First I have to say that in
no way am I much of a cheese maker. (Still, I was well thought of in the chicken yard
I believe that it may not be necessary to do anything at all and milk will form curds and the whey will separate. Adding vinegar or an active culture or rennet speeds up the process and makes it safer.
The value of the active culture is also apparently for the protection of the birds. I understand there are studies out there showing the culture has important benefits.
The dangers of just letting the milk sit there with no additives is that it will become contaminated with something toxic. Having the milk
about 70°F throughout the process is
important for it to work right.
Back when I had access to lots of milk here's what I did. And, not only were the hens appreciative but I think I was doing the right thing for them.
1. crush and dissolve 1/4 rennet tablet in a little water
2. pour a gallon of the room-temperature milk into a shallow pan
3. stir the water & rennet along with a little buttermilk into the milk
4. allow the milk to stand 12 hours or so until it is firm like a heavy yogurt
5. cut this into small pieces using a knife
6. allow to stand until it is one-half liquid and one-half curds
7. pour these curds & whey sloooowly thru a colander - the whey can go in the compost
Serve the curds to the hens.