Cheese growing during overnight acidification?

[nightsky]

I used (frozen) raw milk for the first time yesterday to create a Pont-l'Eveque style cheese. All my previous cheeses were made with P/H milk and I've noticed that my previous cheeses would shrink in their forms while acidifying overnight (whey drainage?).

On the other hand, this raw milk cheese surprised me when I saw it this morning. It grew taller (maybe about 1/4 inch/5 mm taller)! My guess is that some culture in the milk is producing CO2 thus causing the expansion. Is this normal when dealing with raw milk or did mine get contaminated?

I'm not sure if this information matters but I rennetted at pH 6.45 and hooped it at pH 6.39 and after overnight acidification, it's at pH 5.1. Vat temperatures were maintained at 32C while draining temperatures were held at 22C.

[AnnDee]

Most likely too much clostridium thriving in it.

[nightsky]

From what I've read, Clostridium seems to be associated with late blowing while early blowing is from coliforms and yeasts. Since I renneted not too long after introducing my starter cultures (my milk pH was already low to begin with), perhaps they never took hold and got outcompeted with the native cultures in the milk. I'll probably keep the cheese as an experiment just to see how it looks like.