[Piotrsko]

Key point is method of recarbonization. Technically, my homemade is boiled sterile and I put it in the fermenter above 90 C then add hops. Next morning with the temp still about 27C I add the yeast then monitor it for a week or so. I still have active yeast but no method for injection of gas, so I add a couple ounces of sugar to the batch and bottle. Let sit for a week, viola, fizz. If the bottle doesn't explode, it's pretty much sterile (yeast excepted). I have a couple of bottles aging for a year so far. Lots of things for microbiology to eat in a beer bottle and they outgass like yeast. The term for this is a Gorse beer which is sour from the microbiology.

Manufacturers may or may not reheat, but they also add carbonation just before sealing the container so theoretically they could cook their beer all they want and even can it hot... it does taste different.