Why Your White Rice Turned Yellow And How To Prevent It Next Time

The fluffy grains of freshly-cooked rice are delicious, but it's what comes in the following days that's even better. The day-old grains can be turned into everything from fried rice to a hearty casserole. However, coming across white rice that's already turned yellow may throw a wrench in those plans. Although you may encounter yellow rice in the grocery store, having the right kernels change color on you is a completely different thing. Intentional yellow rice is actually white rice that takes on its hue from the brightly-colored spices added during cooking, such as turmeric, saffron, or annatto. 

Some white rice is meant to look a little off-white, too. Pre-cooked kernels, like parboiled rice, come with a naturally cream or pale yellow complexion due to the pigmented outer husk moving to the center of the grain. Other types of rice, like basmati, are specifically aged, resulting in a slightly golden color. In these cases, rice that's slightly yellow isn't a cause for concern. However, if your previously white grains suddenly discolor, anything from the way it was cooked to the utensils used to stir it could be the culprit.

Typically, food taking on another hue is a sign of growing mold or a quality breakdown that means it's unsafe to eat. However, yellowing in rice doesn't come from just one source — although it does often stem from how you store it. Heat is a major cause of rice yellowing after it's been cooked. The change in color is like a delayed Maillard reaction; when the grains are still hot and compact together in a container in the fridge, the temperature results in a chemical change that changes the rice's color. 

If mold, slime, or a sour odor accompany the yellowing, the rice should be tossed. Even before the rice is cooked, you may notice some grains start to change appearance. Heat can increase uncooked rice's flavonoids, which are antioxidant-rich compounds that give plants and food their color. The processing of white rice significantly decreases its nutrients, but prolonged heat exposure will concentrate the flavonoids in the grains, leading to a yellowed look.

Japonica rice, the short to medium grain variety, has more flavonoids than long-grain indica rice, so the smaller rice granules may be more prone to discoloration. However, it will take a few months for any white rice to change color, so keeping a small supply that you eat regularly should prevent that. An antioxidant boost is hardly the worst thing for food, but heat exposure also leads to a deterioration in quality, so toss the uncooked rice if it does change shades.

Along with heat, air exposure often leads to food discoloration. Oxidation, a process in which oxygen exposure degrades the chemical structure of food, results in a color change and other alterations to the rice. Chemical change aside, air exposure in general makes rice susceptible to bacteria growth, resulting in a color, texture, and taste breakdown. If the rice experiences discoloration after oxygen exposure, take it as the first sign it needs to be tossed.

Excess moisture in both cooked and uncooked rice can also lead to yellowing. The moisture diminishes the quality of the grains, and eventually results in mold that may appear yellow. When storing uncooked rice, keep it in a cool, dark place to preserve its lifespan. For the steamed grains, follow the overnight step you shouldn't skip when making fried rice.

Spreading your rice grains out on a baking sheet while they're still hot allows any lingering moisture from the pot or rice cooker to dissipate. Place the baking sheet in the fridge as the rice cools, then immediately transfer the grains to an airtight container when they're cold enough. The lack of moisture and air should extend its lifespan, but remember that you can store cooked rice in the fridge for just four to six days.

If you check on simmering rice and discover that it's taken on a yellow hue, this doesn't mean turmeric or saffron somehow found their way into the grains. The change in color may stem from your tap. Hard water is notorious for turning fabrics from bright white to a pale yellow, and it could do the same to rice. The excess of magnesium and calcium in the water, as well as a build up of tannins, result in mineral deposits that give off a yellowed hue.

Since the outer layers of the grains are removed during the polishing process, white rice absorbs liquid fairly quickly, taking in all the minerals that hard water possesses. While this does make the ingredient cook quickly, hard water takes a while to reach boiling point, giving the rice ample time to change color from the mineral-rich water. Varieties like basmati rice may be more vulnerable to yellowing, since soaking them in water is recommended for a fluffier texture.

While it will change the look of rice, hard water doesn't necessarily make food unsafe to eat. However, it will alter the grains' nutritional value, and could have a negative impact on their taste and texture. The rice may still be slightly hard or chewy after cooking, and the water's bitter, mineral taste will seep into the rice. If hard water is a problem for you, it may be worth using distilled water to cook.

Any pot that's deep enough to contain a few cups of rice and water may seem like the best choice for cooking, but the material of your cookware is another important factor to consider. Reactive cookware is known to have an impact on food, altering components like its taste and color. Materials like aluminum, copper, and iron can release miniscule amounts of metal into food, leading to discoloration. Even the spoon you stir the grains with matters, as reactive metal utensils could be altering how your food tastes and looks. However, what you add to the rice determines whether the metal will yellow it. 

Reactive cookware releases metals when met with acidic ingredients. That splash of rice vinegar when making sushi rice or squeeze of lemon juice to brighten the grains' flavor could alter the taste and color of your rice. You should also avoid making risotto recipes in reactive cookware, since the acidic white wine will impact the grains. Rice turning yellow after being cooked in reactive cookware, as well as taking on a bitter or metallic taste, could indicate the presence of metal in the grains. 

In small amounts, this isn't harmful, but it's definitely not something you should be consuming everyday. Instead, use non-reactive cookware like stainless steel, ceramic, or enamel-coated metals to steam your rice. While the pots themselves may experience discoloration, like the slight rainbow wash on stainless steel, this won't have any impact on your rice.

Heating things for far too long or at an extreme heat can definitely cause discoloration, but it's not as simple as burning when it comes to rice. As the grains cook, the starches swell with water and break down, thickening the water and allowing the grains to stick together. This process, called gelatinization, is what makes rice ready to eat. When gelatinization occurs, the grains should look slightly translucent. 

If the rice cooks past that point, though, the starches may undergo dextrinization, which results in yellowed rice. As the starches are further exposed to more heat and the water dissipates, they turn into the carbohydrate known as dextrin. This carb starts out white, but can take on a brown or yellow hue as time goes on. Cooking the rice on high makes yellow dextrin more likely, as does the presence of an acidic ingredient, like lemon juice or rice vinegar. 

Make sure to use 1.5 cups of water for every cup of rice, and check the grains regularly to make sure they have enough moisture. Not rinsing rice before cooking could make the yellowed color more apparent, since all the excess starch that remains will produce even more dextrin. Toasting the rice beforehand may also yellow it due to the lack of water, but this isn't always bad. Unless the grains burn, toasting them is a great method to add more flavor to white rice since they'll take on a deeper taste.