I've read from multiple sources that rennet used to be one of the ingredients in making skyr but it's not used anymore outside of traditional recipes. I do understand that acid + heat causes milk to curd and indeed, when I heated up a skyr I thought didn't develop to reuse the milk it did separate because of the lactic acid. But heating the milk with bacteria inside will kill the live cultures, so surely this is not how skyr is supposed to set.
The recipe I followed (and others I read to compare) insisted that heating milk to 95C and keeping that temperature for 10 min is required for the skyr to set later after I add the bacteria. It also advised to heat the milk very slowly, 1L of milk for over an hour and let it cool slowly, without an ice bath.
My question is mostly about this: is it possible that the way in which I heat and cool the milk before mixing in live cultures can influence if the curds will separate or not? And if it does, then why does this happen?
Here is the recipe I followed: https://icelandmag.is/article/make-your-own-skyr.