<figure id="attachment_436428" aria-describedby="caption-attachment-436428" style="width: 3360px" class="wp-caption alignnone"><a href="#" data-ident_hash="330a86ee"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2025/08/3076c48ca29087971ea20f452febcfa4.jpg" alt=""></a><figcaption id="caption-attachment-436428" class="wp-caption-text">It is impossible to identify food contaminated with Bacillus cereus by smell or appearance alone. &#8230;&#8230;</figcaption></figure>
<h3><span class="strongInContent"> What is &#8220;Bacillus cereus&#8221; that increases explosively when left at room temperature x long time&#8230;?</span></h3>
<p> You may sometimes leave uneaten fried rice, pilaf, spaghetti, or other stir-fry dishes and eat them later. However, eating them after leaving them at room temperature for a long time may cause food poisoning such as diarrhea and vomiting.</p>
<p> Some people may think it is safe to heat the food again before eating it, but this is troublesome because the Bacillus cereus that causes this food poisoning is heat-resistant and is not killed even by heating. This type of food poisoning is known as &#8220;fried rice syndrome.</p>
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<p> Shintaro Toda of the Machida Institute of Prevention and Sanitation (Machida City, Tokyo), who is in charge of the management department of the institute, speaks of food poisoning caused by Bacillus cereus as follows.</p>
<p><span class="strongInContent"> It can also occur at caterers and box lunch shops,&#8221; said Shintaro Toda of the Machida Preventive Health Research Institute (Machida City, Tokyo). The risk of Bacillus cereus growth increases if the food is cooked the day before or prepared in large quantities and left at room temperature until it cools down.</span></p>
<p> Bacillus cereus is a soil bacterium that is widely found in the natural environment in soil, water, and dust, and is also found on agricultural, livestock, and marine products such as rice and wheat. Moreover, this bacterium is resistant to heat and is not killed by the temperature at which rice is cooked or spaghetti is boiled.</p>
<p> According to the &#8220;Food Sanitation Window&#8221; website of the Tokyo Metropolitan Bureau of Public Health, the optimal temperature for Bacillus cereus to multiply most actively is 28 to 35°C. If cooked fried rice or spaghetti is left at room temperature for a long time after it has cooled, the bacteria will multiply in large numbers.</p>
<p> Bacillus cereus can be found on crops in the field,&#8221; said Shohei Matsumoto, director of the Institute of Food Environment and Hygiene (Maebashi City, Gunma Prefecture). It can also be on the surface of vegetables, but it does not cause food poisoning immediately after eating them.</p>
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<h3><span class="strongInContent">In summer, &#8220;Eat up cooked food immediately! is the principle.</span></h3>
<p> This Bacillus cereus is a spore-forming bacterium that forms structures called spores, which are resistant to heat and can survive even under adverse conditions. According to &#8220;Food Hygiene Window,&#8221; the spores of Bacillus cereus are heat resistant, even when heated to 90°C for 60 minutes.</p>
<p> The same spore-forming bacteria include Bacillus botulinum, which is said to &#8220;produce the strongest toxin&#8221; (Toda), and Bacillus welschii.</p>
<p> Like Bacillus cereus, B. welsh is widely distributed in nature and can cause food poisoning, such as stomachache and diarrhea, even when stewed curry or stew is left to cook and reheated.</p>
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<p> Bacillus cereus is anaerobic and is believed to multiply in the absence of air. According to the Food Safety Commission, the optimal temperature is 43-45°C, but it can multiply in a wide temperature range (12-50°C). Toda points out that curry, stews, meat sauces, and other dishes can cause food poisoning, saying</p>
<p><span class="strongInContent"> It can happen in student dormitories, senior citizen facilities, and other large oven cooking, as well as when large quantities are made.&#8221;</span></p>
<p> To prevent both Bacillus cereus and Bacillus welsh, it is best to eat all cooked food immediately, but the following precautions should be taken if food is left over.</p>
<p><span class="strongInContent"> Quick-freeze or otherwise cool the food so that it &#8220;runs through&#8221; the temperature range at which the bacteria proliferate,&#8221; says Toda.</span></p>
<p> By the way, there is actually another type of spore-forming bacteria that is also edible: Bacillus subtilis natto. It is the Bacillus subtilis natto, or natto bacillus. Mr. Matsumoto explains the bacillus natto as follows.</p>
<p><span class="strongInContent"> It can withstand temperatures of up to 100 degrees Celsius. When the soybeans are heated, other bacteria are killed, but when they are wrapped in straw, the Bacillus natto that was there multiplies. It is characterized by its rapid multiplication.&#8221;</span></p>
<p> This is what makes natto. Please do not think that leftover food that has been cooked and left to eat can be stored at room temperature if it is reheated. Know that there are heat-resistant bacteria.</p>
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 Hideki Asai

 Aflo

 Fried rice syndrome" is a food poisoning caused by cooked food such as fried rice left at room temperature for a long time. Bacillus cereus, which causes this syndrome, is resistant to heat and does not die even when reheated, and actively multiplies at 28-35℃.

What is “fried rice syndrome” that we often hear about these days…?

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