Excellent question. The answer depends on the type of cooker employed. Some don't have a keep-warm feature so as soon as the temperature falls below 140F the 2-hour clock begins ticking. Those that have a keep-warm setting should maintain the temperature at or above 150F so, in theory, you should be able to leave it in the cooker overnight if you wanted. Remember I'm not a microbiologist but, personally, I wouldn't worry until the temperature dropped below 90F where spore germination begins. The bacteria will grow at temperatures as low as 39F (colder than most refrigerators) hence the importance of minimizing storage time.
I didn't mean to imply you should toss it. As long as leftover rice is handled properly, it's perfectly safe for a few days. (Refrigeration slows but does not prevent bacterial growth.)
After a few hours in the danger zone the bacteria germinate and this particular bug produces a heat-resistant toxin similar to C. botulinum but this one likes starches. Back in the 70's, before our current knowledge of the bacterium evolved, Chinese restaurants commonly left unused rice unrefrigerated overnight before turning it into fried rice the next day. Trouble ensued. The USDA figured it out and put an end to the practice.
The Japanese have another defense in addition to refrigeration -- the vinegar in sushi.
I trust ChefOno's comments, but all my Japanese friends save their leftover rice for the next meal (in fridge), It is reheated as a stir-fry or added to a soup base of Okayuu. First I've heard of it being so dangerous....
Rice presents a more serious danger than most other foods. Along with other grains, it likely harbors spores of bacillus cereus, a relatively unknown bacterium that can survive the cooking process. As the poster above mentioned, rice is a perfect breeding ground for bacteria which is usually bad enough, B. cereus can be deadly.
Rice provides a rich moist environment for bacteria to grow. I would either use it immediately after cooking or cook and chill immediately (with minimum exposure to time at room temperature) for future use. If it is leftovers from a meal, I would toss it or compost it.
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Excellent question. The answer depends on the type of cooker employed. Some don't have a keep-warm feature so as soon as the temperature falls below 140F the 2-hour clock begins ticking. Those that have a keep-warm setting should maintain the temperature at or above 150F so, in theory, you should be able to leave it in the cooker overnight if you wanted. Remember I'm not a microbiologist but, personally, I wouldn't worry until the temperature dropped below 90F where spore germination begins. The bacteria will grow at temperatures as low as 39F (colder than most refrigerators) hence the importance of minimizing storage time.
I didn't mean to imply you should toss it. As long as leftover rice is handled properly, it's perfectly safe for a few days. (Refrigeration slows but does not prevent bacterial growth.)
After a few hours in the danger zone the bacteria germinate and this particular bug produces a heat-resistant toxin similar to C. botulinum but this one likes starches. Back in the 70's, before our current knowledge of the bacterium evolved, Chinese restaurants commonly left unused rice unrefrigerated overnight before turning it into fried rice the next day. Trouble ensued. The USDA figured it out and put an end to the practice.
The Japanese have another defense in addition to refrigeration -- the vinegar in sushi.
Rice presents a more serious danger than most other foods. Along with other grains, it likely harbors spores of bacillus cereus, a relatively unknown bacterium that can survive the cooking process. As the poster above mentioned, rice is a perfect breeding ground for bacteria which is usually bad enough, B. cereus can be deadly.
The general rule for leftovers is 4 days. Foods should be refrigerated within 2 hours -- particularly rice as it is potentially dangerous.