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Food safety for packed lunches (old and new wisdom)

A major concern when packing lunch is making sure the food won’t spoil by the time it’s eaten. I’ve been doing some research on the different methods Japanese and Americans recommend for safe packed food, to reconcile traditional wisdom with new methods and research on foods with antibacterial properties. There are many different methods, I’ve described them in detail below with sources. These are only guidelines for food safety; please make your own decisions about what you’re comfortable packing and eating (I am not a food safety authority).

An outline of methods to ensure your packed lunch won’t spoil (details behind the cut):

  1. Incorporate food and products with antibacterial properties
  2. Keep it clean: Don’t introduce bacteria into the lunch when packing
  3. Keep hot foods hot and cold foods cold, using thermal jars and cold packs
  4. Pack less perishable foods, especially in the summer
    • Extra precautions for hot weather
    • Handy foods for hot weather
    • How to make dishes less perishable

1. Incorporate food and products with antibacterial properties

Japanese bento cookbooks often suggest packing foods with antibacterial properties in lunches in order to keep food from spoiling. Suggested foods include umeboshi (pickled plum), wasabi, ginger, karashi, salt, shiso, parsley and vinegar (i.e. making sushi rice, or putting an umeboshi or a tablespoon or two of rice vinegar in the cooking water when making rice). Some books recommend wiping the inside of the bento box with a slice of ginger before packing.New USDA- and NSF-funded research on foods with antibacterial properties has yielded a number of additions that are interesting when packing non-Japanese food for lunch. The strongest antibacterial foods (killing all bacteria) are evidently garlic, onion, allspice and oregano. The second strongest (killing up to 80% of bacteria) include thyme, cinnamon, tarragon, cumin (and lemongrass). The third strongest (killing up to 75% of bacteria) are capsicums, including chilies and hot peppers. The fourth strongest (killing 25% of bacteria) include white and black pepper, ginger, anise seed, celery seed, and lemon or lime juice. Honey has antibacterial properties, and the dodecenal compound in cilantro/coriander (both fresh leaves and seeds) is evidently one of the stronger antibacterials as well. (see sources 1 - 3 below)

There are a number of bento products in Japan that have been treated with an antibacterial coating (i.e. flavorless compounds extracted from wasabi, etc.), designed to help stave off microbial growth in packed lunches. These include aluminum food cups for cooking, plastic sheets that you place on the surface of your packed food, and food dividers (”baran”) that look like sushi grass. These must be touching the surface of the food to be effective. I bought the products below at local Japanese dollar stores and markets in San Francisco; click the photos for larger views and details. EDIT: Not all food dividers and food cups are antibacterial; they must have the Japanese characters that mean “antibacterial” on them (click the product photos below for a larger view with the appropriate characters pointed out in a note on the photo).

Antibacterial food dividers and bento sheets:
Antibacterial lunch dividers and bento sheets Antibacterial bento sheet in action

Antibacterial cups:
Antibacterial food cups


2. Keep it Clean: Don’t introduce bacteria into the lunch when packing

Make sure your hands, food prep area, utensils and lunch containers are clean. When possible, use utensils (chopsticks, spoon, tongs, plastic wrap) to place, mold and arrange unwrapped food in your lunch container. If you’re using a bento box with a rubber packing strip around the lid, be sure to periodically remove, wash and thoroughly dry the packing seal (and the groove in the lid). This will keep your box clean and ensure that the packing strip does not crack, which would leave you without a watertight seal.

3. Avoid the temperature danger zone with perishable foods


4. Pack less perishable foods, especially in the summer. Rice becomes hard and unappetizing when refrigerated at low temperatures, so many Japanese forego refrigeration and cold packs for their rice-based bentos, choosing instead to incorporate antibacterial foods, pack foods that are less likely to spoil, and make their food less perishable through traditional cooking/packing methods.

