Should you wash rice before cooking? Here’s the science

Rice is a staple food for billions of people in Asia and Africa. It is also a versatile ingredient for many iconic dishes from around the world, including dolmades from Greece, risottos from Italy, paella from Spain and rice pudding from the United Kingdom.

Despite its universal appeal, the question asked in every kitchen, whether it’s a professional kitchen or your own home, is whether you should pre-wash (or rinse) your rice before cooking it.

What do chefs and cooks say?

Culinary experts claim that pre-washing rice reduces the amount of starch extracted from the rice grains. You can see this in the cloudy rinse water, which research has shown is the free starch (amylose) on the surface of the rice grain produced during the milling process.

In culinary circles, washing some dishes is recommended when a separated grain is sought. But for other dishes such as risottos, paella and rice pudding (where you need a sticky, creamy effect), washing is avoided.

Other factors, such as the type of rice, family tradition, local health warnings and even the perceived time and effort required, will influence whether people pre-wash their rice.

Close-up of a golden mushroom risotto with pieces of Parmesan cheese on top
For risotto, traditionally prepared with arborio rice, rinsing the rice is not recommended, to help enhance the creamy texture of the dish. Shutterstock

Is there evidence that washing rice makes it less sticky?

A recent study compared the effect of washing on the stickiness and hardness of three different types of rice from the same supplier. The three types were glutinous rice, medium grain rice and jasmine rice. These different types of rice were either not washed at all, washed three times with water, or washed ten times with water.

Contrary to what chefs will tell you, this study showed that the washing process had no effect on the stickiness (or hardness) of the rice.

Instead, the researchers showed that the stickiness was not due to the surface starch (amylose), but rather to another starch called amylopectin, which is leached from the rice grain during the cooking process. The amount leached differed between rice grain types.

So it is the variety of rice (and not the washing) that is critical to its stickiness. In this study, glutinous rice was the stickiest, while medium-grain rice and jasmine rice were less sticky and also harder, as tested in the laboratory. (The hardness is representative of the textures associated with biting and chewing.)

Close-up of a fried rice dish with chicken, vegetables and a sunny side egg on top
Fried rice dishes, such as nasi goreng, tend to use less sticky rice varieties, leading to a fluffier texture. Shutterstock

You might want to wash your rice after all

Traditionally, rice was washed to rinse away dust, insects, stones and bits of husk left behind when the rice was hulled. This may still be important for some parts of the world where processing is not as rigorous, and may provide peace of mind for others.

More recently, due to the intensive use of plastics in the food supply chain, microplastics have been found in our food, including rice. The washing process has been shown to rinse up to 20% of the plastic from uncooked rice.

The same study found that regardless of the packaging (plastic or paper bags) you buy rice in, it contains the same levels of microplastics. The researchers also showed that plastics in (pre-cooked) instant rice are four times as high as in uncooked rice. If you pre-rinse instant rice, you can reduce the amount of plastic by 40%.

It is also known that rice contains relatively high levels of arsenic, because the crop absorbs more arsenic during growth. Washing rice has been shown to remove about 90% of bioaccessible arsenic, but it also washes away a large amount of other nutrients important to our health, including copper, iron, zinc and vanadium.

For some people, rice provides a small percentage of their daily intake of these nutrients and so will have a small impact on their health. But for populations that consume large amounts of heavily washed rice every day, this could impact their overall diet.

In addition to arsenic, another study also looked at other heavy metals, lead and cadmium; it was found that pre-washing reduced the levels of all these substances from 7 to 20%. The World Health Organization has warned about the risk of exposure to arsenic from water and food.

The arsenic content in rice varies depending on where it is grown, the rice varieties and the way it is cooked. The best advice remains to pre-wash your rice and ensure you consume a variety of grains. The most recent study in 2005 found that the highest arsenic levels were in the United States. However, it is important to keep in mind that arsenic is present in other foods, including products made from rice (cakes, crackers, cookies and cereals), seaweed, seafood and vegetables.

Can washing rice prevent bacteria?

In short, no. Washing rice has no effect on the bacterial content of the cooked rice, as high cooking temperatures kill any bacteria present.

What’s more concerning is how long you store cooked rice or washed rice at room temperature. Cooking rice does not kill the bacterial spores of a so-called pathogen Bacillus cereus.

If wet rice or cooked rice is left at room temperature, the bacterial spores can be activated and begin to grow. These bacteria then produce toxins that cannot be eliminated by cooking or reheating; these toxins can cause serious gastrointestinal illness. So make sure you don’t keep washed or cooked rice at room temperature for too long.The conversation

Evangeline Mantzioris, Nutrition and Nutritional Sciences Program Director, Certified Practicing Dietitian, University of South Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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