How long can food be unrefrigerated during a walk home from the grocery store?
May 28, 2006 2:11 PM   Subscribe

I have this idea that I want to walk to and from the grocery store to have an excuse to take a long walk (perhaps as long as an hour each way). How long can the walk be before the food becomes unsafe to eat?

I assume that refrigerated proteins have the shortest walk time (fish, eggs, chicken, beef). What about frozen foods? In addition to safety, how about taste? For example, I believe that orange juice tastes worse when exposed to heat. How does the outside temperature affect the walk time? Would buying some kind of insulated bag extend the walk time significantly?
posted by mrkohrea to Food & Drink (33 answers total)
People are going to provide links showing that I am wrong, but I think most food can last an hour if it was fresh to begin with, is grouped together in an opaque bag, was properly refrigerated/frozen before that time, each item is well sealed, and you're going to cook the meat etc. well before eating. Your ice cream is going to melt, but that's about all, I'd think.

I wouldn't worry. Maybe you could take an ice pack with you to help refrigerate stuff on the way home? Or buy one bag of frozen peas for just that purpose?
posted by scarabic at 2:18 PM on May 28, 2006

I don't think one hour will make any real difference to anything, unless you live in a very hot place. Insulated shopping bags are cheap and available though, so buy one if you are worried.
posted by fire&wings at 2:20 PM on May 28, 2006

If you buy yogurt, don't eat it the same day. All of the beneficial cultures will have died as a result of exposure to heat. Leave it in the fridge for at least a couple of days to allow the cultures to (hopefully) regenerate.
posted by invisible ink at 2:22 PM on May 28, 2006

If i remember right, I want to say that eggs don't require refrigeration (technically), and its more of an American thing to leave them in the fridge all the time.

Of course, this doesn't mean you can leave them in the sun for hours, but they should be alright for an hour or so, anyway.
posted by Amanda B at 2:34 PM on May 28, 2006

I have no links, but I do know that people around the world eat many of these items with no refrigeration. I lived in a place without electricity for a couple of years, and so I have some experience with keeping food without refridgeration. Eighty degrees or so outside.

Eggs were absolutely fine - they lasted for a couple of weeks before they went bad. Granted, they were absolutely fresh when I got them, not months old the way eggs in the U.S. are....

Butter was also fine - it lasted a couple of weeks without refridgeration.

Meat lasted a day or so. I never saw anyone keep chicken or milk out at all. Or fresh seafood.

I'd say most things would be fine, though not something like icecream which melts so quickly.
posted by Amizu at 3:04 PM on May 28, 2006

Assuming you're not opening any of the packaging in any way, I'd say probably about a day or two.

Eggs do not need to be kept cold if you plan on eating them this within a week or so. Here in the UK they're not even refrigerated in the stores.

Meat, well, you should be cooking that safely anyway. Not that you should thaw meat on your kitchen counter, but people do it with no ill effects all the time, walking around in a bag shouldn't be an issue at all.

The only thing I could think that might be a problem (in terms of annoyance, rather than health) is if something frozen and shape-able like frozen veggies has enough time to fully thaw, they could end up as a solid and hard to deal with lump when you get them into the freezer and re-freeze them.

Also, some things should not be refrozen because your freezer won't freeze them fast enough to avoid doing damage (and ruining the taste). Shrimp, for example, should really not be allowed to thaw and re-freeze from a taste perspective. YMMV.
posted by tiamat at 3:05 PM on May 28, 2006

Some frozen foods, those with a very low heat capacity I suppose, will not last long at all; other foods will last much longer.

I think refrigerated food will actually fair much better. Sure, it will warm up, it might spend 10-20 minutes at ambient temperature, but that isn't necessarily a big deal.

The weather makes a tremendous difference too, obviously. Why not get a Thermos bad of some sorts, and try to avoid the hottest part of the day in summer - you'd probably do that anyway.
posted by Chuckles at 3:08 PM on May 28, 2006

I usually use 2 hours as a rough estimate for how long foods can be left out at, say, a picnic or something, without ice or refrigeration. I would imagine it to be much the same for unprepared foods, if not longer, since they're still sealed.
posted by fvox13 at 3:11 PM on May 28, 2006

Most of your food should be OK, but why not just buy an insulated bag anyway? That way you don't need to worry about it at all. Here's one. This one looks a little more ergonomic, but also holds less.
posted by Hildago at 3:13 PM on May 28, 2006

Bear in mind the thermal mass of goods. A single chicken fillet will defrost quickly, but 6 of them together will take a long time to warm.

