I also cook

When tension mounts, and the outcome of an activity may not be what has been desired, Americans say "the cheese is getting binding". While the notion of the digestive effects of eating too much cheese is curious, it would be interesting to find how this particular expression got started...........

When you grate cheese and melt it in, you want it evenly distributed through the mix - with Mozzarella in particular, even if you put it in grated or in small chucks, if you are careless it can all come together in a lump - bound up. I think that the expression is about that phenomenon.