Why does my mozzarella crumble? I'm trying to make mozzarella at home. I'm following this recipe (without citric acid), but I also tried this one (with citric acid), without any result. I think my italian is sufficient for understanding the above recipes. I'll summarize the video recipe for you:


I took 2l milk, (exact type below) and heated to 40°C
Add 1tsp natural yoghurt for each liter of milk (I doubled this)
Add the rennet dissolved in cold water (exact type below)
wait 1h, cut up the curd (so far seems to be ok)
wait 20min, till the curd and the whey separates (bit suspicious: the curd does not sink)
break the curd into small ("piccoli-piccoli") pieces, and let them separate for 4 hours (very suspicious: does not sink, floats on top of the whey)
remove whey, put the curd into a sieve, and let it drip-dry for 18 hours (suspicious: when it seems dry, I put it onto a plate for the remaining time c.a. 4h?, but the plate fills up with whey)
now I should be able to form the cheese in warm/hot water, but I do not get to this point, because the curd/cheese falls apart, it stays in little crumbs, like cottage cheese


What am I doing wrong? The materials I use:


milk: 3.5% fat, pasteurized (not UHT or ESL) and homogenized
rennet: c.a. 0.5ml for the 2l milk


I'm planning to try to get natural milk, only cooled, no pasteurization and homogenization, but before I do that, I'd like to know, what went wrong.



Note: I've looked around here before placing the question, I found these:


this does not apply, because the milk I'm using is not UHT pasteurized 
the other questions are mainly about microwave recipes, which I try to avoid
It's a bad recipe.  Here's why:

The way to make mozzarella without using citric acid is to use cheese cultures to acidify the curd, since in order to achieve the cheese's characteristic stretchiness it needs to have a pH of between 5.0 and 5.6..

That recipe has you add a "culture":


  Add 1tsp natural yoghurt for each liter of milk (I doubled this)


... however, yogurt is not the same as Thermophilic cheese culture, which is what you use in mozzarella recipes. In fact, the 40C temperature you used is enough to kill the yogurt culture, meaning that it likely didn't acidify the milk at all. Besides which, the yogurt culture would have had other, undesirable, effects on the texture of the curd.

There's lots of other weird and suspicious factors in that recipe (18 hour drain?  WTH?); I'd recommend simply discarding it and using the Ricki Carroll recipe instead.