A. Extra precautions for hot weather


B. Handy foods that survive summer heat


C. How to make dishes less perishable

Sources:
1) 1998 Cornell study on antibacterial spices: http://www.news.cornell.edu/Chronicle/98/3.5.98/spices.html
2) Cilantro article: http://www.eurekalert.org/pub_releases/2004-05/acs-is052404.php
3) CookWise, Shirley O. Corriher, 1997.
4) The New Professional Chef, Culinary Institute of America
5) USDA lunch food safety guidelines: http://www.cfsan.fda.gov/~dms/ftteats.html#lunch
6) USDA Freezing/Refrigerating time chart: http://www.cfsan.fda.gov/~dms/fttstore.html
7) Aijo Tappuri! Obento, Shufu no Tomo, 2007.
8) Obento Daijiten, Index Magazine, 2005.

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38 Responses to “Food safety for packed lunches (old and new wisdom)”

  1. sff_corgi Says:
    December 31st, 1969 at 5:00 pm
  2. pinkfairywand Says:
    March 27th, 2007 at 8:15 am

    This is just the post I’ve been waiting for!

    As always, you’ve taught me something. I really appreciate this handy guide, since my bento boxes will arrive this week.

    The antibacterial food section is easily the most interesting thing I’ve heard in a while (so far as food goes), and I can’t wait to try implementing them into my rice and lunches.

    Thanks a ton!

  3. pure_trance Says:
    March 27th, 2007 at 11:12 am

    I was actually going to post a question regarding this on bentolunch…thanks :D

  4. gatekeepers_21 Says:
    March 27th, 2007 at 12:20 pm

    This is very helpful! Thank you (:

  5. ss_biggie Says:
    March 27th, 2007 at 6:08 pm

    Glad you got something out of it! I found the antibacterial food info to be fascinating — if you think about it, it starts to explain the foodways of different cultures (spicier foods in hotter climates).

  6. ss_biggie Says:
    March 27th, 2007 at 6:09 pm

    Guess we’re on the same wavelength!

  7. ss_biggie Says:
    March 27th, 2007 at 6:10 pm

    My pleasure. Good for me to research as well, as I don’t want to make Bug sick (but sometimes keeping lunch cold until we’re ready to eat it isn’t feasible).

  8. otana Says:
    March 27th, 2007 at 9:03 pm

    When you say “regular tofu”, what do you mean? As in, straight out of the pack? I have some extra-firm tofu that we had for shabu-shabu; I put the leftovers in the broth to cook through, then packed it in the fridge in tupperware for bentô later, is that okay, do you think?

    I love the idea of freezing canned fruit, I use a lot of it for lunches and the idea of using it as a cooling pack is awesome.

  9. yumimb Says:
    March 27th, 2007 at 10:24 pm

    This is seriously like a grad school research paper or even a thesis! Thanks! One question - where can I get cool packs here? I used to re-use the ones I got from cake shops (they will give you mini-cool packs so cream won’t be melt while you take the box home) when I was in Tokyo.

  10. anonymous Says:
    March 28th, 2007 at 12:46 am

    Thanks for the great info. I love that you add your “sources”. My daughters lunch had condensation on the lid today…and zero on the antibacterial foods. Are obentos meant to be eaten at room temp or cool? I’ve only added an icepack to her lunchbox when she has yogurt or cheese in it. Now I’ll be more careful. I wonder if that’s why they add salt to onigiri? So fascinating! I’m sure people thought more about this before refrigeration was available! –julie

  11. ifitmakesubettr Says:
    March 28th, 2007 at 6:56 am

    Wow, thank you so much, amazing!

  12. ss_biggie Says:
    March 28th, 2007 at 8:16 am

    I meant not the agedofu, fried tofu or dry tofu skins. Some of my Japanese bento cookbooks warn against regular tofu (including extra-firm) because it sheds water into the bento and spoils easily. I’d say it depends how you pack it: does it get its own little container so moisture won’t get all over, say, your rice and other items in the box? Are you going to keep it cool until you eat it (or are you going to eat it within three hours of packing it)? If so, go for it.

