Are you packing Japanese-style bento for your children or for work? Here are helpful food safety tips on keeping the lunch safe until lunchtime.
Bacteria can grow rapidly in a warm environment, which can cause food poisoning.
Don’t worry, I don’t mean to scare you. I brought homemade bento that my mom prepared every day to middle school, high school, and college, and I never had food poisoning.
To make sure the food is safe for those you pack lunches for, you should follow the following 3 key points: cook/reheat, let cool, and keep it cool till lunchtime.
Why We Reheat Food
Japanese bentos are meant to be eaten at room temperature. The fact is the longer food has been lying around, it gets less fresh, even if you put an ice pack or keep it in the refrigerator.
Therefore, I highly recommend reheating cooked food before packing lunch. Reheating cooked food kills bacteria. It’s better to take extra safety precautions especially if you live in a humid or hot climate.
All you need to do is to reheat the food, let it cool down completely before closing the bento box, and then keep the bento cool with an ice pack the whole time with till lunchtime.
However, if you can keep your bento box in the refrigerator and microwave it at lunchtime (such as in the office), it is okay to pack lunch the previous night and keep it in the refrigerator.
Read more about food poisoning and food spoilage here.
How To Keep Your Bento Safe
Before Packing
- Wash your hands.
- Make sure your bento box is clean and dry.
While Packing
- Use clean utensils (chopsticks etc) or plastic gloves when you touch food. Your hands carry germs so it’s better to avoid handling food with bare hands. If you touch one food to the other with the same utensil, wipe off the utensil in between, or simply use another utensil. If you decide to wash it, then make sure your utensil is completely dry before picking up another food.
- Re-heat pre-cooked/leftover food before packing is highly recommended. If you do so, I also recommend heating up with a pan or toaster oven instead of microwave so that food, especially meat, is heated THOROUGHLY and not partially.
- Before you pack cold/cool food in your typical Japanese bento box, hot/warm rice must be cooled down. It’s dangerous when hot/warm rice heat up other food halfway because bacteria would start growing.
- Remove all liquid from the food which could spoil faster.
After Packing
- To avoid any risk of bacteria growth, you must cool down the food first before closing the bento, especially if the lunch box is going stay at room temperature for a few hours period.
- Use ice packs and an insulated bag to keep food fresh and safe till lunch time.
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Hi Namiko! I’ve been super interested in new cooking styles lately and I have made some of your recipes. As I was reading about your bento boxes, I noticed you mentioned they are meant to be at room temp. This is important for me because I have very sensitive teeth. But then you mention heat/reheat, cool, then pack. But I was wondering if you could be a bit more specific. Let’s suppose you were going to make an egg to put into a bento box, what are the steps you would take to do that safely? I’m just wanting an example for the process. Thank you so much for your content!
Hello, Emily! Thank you so much for taking the time to read Nami’s post!
If you are preparing an egg in the morning, let it cool on the plate or cooling rack before packing it into the Bento box. If you live in a hot location, we recommend packing the Bento box with an ice bag to keep it cool.
Reheating is only necessary when you use a day-old dish or frozen product.
We hope this helps!
Hi Namiko! Thank you so much for the helpful guide and inspirational recipes.
I’ve been preparing bento lunches for my kindergartener for a few years now but as the duration of the time the food is being packed and time of consumption is about 3hrs, I wasn’t too concerned about the food safety. However she has now started Elementary school and the duration of the time the food is packed till time of consumption is about 5hrs, I’m nervous about whether the packed bento would have somewhat gone bad. We live in Malaysia where its hot and humid.
I’m not sure if packing the bento box in an insulated bag with an ice pack inside would help keep the food safe for 5hrs till lunchtime.
Hi Lynn, Thank you for reading Nami’s post!
We recommend using bigger ice packs than now or packing the frozen jelly (Kids enjoy little dessert, and it works well) inside the bento box to help keep the inside temperature low. To be safe, how about testing the bento box before school starts? So you can be sure the Bento is at a safe temperature at lunchtime. Different humidity and temperature might result differently.
We hope this helps!
I still do not understand the logic behind reheating. For this example, let’s say I prepare the food on Sunday and Monday. Monday at 8am I prepare the Bento, and at 1pm I want to eat it.