If you're in a hot and sunny climate things may change. On the occasions where I know I can't get to a refrigerator within the next hour or two and I have to buy something perishable like meat or fish, I buy a large bag of peas (cheap) and stick that on top of the perishables. Keeps them cold, and the peas are fine even if they defrost a bit.

If you're cooking your food well, you won't have to worry about bacterial growth in the space of an hour.

I also agree with the idea of buying an insulated bag. Then you won't have to worry too much about things getting warm.

Enjoy your walk!
posted by tomble at 3:21 PM on May 28, 2006

All of the beneficial cultures will have died as a result of exposure to heat. Leave it in the fridge for at least a couple of days to allow the cultures to (hopefully) regenerate.

Pray tell, if all the culture has died, what will provide the source of the regeneration?

It would take a lot more than an hour's worth of walk-about temperatures to kill a yogurt.
posted by five fresh fish at 3:26 PM on May 28, 2006

The guideline that the government uses is that food shouldn't be above 40F for more than 4 hours, so your refrigerated goods should be just fine. Yogurt bacteria won't die in even the hottest parts of the country (it has to be 130F or above to kill it), it will actually become a lot more active as it warms up. Your biggest problem will be with frozen foods, though not from a food safety perspective. Melting and refreezing is detrimental to the texture , meats will lose moisture and veggies will become mushier.
posted by TungstenChef at 3:29 PM on May 28, 2006

Regarding eggs: if they've never been washed, they're okay to keep unrefrigerated, but the eggs you get in the US are washed and therefore are best refrigerated. (I found out about this here and here.)
posted by needs more cowbell at 3:43 PM on May 28, 2006

That is, washing the eggs removes a protective coating that makes the eggs more susceptible to spoilage.
posted by needs more cowbell at 3:44 PM on May 28, 2006 [1 favorite]

IMO I don't think you have any reason (safety or taste) to worry about a one hour walk with your groceries, even in the middle of summer, but then I reheat rice...

But as you are worried, why not walk to do your main shopping, as you want to do, but do a once-a-fortnight drive / cycle / bus to the store specifically for meat and icecream?
posted by bella.bellona at 3:45 PM on May 28, 2006

Someone above suggested an insulated bag. That's a good idea. Moreover, I'd suggest some kind of stroller that can carry a small-ish cooler with ice packs.
posted by frogan at 3:48 PM on May 28, 2006

five fresh fish- you're right, I'm wrong. I didn't mean every single live and active microorganism. But since refrigeration helps keep the number of cultures at its maximum number, I still recommend leaving the yogurt in the fridge for a while to allow them to multiply and grow. If you tend to eat yogurt later in the day (i.e. when your level of stomach acids is at its highest), those acids can kill off a good number of the friendly bacteria. So you want to begin with as many of those cultures as possible.

it will actually become a lot more active as it warms up.
Really? If you have a link on hand, I would be interested in seeing it (note: not trying to be snarky, if I'm wrong, then I'd like to be corrected so I don't continue misinforming others.)
posted by invisible ink at 4:12 PM on May 28, 2006

Walking for an hour with bags of heavy shopping? That's going to be hell. My walk from the supermarket is 15 mins, and even with a rucksack I'm exhausted once I get back with a weeks worth of food...
posted by Orange Goblin at 4:28 PM on May 28, 2006

I'd be more concerned about how tired your arms will get carrying groceries for an hour. Frozen food, milk, poultry and meat won't do well. Most other foods will do okay for an hour, especially if you get an insulated bag. Veggies, fruit, bread and other fragiles may smushed.
posted by theora55 at 4:31 PM on May 28, 2006

invisible ink, see Making Yogurt at Home; which speaks of growing bacteria culture for yogurt at betwen 90 and 120F (32 to 48C, by my calculation).

