Let’s say you hard boil an egg, disinfect a container, and put the egg in immediately after boiling (still in shell).
Several days later the egg will go bad, but why? Haven’t you already murdered the eggs microbes by boiling it, and the container’s microbes by disinfecting it?
Where does the bacteria or fungi come from to spoil the egg?
In: Biology
if the jar was not properly sterilized and sealed, bacteria can linger and eat the jar’s contents, causing spoiling and mold. proper prevention of spoilage includes sterilizing correctly and completely, and canning with a good seal.
The world is full of bacteria and fungi. No matter how good and how quick you are at cleaning it and moving it to a sterile place, some bacteria and fungi will get in and grow. The only way to do it is to seal it in a container, and then heat it up to kill the bugs. That’s what we do with canning stuff – put the food in a can, seal it, then heat it up to kill everything inside.
The second thing is that some bacteria and fungi form robust spores. These spores can survive quite high temperatures, then revive later. It’s why most mass produced roods are acidic, salty or very sweet – they can’t heat up the food high enough to kill the spores without destroying the food, but as long as conditions aren’t favourable – acid, salt or not enough water – they spores don’t revive and don’t spoil the food.
Disinfection has to happen after sealing, or in a totally sterile environment, or the tiny amount of bacteria or fungi that make it into the jar or onto the egg between when it’s heated and when it’s sealed will grow out of control in a closed environment with plenty of food and no danger to the bacteria.
Generally, canned and preserved food is also stored in a medium that’s naturally hostile to bacteria and fungi, like a brine or a syrup instead of plain water. Without that hostile environment, you run into the same issue where a tiny bit of bacteria that survived sterilization can grow and multiply undisturbed.
You have to disinfect it after it’s sealed – otherwise bacteria from your hands or the air will recontaminate the egg after cooking.
There are also some compounds in food that are unstable. Proteins may break down over days or weeks. While usually this won’t make food inedible, it may lead to undesirable colors, tastes, and textures.
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