Parboiling

FOOD SCIENCE AND PROCESSING 3 (2+1)

Lesson 8 : Rice

Rice starch

Parboiling is particularly good in the case of coarse and medium rice of soft structure because such rices suffer excessive breakage when milled raw. Parboiling involves soaking paddy in water for a short time followed by heating once or twice in steam and drying before milling.

1. Conventional process: This consists of the following steps:
   
   
2. Hot soaking process: The hot soaking process, developed at the Central Food Technological Research Institute, Mysore consists of the following steps:

• Advantages of parboiling:
• Dehusking of parboiled rice is easy.
• Grain becomes tougher resulting in reduced losses during milling. By this , parboiling eliminates breakage completely.
• Milled parboiled rice has greater resistance to insects and fungus.
• Loss of nutrients due to the removal of husk and bran in milling are decreased. During harvesting the vitamin and mineral present in hull ( outer covering of the paddy) and bran coat are dissolved and seeped into the endosperm. Part of the scutellum and germ which are rich in B vitamins get fixed to the grain and hence losses of B vitamins are less.
• Losses of water soluble nutrients due to washing of rice are less in parboiled rice compared to raw rice.
• Parboiling improves digestibility and protein efficiency ratio is higher compaired to raw rice.
• Parboiled rice will not turn into glutenous mass when cooked
• Parboiled rice swells more when cooked to the desired softness.
• Parboiling stabilises the oil content of the bran. The discrete oil globules in the aleurone layer of the native rice grain are ruptured into a band by parboiling.


• Disadvantages of parboiling:
• Sometimes it has an unpleasant smell and change in colour and hence not preferred. Modern methods of parboiling have eliminated this problem. By controlling soaking and steaming, colour and cooking quality can be maintained.