eli5: Why are the cans of canned vegetables or fruit always filled up with water or juice?

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I don’t see why e.g. canned green beans or peas couldn’t just be packaged as they are. Is it a food safety thing? Because it adds a lot of weight to each can…

(I hope the flair fits… I wasn’t sure where to put it as I’m not sure if it’s a biological or an engineering problem.)

In: Engineering
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You can’t can “air”. The can has to be full, of something that doesn’t get smaller when it cools from canning temperature to room temperature.

The liquid usually has preservatives in it that keep the food from spoiling. Without it, canned goods would have a very short shelf life.

1) the liquid prevents the stuff inside from getting bashed up

2) syrup add sweetness and preserves

3) it helps maintain pressure in the can so it does not crumple or burst.

1. Liquids are much better at heat distribution than gases. When you pasteurize the can, you won’t get green beans with crispy outsides and raw insides.
2. At the same time, liquids act as a heat buffer that allows cooking without moisture loss or caramelization through Maillard reaction. In short, it keeps most of the food properties.
3. It allows to add preservatives and flavorings in a solution.
4. Water is mostly uncompressible, so it makes cans much stronger. Try squishing a full soda can and then try when it’s empty…
5. Weight is not a issue compared to volume. What matters in transportation and distribution is the amount of cans you can fit in a box and the amount of boxes you can fit in a container.
6. Tied to the previous point, manufacturers are selling you cheap syrup, or brine at fruit or vegetable prices. Even after you drain the liquid, the items retain a lot of it. Just look at your juicy plump pear halves.