  13. ss_biggie Says:
    March 28th, 2007 at 8:27 am

    My pleasure!

  14. ss_biggie Says:
    March 28th, 2007 at 9:04 am

    Thanks! I’m not a food safety expert, so I thought people would like to see where I got the info (I didn’t just pull it out of my ear). If there was condensation on the lid, that would probably be because you packed food while it was still warm and closed the lid on it before it cooled totally. Happens to me sometimes too. Japanese bento cookbooks would advise against that, especially for preschoolers, as it makes the lid hard to open in addition to the food safety issue.

    Traditionally bentos are eaten at room temperature, but there’s a new trend in Japan towards better food safety (insulated bento bags/kits, antibacterial products, more focus on antibacterial foods, etc.). Salt in the onigiri is, in fact, a way to keep the rice from spoiling — I found that very interesting!

  15. otana Says:
    March 28th, 2007 at 1:21 pm

    I had a feeling that’s what you meant, just checking. ;)
    Yes, it would be packed separately, or rather with the rest of the shabu shabu veggies in their own water-proof pack. The bentô is for my other half, she prefers to keep hers refrigerated at work, so I guess there’s not a problem?

    Appreciate the advice, by the way!

  16. robynchick Says:
    March 28th, 2007 at 1:44 pm

    Great Bento tips!

    I wonder, where are the good japanese dollar stores in San Francisco? I live in the Bay Area and I’ll be visiting the city this weekend. Any favorites, or stores that are easy to find and park at?

    -Robyn

  17. ss_biggie Says:
    March 28th, 2007 at 1:56 pm

    Two that you *must* hit: 1) Ichiban Kan in Japantown (next to Peace Plaza) — most everything for $1, and they have a bunch of egg molds (2 for $1.50!) and insulated bento sets in stock right now. Also the antibacterial bento sheets (a package of 60 or so for $1), little sauce containers, the Urara line of bento boxes and accessories, Feel at Ease line (bento oxes, collapsible sandwich cases, chopsticks & case, bento bags, water bottle bags), and the Simple Color (?) line accessories with lots of bento bands, etc. Parking’s not good, but it’s worth looking. As long as you’re in Japantown anyway, then go across Peace Plaza and find Moritaya, where you’ll find a lot of very unusual (but extremely overpriced) character bento boxes and accessories. Think Totoro, Anpanman, Thomas the Tank Engine, Miffy, Monokuro Boo, Pokemon, etc. Be sure to look all over the store, not just the rear left corner. Daikoku by Shiki on the same floor as Moritaya (by the entrance) has some Hakoya boxes in the back.

    2) The ultimate: Daiso in Daly City at the Serramonte Mall, across the parking lot from Target. At over 15,000 square feet, it’s currently the largest Daiso store in the U.S. Everything’s $1.50 unless otherwise marked. Depending upon where they are in their inventory cycle, you can hit the bento jackpot here. Look all over the store, not just the bento area right behind and to the right of the cash registers (go in the back room with all of the plastic freezer containers).

  18. ss_biggie Says:
    March 28th, 2007 at 1:58 pm

    Sounds like a smart way to pack tofu to me!

  19. ss_biggie Says:
    March 29th, 2007 at 1:17 am

    Mostly I reuse ones that I get from other packages, but I know that Target has some cute ones for kids (SpongeBob Squarepants, etc.) and ugly/plain ones for adults. If anyone in the Bay Area knows of a good source (especially for small ones), chime in!

  20. amvn Says:
    March 29th, 2007 at 5:06 am

    Awesome, I love that you took the time to post this, it was really helpful! I love the idea of a rice-’lid’, now that I got my thermal bento it’s almost my favourite one, because I think warm food is so comforting.

