Linuxboy's posts in another forum really helped me understand flocculation. Here's a practical explanation. Linuxboy can explain casein losing electrons.
1- Add rennet and start a timer.
2- Float a small bowl on top of your milk.
3- Spin the bowl. The bowl spins because the milk has NOT flocculated.
4- Let it sit for probably 8-10 minutes
5- Try to spin the bowl every 30 seconds or so
6- When the bowl won't spin, that's the flocculation time.
7- Every cheese has a multiplier from 2 to 6. There are references.
8- Floc Time x Multiplier = TOTAL time from rennet to curd cut.
Example - Parmesan might use a multiplier of 2.5
If the floc time is 10 minutes then 10 x 2.5 = 25 minutes
So the total time from adding rennet to cutting curds is 25 minutes
Use this time REGARDLESS of what the recipe says.
This takes the guess work out of rennet time to a "clean break". Compensates for changes in milk, rennet, starter activity, ripening temperature, pH, etc. The lower the multiplier, the drier the finished cheese because softer curds at cutting will give up more whey.