Most all bacteria do better at higher temps, just about right up to when it kills them off.
posted by tiamat at 4:31 PM on May 28, 2006

3 lousy minutes. *waves at Orange Goblin*
posted by theora55 at 4:32 PM on May 28, 2006

I've taken almost all the foods mentioned backpacking or camping, meaning that they were un-refrigerated for at least a day before I ate them and I haven't died yet. Ice cream will probably be your major casualty, that stuff goes mushy even when I drive to the store.
posted by fshgrl at 5:04 PM on May 28, 2006

A lot of people seem to be advising buying a thermos bag, even though it's pretty well agreed all your food will be safe. That's just silly. We USAians have forgotten how recent refrigeration is, and how well most of the world does without it. Don't worry about spoilage. But do worry about your hands and shoulders. In New York, small folding wheeled carts are a must for grocery trips (unless you're having it delivered). But don't buy what's not necessary.
posted by rikschell at 6:28 PM on May 28, 2006

This isn't answering the question exactly, but instead of walking a long way to a distanct grocery store, why don't you choose a local store? Go for a long walk that ends at the store, and then walk the short distance home. You still get the walk, still get the shopping, and don't have to worry about spoilage.
posted by twirlypen at 6:34 PM on May 28, 2006

Yeah, can you configure your walk so that you walk for an hour or two and then hit the grocery store?
posted by occhiblu at 6:37 PM on May 28, 2006

But since refrigeration helps keep the number of cultures at its maximum number, I still recommend leaving the yogurt in the fridge for a while to allow them to multiply and grow.

No, no, no. The refrigeration stops them from multiplying. That's the whole purpose of refrigeration. The cooler the temperature, the "sleepier" the bacteria get. The warmer, the more they frolic and reproduce.
posted by five fresh fish at 6:39 PM on May 28, 2006

The only thing I can think of that would really suffer would be ice cream and shrimp, echoing comments upthread.

Are you only shopping for yourself? With an occasional big trip for staples and heavy items, you should be able to easily carry one week's worth of food, unless you buy a lot of processed overpackaged stuff.
posted by desuetude at 7:03 PM on May 28, 2006

I walk to the grocery store.
If buying something like icecream, consider that you could also walk to a closer supermarket and make two trips, so you don't have to carry as much per trip (or can carry more in total than you could otherwise, depending on how much you need to buy), and still get a couple of hours on your feet but the food is only unrefridgerated for 30 minutes, which is the norm in many places for people using a car.

Also, carrying too much, even if you can do it without discomfort, can be hard on the spine, and you need that spine for everything in life that you do. For that reason, I'd suggest two shorter trips unless you're not buying much - enough weight to help with the exercise, without putting undue strain on the spine.
posted by -harlequin- at 8:07 PM on May 28, 2006

Refreezing thawed food isn't just unsavoury, it is also presents the greatest risk for food poisoning. Especially refreezing melted ice-cream.

For almost all other foods, however, exposure for an hour to ambient temperature will be harmless, assuming that you aren't immune compromised (e.g. suffering from AIDs).

There is bacteria everywhere that might make your food smell bad but is otherwise harmless -- so long as you minimize the anaerobic kind and the fecal coliforms, the risk of serious food poisioning is minimal.
posted by randomstriker at 8:47 PM on May 28, 2006

Get a stroller, red wagon or what ever you can find with wheels to get to and from the store. If you have a wagon or big enough stroller you can take a cooler for the frozen items. Don't worry about the rest.

wife of 445supermag
posted by 445supermag at 8:55 PM on May 28, 2006

Your food will be fine unrefrigerated for an hour but your arms will be wrenched from their sockets if you carry all that stuff in a bag. Some kind of wheeled cart or wagon would help a lot, as Mrs 445supermag says.

How about big pannier bags for your bike? Hubby and I routinely go grocery shopping on our tandem trike, which has big panniers for exactly this reason. (By the way, the food sits in the bags for about an hour and it's fine when we get home. If ice cream is on the list we bungee a cooler to the rear rack; otherwise we don't worry about it.) If you ride your bike to the store, you get exercise, the bike carries the weight, and you get home faster - what's not to like? (If you're a non-bike-riding spaz like me, get a trike!)
posted by Quietgal at 9:53 PM on May 28, 2006

Okay, I stand corrected.
posted by invisible ink at 10:10 PM on May 28, 2006

Feh. I do this all the time--it's about one-and-a-half or two miles, through extreme rural conditions, to the store. Don't even worry about the food spoiling or whatever. But I agree with two magic words: Back. Pack. (Particularly if you're carrying live lobsters. Heh. Nothing worse than grocery bags with claws on a long haul.)
posted by RJ Reynolds at 11:51 AM on May 29, 2006

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