  21. girlwhowaits Says:
    March 29th, 2007 at 5:19 am

    That is very informative. Thanks!

  22. ss_biggie Says:
    March 30th, 2007 at 4:21 pm

    I’m so glad this is getting read; sometimes I worry when I see photos of bento lunches with spoonfuls of yogurt in them (are they being refrigerated?). I do like the little thermal bento, but the little regular boxes are also nice when I’m carrying multiple lunches (me and Bug) as they’re smaller. I’m happy to have the option.

  23. sff_corgi Says:
    March 31st, 2007 at 7:17 pm

    I’ve been thinking those novelty reusable ice cubes would be good for bento (I live in Miami, everything gets hot), but they’re not as easy to find as I thought.

    The plain cubes, the ones that look like miniature baggies, however, are easily obtained and could serve for portable refrigeration if there’s no frozen items in one’s meal that day.

  24. quiet000001 Says:
    March 31st, 2007 at 9:03 pm

    I’m just discovering this community so I’m reading back a bit- Anyway, when I lived in the UK and we got meat delivered sometimes from an organic place, they used re-useable cool packs which were basically filled with that stuff you get in garden stores to put in your soil to hold moisture. (They’re little pellet things and they swell up when you put them in water. I forget what it’s called- gets sold for use in potted plant soil particularly since you have to water less often.)

    I wouldn’t trust the stuff to be food safe in terms of using it directly in contact with food (ew) but I suspect you could whip up your own little mini cool packs with that stuff and a plastic baggie or two. (Just make sure to allow expansion room in the baggie before you put it in the freezer.) Since the stuff is quite squishy, you could even freeze it to fit around/between specific containers.

    (If you were going to use it in a box for a kid unsupervised, you might want to tape the baggie shut- I’m pretty sure the stuff is non-toxic to touch, but I don’t think you’d want someone eating it. :) )

  25. ss_biggie Says:
    April 1st, 2007 at 8:22 am

    Out here in San Francisco, I tend to see them in the summer at stores like Target, but I would have thought they’d be much more common in Miami. Good luck, and good tip, sff_corgi!

  26. ss_biggie Says:
    April 1st, 2007 at 8:25 am

    Hmm, interesting work-around, quiet! I agree that I wouldn’t trust it next to food or for a child, but it’s still interesting.

  27. sff_corgi Says:
    April 1st, 2007 at 2:59 pm

    You would think, wouldn’t you? But the big stores like Target don’t seem to realise their seasonal inventory doesn’t work well down here (Mittens? Why? We need mosquito coils, guys) and never skew for our conditions.

    Can’t find any good novelty shapes on-line other than hearts and porno shapes, alas; it’s mostly ice cube trays I’m finding. I haven’t hit up any local-local stores yet because I’m not sure where to look, and major producers would have their product in on-line stores anyway. Is *sigh*.

  28. quiet000001 Says:
    April 1st, 2007 at 4:25 pm

    I think it’d be best if you wanted a cold pack to go outside your bento box, but inside a thermal carrying bag- no direct contact with the food, and you could for example mold it around an empty bento container in the freezer, so it’d come up around the sides and not just only touch the bottom.

    Also, I remembered that I’ve seen small cold pack things in the first aid section of a lot of places, in various cute characters. (I know I’ve seen a Mr. Men one.) I think the idea is if the ice pack is neat, the kids get less upset about being hurt? :) But they’d work just as well for keeping a lunch cold. :) So there’s a section of the store to check out.

    (Someone mentioned reuseable ice cubes, too- in my experinece they don’t stay frozen really very long. I’d do test runs before relying on them to keep something cold for several hours.)

    Another tip which occured to me is to remember that not only do you want something with your food to help it maintain temperature (hot or cold) but you want to insulate it from the outside temperature, too- and one of the better ways to do that is trapped air. So if you don’t have a thermal bag (or want to give it some extra protection) a trick is to wrap your container with something with loft- a terry cloth towel with some thickness to it, or a bit of blanket, for example- before putting it in your carrying bag.

