Why does store-bought food last longer than homemade food?

A tin of soup and a pot of soup you made yourself are, chemically, doing very different things. The tin survived a factory process built specifically to make it survive: precise heat, an airtight seal, sometimes preservatives, sometimes very little water for anything alive to use. Your pot went through none of that. It is not that homemade food is somehow inferior — it is that store-bought shelf life is manufactured on purpose, and homemade shelf life is whatever happens when nobody engineered it.

Commercial food is built to survive time

Most packaged food that lasts a long time on a shelf, or lasts a surprisingly long time once opened, got there through a specific, deliberate process, not luck. Canned goods are heated well past a simmer, inside a sealed container, until the count of anything that could grow is driven close to zero — that is what "canning" actually means, and it is a stronger process than boiling a pot on your stove. Cured and smoked meats use salt, nitrites and moisture removal, all of which starve bacteria of what they need to multiply. Pickles and many condiments lean on acid and sugar, both hostile environments for the organisms that spoil food. Dried pasta, rice and crackers work by removing water almost entirely, since bacteria and mould need moisture to grow at all. None of this is a trick. It is the deliberate application of a handful of preservation methods — heat, salt, acid, sugar, drying — that people have used for centuries, now done with industrial precision and consistency.

The packaging is doing real work, not just holding the food

A vacuum-sealed pack of deli meat or a modified-atmosphere bag of salad is not neutral plastic. Removing the air, or replacing it with a different gas mix, slows down the specific spoilage organisms that need oxygen to thrive. That seal is also a barrier against everything that would otherwise land on the food after it is made: a hand, a spoon, the air in your kitchen, a cutting board that touched something else an hour earlier. A jar of pasta sauce stays sealed from the moment it leaves the factory until the moment you twist the lid. A pot of sauce you made tonight has been open, stirred, tasted with the same spoon twice, and exposed to your kitchen air the entire time it was cooling on the stove. The container is not incidental to the shelf life — for a lot of packaged food, it is most of the shelf life.

The cold chain that never breaks

Commercial refrigerated and frozen food generally travels through a cold chain designed never to have a gap: chilled at the factory, chilled in the truck, chilled in the store's case, chilled again the moment it lands in your fridge. Every link is monitored, because a single warm gap anywhere in that chain shortens the product's safe life, and the people running it know it. Your kitchen has no such discipline, and it is not supposed to — a pot of stew sits on the stove to cool, a container waits on the counter while you finish the washing up, leftovers get portioned onto a plate that then sits out during dinner. None of that is careless. It is just what cooking at home actually looks like, and it means home-cooked food usually picks up more time in warmer conditions than most commercial food ever does before either one reaches your fridge.

Comparing the wrong two things

The comparison that makes homemade food feel like it is failing is usually unfair on both sides: a shelf-stable jar of pickles against a bowl of stew you made last night. Fresh, unprocessed food is not actually the loser here — a store-bought rotisserie chicken, a fresh loaf from a bakery counter, or a ready meal from the chiller case behaves much closer to homemade cooking, and follows very similar rules: eat it within a few days, refrigerate it promptly, don't expect a shelf-stable timeline from something that was never processed to be shelf-stable. Homemade food is not a worse version of a jar of pickles. It is closer to a cousin of the fresh food in the chiller case, minus the industrial cold chain and the lab testing that gave that fresh chiller-case food its printed date in the first place.

What actually follows from this

The practical point is not that home cooking is risky. It is that homemade food never got the one thing a package gives you for free: a printed number backed by testing. Nobody ran a lab trial on Tuesday's curry. That is not a gap in your effort; it was never going to exist, because no one tested your specific pot on your specific stove. The only way to replace that missing number is the same trick that works for opened milk and any other unlabelled food in the fridge: supply the one fact a label would have given you, yourself.

• Write down when you made it. A date on the container, or in whatever you use to track the fridge, does the job the missing label can't.
• Cool it properly before that date starts to matter. Splitting a big pot into shallow containers so it cools quickly matters more than which day you eventually eat it.
• Treat it like the use-by category, not the best-before one. Homemade food doesn't reliably announce spoilage through smell or taste, the same way a lot of commercially dated fresh food doesn't — lean on time and temperature, not on sniffing it.
• Don't compare it to a jar on the shelf. Compare it to the freshest thing in your fridge, because that is the category it actually belongs to.

This is exactly the gap Munch is built around: a shared record of what is in the fridge and when it went in, so a pot of soup gets the same date-stamped, visible-to-everyone treatment as anything with a barcode — without anyone having to remember which Tuesday it was cooked.