Let’s remind ourselves of the “danger zone temperature” that is explained somewhere here, i.e. the temperature where leftover rice can grow bad bacteria (between 5°C and 60°C)
On Sunday evening, I cook rice with a rice cooker. In the rice cooker, the rice is obviously steaming hot. I take it out and spread it out on a large area to let it cool down. After it’s cool, I should put it in the freezer immediately to get the rice below 5°C. That means the only “danger time” was while cooling down for about 20min.
On Monday at 8am, I take out the rice from the freezer. Let’s say I also take out a leftover slice of chicken. According to the article, I now need to reheat both to at least 60°C to kill bacteria.
But then you tell me to let everything cool down to room temperature to pack them into the Bento. Which brings both into the danger zone! If I eat the Bento at 1pm, the Bento could have been in the danger zone temperature for as long as 4 hours!
And at 1pm, am I supposed to reheat the Bento AGAIN? Otherwise I am eating bacteria that have grown during the 4 hours!
Please help!
Hi Mike! Thank you very much for reading Nami’s post!
To keep your Bento box safe, Please do not forget to use an ice pack after cooling it down. Reheating is to kill bacteria, and an ice pack is to keep the food safe until lunch.
Here is the recommendation from USDA, and we hope this helps.🙂
https://www.usda.gov/media/blog/2019/08/13/use-insulated-lunch-bag-keep-meals-safe#:~:text=According%20to%20the%20U.S.%20Department,a%20safe%20temperature%20until%20lunchtime.&text=Foodborne%20illness%20can%20multiply%20rapidly,F%20and%20140%C2%B0F.
Hi Namiko! Thank you so much for the helpful guide…just one question, but do you usually let the rice cool in the rice cooker before packing it into the bento box, or is it okay to put it directly into the box after it’s done cooking?
Thanks so much!
Hi Tori! Thank you very much for reading Nami’s post!
We recommend taking out the rice on a plate to let it cool for minutes, then pack them into the bento box to avoid the condensation inside the bento box.
We hope this helps!
Hi Namiko! Thanks a lot for your recipes! I’m planning to do more of meal prep, I’ve read your tips, but still have a few questions: if I store food in the freezer, do I have to reheat it, cool down and then pack? It’s for office lunch, we put it in the office fridge as soon as we get to the office, in about an hour. And some foods for my bento will be from the freezer, some may be from the fridge, so not frozen.
Hi Svetlana! Thank you very much for reading Nami’s post and trying her recipes!
If that is the case, you can bring your frozen food/bento with an ice pack to the office and place it in the fridge at work. Then you can reheat it at lunchtime.
We recommend reheating them either at home or office before you eat.
We hope this helps!
Hi, I have read that cooked rice should be consumed within 2 hours after cooking it when stored at room temperature but it’s quite unrealistic to consume a bento after only 2 hours. Even if I cool the rice before in the fridge (4°C) it will heat up quickly during the day (so maybe I can extend the period by 1 hour). So how long is it really safe to eat the rice? This makes me really anxious because of bacteria that create toxins (which don’t get removed when reheating either).
Hi Manu, Thank you very much for reading Nami’s post!
As Nami mentioned in this post, we recommend using ice packs to keep food fresh and safe till lunchtime. You can also use an insulated container to keep your food hot until lunchtime. 🙂
Here is the recommendation from USDA. We hope this helps!
https://www.usda.gov/media/blog/2019/08/13/use-insulated-lunch-bag-keep-meals-safe#:~:text=According%20to%20the%20U.S.%20Department,a%20safe%20temperature%20until%20lunchtime.&text=Foodborne%20illness%20can%20multiply%20rapidly,F%20and%20140%C2%B0F.
Hi Nami, can I reheat already cooked rice and then use it for bento? I just have to make sure that it is cooled down before packing it? I am planning to pack bentos for my daughter when she starts school. Bento will be packed at 7am and she will eat at 12pm. I am probably going to add an ice pack in the lunch box. I live in northern california. Thanks!
Hi Joy, Thank you very much for reading Nami’s Post.
If you are packing the reheated rice for the Bento box, we recommend first you freeze the cooked rice when you cook. Then you reheat them in the morning, let them cool, them pack for the Bento. https://www.justonecookbook.com/how-to-freeze-rice/
As you mention, if it’s a warm day, the ice pack will be a good idea. Please note that reheated rice will not last long, so we recommend enjoying them at lunchtime and not in the afternoon. We hope this helps!
Hello! Thank you so much for posting this, it’s helped me understand a bit more about how to pack a bento box better. I do have a few questions though
I am starting to become a morning person and this all sounds great but I’m actually unsure of how long it would take to cool everything down. How long does it usually take for you?
