The advantage of rice cookers is their set-it-and-forget-it feature, allowing you to walk away while the rice cooks. Unfortunately, forgetting about the rice inside for hours on end is a common issue that many face, making them wonder how long you can leave rice in the cooker until it becomes unsafe to eat.
In an unplugged rice cooker at room temperature, your rice becomes unsafe just after 2 hours, but using the keep warm feature present on most rice cookers allows you to extend this window. With the warm function on, the rice is safe to eat for up to 12 hours, in so long as it stays above 60° Celsius (140° Fahrenheit), as this discourages the growth of the bacteria Bacillus cereus.
This bacteria can survive regular cooking temperatures, so if your rice is left off the heat, spores can germinate and produce toxins that can make you ill.
How Do You Keep Rice From Spoiling in a Rice Cooker?
The main reason rice spoils is that it contains microscopic spores that proliferate into bacteria at room temperature. To prevent this, rice cookers hold temperatures well above that which the bacteria can grow in, both while cooking and on the keep warm setting.
If your rice cooker falls below this temperature, your rice will begin to spoil, and quickly at that. In addition to this, if rice spoiled inside your cooker even once before, bacteria can remain on the surface and spread into any rice cooked inside of it afterward.
Make sure that your cooker has, and switches to, its “keep warm” setting after it finishes cooking and that the keep warm setting remains at a temperature above 60° Celsius (140° Fahrenheit).
Properly cleaning, and caring for your cooker, ensuring it is cleaned thoroughly and isn’t scratched or dented will deter bacteria from clinging to the surface, further helping to preserve any future batches.
Why Does Rice Spoil Easily in a Rice Cooker?
If you are experiencing consistent rice spoilage every time you make a new batch, see if any of the following issues are happening.
- If your rice cooker is not defaulting to the warm setting after the rice has finished cooking, this could be the cause of your rice spoiling while still in the rice cooker.
- If the non-stick surface of your rice cooker is damaged, this can allow bacteria to grow on the surface and spoil your rice. This is near impossible to combat and it tends to be easier to purchase a new rice cooker at this point.
- Your rice cooker isn’t keeping the rice out of the temperature danger zone [1] and is allowing the wet environment to breed bacteria that spoils your rice.
- If you have an aluminum insert in your rice cooker that is non-anodized, then your rice may be coming into contact with bare aluminum which causes a chemical reaction to occur. This chemical reaction will cause your rice to spoil.
- If you have had a previous incident of rice spoiling, bacterial spores may be lodged on certain parts of your rice cooker like the gaskets or vents, causing every batch afterward to spoil. To fix this, either buy a new rice cooker or disassemble your rice cooker and bleach it in 1 part bleach, 9 parts water. Wash thoroughly afterward and rinse with cold water.
- Human error; if you lift up the lid too much, cold air can seep in and create a mismatch in the temperature environment, causing the temperature danger zone to occur.
Can I Leave My Rice Cooker on Warm Overnight?
While a lot of rice cooker manufacturers do not recommend it, you can technically leave it overnight on warm, in so long as the keep warm function maintains the rice at a temperature above 75° Celsius or 145-165° Fahrenheit.
If it is below this temperature, the rice is likely to grow bacteria on it. Another issue with leaving the rice cooker on warm overnight is you risk drying your rice out or even burning it.
When it comes to me, myself and I, there’s rarely an occasion where I choose to keep the rice cooker on warm overnight. There’s no way for me to monitor the appliance when I’m asleep and even though the device is safe and automated, it’s still an electrical device that’s being heated. If something was to malfunction, the consequences could be dire.
How To Tell If My Rice Has Gone Bad?
Look out for the following signs that your rice is off or has gone completely bad.
- The smell of your rice is off/strange. If your rice has an unpleasant, sour smell to it, it is a sign that there might already be bacteria growing on it. It is best to chuck it.
- The rice has become slimy. This means that there was too much moisture in the rice when it was stored. Too much moisture promotes bacterial growth and can lead to the first stage of fermentation.
- The rice is extremely tough, dry, or crumbly. This means that the rice has been left in storage for too long and has lost all of its moisture content. Even if it doesn’t smell strange yet, you may not want to reheat and consume.
If you reheat rice that has gone bad, you may experience food poisoning which comes with diarrhea, vomiting, and an upset stomach as its symptoms. Drinking plenty of water is important if you have food poisoning so that you do not become dehydrated.
If you want to eat during this time period, eat soothing foods or plain foods like bananas and crackers.
Is It Safe to Reheat Your Leftover Rice?
While some people believe that reheating rice is an unsafe practice, if you store the rice properly, handle it with care, and use the right cooking methods to reheat it, then it is safe to reheat it. Why do some people believe it is unsafe?
Unfortunately, the dormant bacteria Bacillus cereus can survive some cooking processes, leading to food poisoning if the rice isn’t cooked or stored properly. To help you avoid this, make sure to follow these tips.
- When reheating your rice, make sure it reaches a high temperature above the danger zone of 4.4-60°Celsius or 40-140° Fahrenheit. Ideally, you want to heat it at or above 165° Fahrenheit.
- If planning on storing cooked rice to reheat later on, cool it down quickly by dividing the rice up into shallow containers and then placing it directly into the fridge or freezer. The recommendation here is to cool the rice within 2 hours down to 70° Fahrenheit and to just below 40° Fahrenheit within 4 hours. When storing the rice, ensure it is below 4.4°Celsius or 40° Fahrenheit. This prevents bacteria from growing.
Can You Reheat Rice in a Rice Cooker?
If you are planning on reheating leftover rice, you can safely do it in a rice cooker in so long as the rice cooker can heat it up to 75° Celsius or 165° Fahrenheit [2]. If your rice cooker does not accommodate this high of a temperature setting, then reheating it in the rice cooker is not a safe option.
To figure out if your rice cooker has a reheat option, look for it on the interface and double-check the manual to see the temperature associated with this mode. If your rice cooker does reheat up to 165° Fahrenheit then proceed with the following instructions for reheating.
- Add in a tablespoon or so of cold water into the rice cooker and add in your rice. Adding in the water will give the rice just enough moisture to keep it from drying out but not too much to prevent it from getting soggy.
- Press the reheat option. Leave it to reheat for at least an hour. Check it thoroughly when removing from the rice cooker to ensure that it has been heated all the way through.
Please note: some rice cookers may have delay timers on them which may prompt people to place previously cooked rice into the rice cooker and leave until the timer begins.
This is not recommended as leaving cooked rice at room temperature (prior to reheating it) can cause bacteria to grow. Not only can the bacteria then infect your rice cooker, but if something goes wrong with the reheating process, it can make you ill as well. This means that it is best to reheat your rice right out of the refrigerator.
How Long Can Rice Be Kept in a Refrigerator Before it Becomes Unsafe?
Permitting that your cooked rice was cooled down quickly and placed into the refrigerator immediately after cooking, it can be kept in the fridge for up to 4 days in a sealed container.
This means that you can also reheat it up to 4 days after cooking, but the sooner you reheat it the safer it will be. If you are freezing your rice, it will last between 6-8-months but should be reheated immediately after removing from the freezer and consumed.
Can You Consume Cold Rice & Not Reheat It?
Yes, you can. As long as it is refrigerated at the right temperature (under 5°C or 41°F) and you do not allow it to get to room temperature.