Why Leftover Rice is Risky for Health? Here's the Explanation

JAKARTA - Food waste is often considered a practical solution to save time, money, and groceries. There is nothing wrong with storing and reusing food as long as it is safe.

Using leftovers is a wise habit rather than throwing them away. However, it is important to understand that not all leftover food has the same level of safety. Some of them can actually be dangerous for health if not handled properly.

One of the most risky leftover foods is rice. Even rice that has been reheated can still be a threat to health.

Rice contains a lot of starch and is able to retain moisture, making it an ideal place for the growth of bacteria, especially Bacillus cereus. This bacterium is known as a cause of food poisoning and has a high survival ability because it can form spores that are resistant to heat.

Food waste, including rice, enters the danger zone at temperatures between 5 to 57 degrees Celsius. This temperature range is the ideal condition for bacteria to multiply quickly, above the refrigerator temperature but below the cooking temperature.

Reheating food can generally kill bacteria. However, this is not entirely true for Bacillus cereus. This bacterium is heat resistant, so it can still survive even if the rice has been reheated.

"If the rice is in a dangerous temperature zone, the number of bacteria can double in just 15 to 20 minutes. After an hour, the number can be 8 times because it continues to double," said Clark Casarella, scientist, chef, and food writer from Sioux Falls, South Dakota, quoted from the All Recipes page on Wednesday, April 4, 2026.

The high starch content and low protein in rice make it the perfect environment for bacterial growth. When rice is left in warm and humid conditions, bacteria will develop very quickly.

This phenomenon not only applies to rice, but also to other starchy foods such as couscous, farro, potatoes, and pasta.

"Basically, a warm, moist, and starchy environment is a breeding ground for bacteria that cause food poisoning. Rice is just wet starch. If left alone, the growth of bacteria will be very fast," said Casarella.

Tips for Safely Consuming Leftover Rice

In order to stay safe when eating leftover rice, here are some steps you can take:

The more rice that is cooked and stored, the more likely bacteria will develop.

"The higher the concentration, the more dangerous. Cook only as much as needed," said Casarella.

Don't let the rice sit at room temperature for too long. It's best to cool it immediately after cooking. You can flatten it in a shallow container so that the heat is quickly lost, or even put it in the freezer to speed up the cooling process.

If it is not immediately put in the refrigerator, use the "keep warm" feature on the rice cooker to keep the rice out of the danger zone.

Avoid reheating rice repeatedly. Take only the portion that will be consumed.