    (That’s the trick my mother in law taught me for defrosting the freezer, actually. :) Line some cardboard boxes with a couple of blankets or a few towels, and wrap up your frozen food and it’ll all stay nice and frozen long enough for you to deal with the freezer.)

  29. quiet000001 Says:
    April 1st, 2007 at 4:30 pm

    Ah. YOU have all the mittens. Meanwhile not long ago we had a ridiculous cold spell and I could find summer hats and bathing suits and beach towels, but could I find a warm pair of gloves or a winter hat? No.

    I mentioned in another comment, but I’ve seen some small cool packs in the first aid section of drugstores, so maybe try there?

  30. sff_corgi Says:
    April 1st, 2007 at 4:38 pm

    Yes, and they also put up Christmas decorations a fortnight before Halloween.

    Hmm, first aid items. Good idea. Not decorative, alas, but a good idea.

  31. quiet000001 Says:
    April 1st, 2007 at 4:51 pm

    Actually, I’ve seen some kind of cute ones aimed at little kids- not necessarily food themed, but I think I’ve seen a soccer ball one and a flower one, and there are probably character ones floating around (I mean, they’ll put Disney Princesses on everything ELSE. :) )

    If you were feeling crafty, I suppose you could also make decorative little ‘pillow’cases for the boring looking cold packs out of napkins/cotton fabric. A thin layer of cloth like that shouldn’t interfere with the function of the cold pack.

  32. sff_corgi Says:
    April 1st, 2007 at 5:02 pm

    …!

    Oooo… you’re good.

  33. ss_biggie Says:
    April 2nd, 2007 at 12:54 am

    Good tips on the first aid section for cold packs, and wrapping your lunch to insulate it. Japanese often do this with “lunch cloths” or furoshiki. The traditional bento-wrapping style is illustrated here as “Otsukai Tsutsumi”:
    http://www.env.go.jp/en/focus/attach/060403-5.html (this how-to chart was produced by Japan’s Ministry of the Environment as part of an effort to reduce disposable bag waste).

  34. anonymous Says:
    April 4th, 2007 at 10:58 am

    Thanks so much!
    I made it only to Ichiban Kan this time. Maybe I’ll get to Daiso next time, but I got TONS of stuff and so did my boyfriend!

    I got a new bento with an insulated container, an onigiri/musubi mold, 2 egg molds, little flying pig sauce containers, a bunch of nori and a couple elastic bento bands to hold it all together.
    great tips!

  35. anonymous Says:
    April 4th, 2007 at 11:24 am

    Just a hint, I find those cute ice cubes at my local ross. I saw them in fish shapes, and flamingo shapes!
    I dunno if you have a ross out there, it’s a lot like marshalls and other department discount stores.

  36. sff_corgi Says:
    April 4th, 2007 at 12:34 pm

    [kicks LJ's Schwartz in the tuchus for database errors]

    Try, try again. Sorry.

    Oh, we definitely have Ross down here, for quite a few years now. And Marshalls, and I think there’s even a Burlington Coat Factory but only at Sawgrass Mills (coat stores do tyres??). Thanks for the tip!

    A work friend said the dollar section at Target, the display always right by the mail entrance, also has reusable cubes often. I haven’t made time to stop by and check yet, though.

    I guess they’re just too cheap an item to show up on-line…?

  37. ss_biggie Says:
    April 5th, 2007 at 2:36 am

    SCORE! I’ve noticed that Ichiban Kan is really increasing their bento-related inventory lately, and not with just the same old stuff. I wonder if this is how they’re responding to the presence of Daiso nearby… Hey, the consumer wins in this battle, right?

  38. ss_biggie Says:
    April 10th, 2007 at 5:13 pm

    I just put together an opinionated shopping guide for bento-style gear in the Bay Area I hope you got a chance to read.

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