the best quality. Engleberg-type or "steel" hullers are no longer acceptable in the commercial rice milling sector, as they lead to low milling recovery and high grain breakage.
  • Use a paddy separator
    Separate all paddy from the brown rice before whitening. Paddy separation after husking will lead to better quality milled rice, and reduce overall wear and tear on the rice mill.
  • Consider two-stage whitening
    Having at least two stages in the whitening process (and a separate polisher) will reduce overheating of the grain and will allow the operator to set individual machine settings for each step. This will ensure higher milling and head rice recovery.
  • Grade the milled rice
    Installl a screen sifter to remove small brokens and chips from the polished rice. Rice with a large number of small brokens (or brewer’s rice) has a lower market value. The small brokens can be utilized to produce rice flour.

    Management

    • Monitor and replace spare parts regularly
      Turning or replacing rubber rolls, refacing stones, and replacing worn screens regularly will keep milled rice quality high at all times.

    Milling system

    A rice milling system can be a simple one or two step process, or a multi stage process.
    • In a one step milling process, husk and bran removal are done in one pass and milled or white rice is produced directly out of paddy.
    • In a two step process, removing husk and removing bran are done separately, and brown rice is produced as an intermediate product.
    • In multistage milling, rice will undergo a number of different processing steps. Depending on whether the the paddy is milled in the village for local consumption or for the marketing rice milling systems can be classified into the categories village rice mills and commercial mills.
    Village milling
    Hand pounding of paddy in a mortar with a pestle is the traditional milling process in remote villages. This type of milling can be found in rural communities and are used for service milling paddy of farmers for home consumption. 

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