Are there any quick ways to cool things down if I were rushing?
Also, I use jasmine rice, is there anything I can do to make it stay moist? I find it gets dry very easily, could I use rice vinegar and mix a bit in? Or season it with some salt first?
Another question I have is the ice pack if I am not planning to eat the food til lunch or from lunch – dinner, won’t the ice pack make it a bit moist if I have lettuce or tomatoes in there?
Hi Carmen! Thank you for your kind words!
1) I cook bento first then breakfast and kids pack up their lunch right before they leave the house – that means they have minimum 1 hour.
2) To speed up the process, you can use an ice pack to cool down instantly. Many Japanese moms do this technique to let the food cool fast.
3) I don’t eat Jasmine rice because of the dry texture. It’s just the type of rice. It’s great for fried rice (separate easily!), but not great for bento and Japanese foods… Unless you’re making sushi, DO NOT season your steamed rice with vinegar/sugar/salt (we call sushi vinegar or sushizu). Vinegared rice is ONLY for making all types of sushi. NOT including even Onigiri (rice balls). Please use Japanese rice when making sushi and onigiri because the rice will not stick to each other and it will be a complete mess with separated rice kernels.
4) Possibly – the ice pack is to keep it cool, so adjust the size or amount of ice packs. You don’t want your lunch to be cold… 🙂
Hope this helps!
2)
Hello Nami. I’ll be joining the bento/lunchbox making next year when my daughter goes to Kindergarten here in States. I love packing Asian food, including Japanese recipes (i.e. teriyaki salmon, rice and karaage etc), as lunch. Would you recommend me to re-heat the morning I pack and let it cool before I put it in lunchbox and an ice-pack in the lunch bag so it stays cold for safe consumption? Is it safe to eat cooked meat/fish cold (from ice pack)?
Can you also let me know what lunchbox do you use for your kids? I’m thinking Thermos foodjar for hot and liquid food while cold food (i.e. fruits) and snacks in a plastic/stainless steel lunchbox. Can you also recommend me which lunch bag fits for cold and hot lunches?
Thank you so much.
Hi Wendy! Aww your daughter is going to Kinder! I miss those days!
In Japan, we always reheat the food in the morning for food safety (kill any possible germs – even you kept in the fridge). People here may practice differently but I packed my own lunch growing up in Japan and I just do as a habit. If you bring to your office and microwave there, then you can transfer cold lunch box from home to office and there is no issue there… but kids can’t reheat the lunch at school.
Japanese kids/adults are used to eating lunch at room temp. I put the ice pack under the fruit box, so it’s mostly for the fruits and entire lunch box not to go too warm. I used Japanese character lunch boxes when they were in Kinder and maybe 1st/2nd grade, and then shift to Lunchbot (stainless steel). I also use food jars from Thermos too. In my shop page, I put the link for kids’ lunch bag and bento boxes links. Hope that helps!
I’m fine with her eating room temperature food. Just to clarify, is the reheated food with ice pack underneath will be room temperature/cold when it’s lunch time?
I heard so many good things about Lunchbot. Is it manageable for a 5yo?
Hi Wendy! My kids had a smaller lunchbox when they were 5. It also depends on what you pack in – if it’s some food and snacks that are easy to eat, a Lunchbot size will not be an issue. But I put rice in half of bento and Lunchbot was a bit too big for my kids that time to eat in 15-20 minute lunch break.
I don’t know what size is your ice pack, but I put a small ice pack underneath the fruit box and I do not put ice packs underneath the Lunchbot unless it’s a sandwich that includes deli meat. 🙂
Nami, how long for food that is reheated and cool before packing safe to consume assuming that the food is already at room temperature when it is packed?
Typically, moms cook bento between 6 to 7 am, and kids eat around noon. So 5-6 hours? If you’re in a humid climate, food goes bad faster, so I recommend creating a cooler environment in the lunch bag. Growing up, without the ice packs in my lunch bag, I never had any issue. Japanese moms make lunch every morning and kids bring to school at room temperature. In summer, the menus are considered to make sure they don’t go bad. Stronger taste, umeboshi in rice, salt use in Onigiri etc…
Good to know. I live in Chicago so I won’t have to worry about hot and humid environment. Thank you so much, Nami.
Hi Wendy! Great! Good luck with your bento making! xoxo