Cultured mozzarella vs citric acid(fast) mozzarella
On YouTube, fast or 30 minute mozzarella seems to be the craze. Stuff only works 1 out of 5 times. The flops do not make it to YouTube ;-)
So why the difficulty and inconsistency?
Mozzarella being quite a bland cheese, we need only acid and heat to plasticize the curd. Therefore artificial acidification seems a viable option, since we do not need much flavor formation from the cultures added. Enter citric acid(or any other acid for that matter), where we add some, reach the stretching pH and do just that. The fast method is very harsh on the proteins in the milk. We do not know the current pH of the milk when starting, so some days you add too little, some days too much, and on the odd occasion just enough. With cow milk we need to stretch in the range of 5.6-5.7 with added acid and with culture we aim for 5-5.3 in most cases.
When using cultures we get a slower and more controllable process that is biologically regulated. So when you make wine, the yeast stops itself at about 13% alcohol, same in the milk with acid formation to some extent. So instead of having an instant flop or success, we have regulation built into the process, so that we can test the curd in some hot water every 20 minutes or so , for stretch.
In this way we can be more sure of success every time we make mozzarella. So although you are waiting a bit longer, it is still a very low-labor cheese that is ready to enjoy, immediately.