Posts tagged: Digestibility

What are the Effects of Cooking Rice in a Pressure Cooker

By , September 1, 2012

It’s well known that cooking rice in a pressure cooker reduces cooking time by half.  What about the cooking result? Users told us that rice cooked in Instant Pot is softer, stickier and tasted better.  We want to find out what scientists say about this.  It turns out that there are quite a few scientific research projects on this subject.  The effects of pressure cooking rice, grains and legumes can be summarized on 3 aspects.

1. Texture Change

Cooking under pressure or at higher temperature starch in rice gelatinizes to the maximum degree. This is why pressure cooked rice has a softer and stickier grain texture in comparison to boiled and steamed rice at normal pressure. Under electronic microscope, a grain of rice appears to have more pores when cooked under pressure. Please see the images between magnified 500 and 5000 times. These pores make the rice looks a bit off-white (greyish). Furthermore, tough fibers in brown rice and bran are significantly softer which give the food a better tasting texture.

Rice grain cooked under pressure. Magnified 500 times

Rice grain cooked under pressure. Magnified 500 times

Rice grain cooked at normal pressure. Magnified 500 times

Rice grain cooked at normal pressure. Magnified 500 times

Rice grain cooked under pressure. Magnified 5000 times

Rice grain cooked under pressure. Magnified 5000 times

Rice grain cooked at normal temperature. Magnified 5000 times

Rice grain cooked at normal temperature. Magnified 5000 times

2. Improving Digestibility and Increasing Nutritional Value

Starch gelatinization, a change of structure into a form that resembles gelatin, improves digestibility. Pressure cooking rice, grains and beans produces positive nutritional gain, from the increased digestibility of the macronutrients (protein, fiber and starch) and the increased bioavailability of the essential minerals.

Aflatoxin-producing members of Aspergillus are common and widespread in nature.

Aflatoxin-producing members of Aspergillus are common and widespread in nature.

3. Eliminating Harmful Fungi and Bacteria

Rice, if not stored properly, may carry fungal poisons called aflatoxins, a potent trigger of liver cancer. A survey found that 6% of uncooked rice collected from markets in Seoul contained aflatoxins.  Conventional boiling and steaming rice at under 100°C (212°F) is not sufficient to kill all aflatoxins. Study had shown that pressure cooking at higher than 100°C (212°F) was capable of reducing aflatoxin concentrations to safe levels.

 

Use your pressure cooker for rice cooking.  This will make your rice taste better, more digestible and nutritious, and most importantly carcinogenic aflatoxin free.

 

References

  • Kataria A, Chauhan BM.: “Contents and digestibility of carbohydrates of mung beans (Vigna radiata L.) as affected by domestic processing and cooking”. Plant Foods Human Nutrition . 1988;38(1):51-9.
  • Leelayuthsoontorn P, Thipayarat A.  “Textural and morphological changes of Jasmine rice under various elevated cooking conditions”.  Food Chemistry, 2006, 96(4): 606-613
  • Rashmi S, Urooj A. “Effect of processing on nutritionally important starch fractions in rice varieties”.  International Journal of Food Sciences and Nutrition. Jan. 2003, 54(1):27-36.
  • Sagum, R., Jayashree Arcot. “Effect of domestic processing methods on the starch, non-starch polysaccharides and in vitro starch and protein digestibility of three varieties of rice with varying levels of amylose.” Food Chemistry 2000 Vol. 70 No. 1 pp. 107-111
  • Eating Well: ”What is the Effect of Pressure Cooking on Nutrition?”
  • Science News: “Putting the Pressure on Poisons”