Came to think about this while eating a store bought chicken curry with rice meal. The packaging had a the expiration date on the 24th, if kept in the fridge. Meanwhile, had I stored leftovers of same food I’d have made myself, it would probably only last a few days in the fridge (especially rice, which is said to expire fast)
Hence I wonder, how do they get the food to last so long? I get it has to have something to do with better hygiene and airtight packaging, but that alone can’t make it last so much longer, right?
In: Biology
Sealed packaging does a lot of work. As in, a *huge* amount of work. Notice how many foods and sauces will have a ‘refrigerate after opening’ or ‘use within 7 days after opening’ on the label. Another part is industrial preservatives, but even without that you can achieve similar results just with proper household canning methods.
What makes most food spoil? The answer is mold (at least in our modern world of easy access to refrigeration; bacteria is usually a problem for more specific foods and/or temperatures, and pests are *much* less likely to be an issue inside a fridge).
Mold spores are *everywhere*, and the only reason they are not a constant problem to our health is that they just don’t grow well in our bodies (thanks, immune system!). But they *do* grow well in moist, lightly aerated situations, which is what most of our cooked leftovers are. Even when refrigerated, though slower than room temperature.
So industrial packaging will either use heat to kill most of the spores (canning/pasteurizing) or use alternate airs (such as nitrogen gas, a famous example being potato chip bags) before sealing the packaging for any of those ‘long shelf life’, read-to-eat foods. An alternative is having something else about the food making it hard for mold to grow (e.g. acid or salt), but I don’t think that’s the kind of food you are thinking of; these examples will usually have an expiration date that is months or years away, not just weeks.
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