How are these pouches/boxes of food shelf-stable without refrigeration?
August 27, 2017 1:18 PM   Subscribe

I don't understand how you can put curry or soup on a shelf at room temperature for months at a time without any preservatives and it still be safe to eat. I enjoy the convenience of these items, but it kind of freaks me out. Can anyone explain? Specific examples after the jump:

Sometimes I buy shelf-stable food that comes in a silver pouch or in a cardboard-type box. For example...

• Trader Joe's madras lentil, which doesn't list any preservatives in the ingredients and seems to list only real food, including cream and butter. Label is here. It doesn't need to be refrigerated and, honestly, it's pretty tasty.

Here's another one I enjoy by Kitchens of India of chickpea curry. Just like the one above, it comes in a silver pouch.

• Another example, this time non-Indian food in a non-pouch, is this box of soup by Pacific Foods.

Here's my question: How is it that this food doesn't need to be refrigerated? Is it something about the pouch or box they use? Is it the ingredients they use? Is there a preservative in here I don't know about? I generally try to avoid packaged foods that have strange chemicals in them and I eat organic when I can, but I am on a diet and these are easy, fast, low-calorie meals.

So can I feel ok with eating these? I always look at ingredients on everything I buy and, for instance, I won't eat foods with "TBHQ," "sodium benzoate," anything "dioxide" and stuff like that. Shelf-stable pre-made foods freak me out though; I usually go for fresh refrigerated foods or frozen foods when opting for pre-prepared food. But the convenience of these pouches is hard to beat. I do make my own food fresh too, but I don't always have the time or planning for it.
posted by AppleTurnover to Food & Drink (14 answers total) 1 user marked this as a favorite
I am assuming they're vacuum-sealed containers - not much will grow without oxygen, and properly clean prep will take care of the things that will (like botulism). Also, salt and sugar are both preservatives, and all of those dishes are going to have a ton of salt in them.

(I was just at a friend's house learning to can tomatoes, and she was telling me that there have been some issues with people coming to canning for the first time and wanting low-salt, low-sugar, totally natural recipes. There... aren't any. They don't work, because salt and/or sugar are necessary for the preservation process.)
posted by restless_nomad at 1:22 PM on August 27, 2017 [13 favorites]

Food goes bad because something eats it and you see the waste products or whatever was eating it. If you vacuum pack dried food in aseptic packaging then there's nothing there to eat the food and no oxygen for respiration (which most things need to eat food) if something gets in there that does want to eat the food.

Refrigeration drastically slows down the metabolic activity of things that want to eat your food and freezing usually stops it altogether. It's just another way of keeping the food pristine and uneaten. Salt and nitrites kills the things that want to eat your food by drawing water out of them. That keeps the food good for longer. Pickling? Vinegar kills off the bacteria and inhibs growth. Preserves, jam and jelly? Sugar does the whole osmotic thing to draw water out of bacteria and inhibit their growth.
posted by Talez at 1:23 PM on August 27, 2017 [6 favorites]

-Totally sealed packaging
-No air
-Heated to sterilize the contents
More info on retort packages.

These are perfectly ok to eat.
posted by phunniemee at 1:27 PM on August 27, 2017 [6 favorites]

This is the same principle as canning; it's just lighter and more convenient packaging.
posted by librarina at 1:28 PM on August 27, 2017 [6 favorites]

Looks like other folks have it. One additional note, I believe food in that type of packaging is pasteurized using high pressure - the process is know as HPP.
posted by phil at 1:32 PM on August 27, 2017 [2 favorites]

salt and/or sugar are necessary for the preservation process
Sugar is used in preservative amounts in jams and jellies but tomatoes and pickles use acidity.
I am canning tomatoes this minute using approved* methods and there is no salt but there
is extra lemon juice because modern tomatoes are less acid than old ones.
*Ball canning book
posted by Botanizer at 1:53 PM on August 27, 2017 [7 favorites]

Yup, this is basically canning but in a lighter-weight package. It's totally sealed and the contents have been thoroughly sterilized, so the shelf life is based on either the expected service life of the packaging, or the time it will take for internal chemical reactions between the ingredients to cause the food to become less palatable. Note that "less palatable" can be something like a change in color or texture, it definitely doesn't mean that it would necessarily be dangerous to eat at that point.

Nothing gets in, nothing gets out.
posted by Anticipation Of A New Lover's Arrival, The at 2:03 PM on August 27, 2017 [3 favorites]

Cool. In that case, I am going to order a ton of pouches from Kitchens of India off Amazon now! Nom nom nom. Thanks!
posted by AppleTurnover at 2:49 PM on August 27, 2017 [4 favorites]

If you have the time, this 99% Invisible Podcast episode describes how innovations in packaged food can come from military research and development. Retort packaging was driven by the Pentagon's need for longer shelf stability of rations.
posted by JoeZydeco at 3:42 PM on August 27, 2017 [5 favorites]

Yeah packaging is so high tech and good in the modern world that those little Indian curry packets are cheap and delicious and safe and reliable -- enjoy!
posted by SaltySalticid at 4:33 PM on August 27, 2017 [1 favorite]

Just heed the warning from the side of the box not to eat any packages that are bulging. That means that something went bad in the sterilization process, and whatever is living in the food is producing a gas, but that's really no different than the pop top on a jar.
posted by hwyengr at 5:42 PM on August 27, 2017 [3 favorites]

minor followup to JoeZydeco's point -- I discovered Tasty Bite when looking for vegetarian MREs for disaster planning. That shipment did not have attractive pictures on the box.
posted by clew at 12:45 PM on August 28, 2017

I love the Tasty Bites vegetarian packages but beware, they are super high sodium.
posted by vivzan at 6:20 AM on August 29, 2017

I've tried Tasty Bite and, it was a long time ago, but I didn't really like it. Kitchens of India and Trader Joe's hit the spot for me. All of these things do have pretty high sodium across the board so it's something I will keep an eye on with regards to the rest of my diet. I track everything I eat on MyFitnessPal so I can monitor that, at least.
posted by AppleTurnover at 12:17 PM on August 29, 2017

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