This topic is relevant to the Nacho Cheese recipe, but it has applications outside of it, which is why I'm mentioning it here in the forums.
I've made the Nacho Cheese recipe successfully quite a few times (without the SHMP), but I've run into difficulties now that I've tried to substitute parmesan cheese for cheddar cheese. Basically the sauce is way too thick with the proportions given (1:1 cheese and milk, 4% of cheese weight Sodium Citrate). I expect that this has something to do with a combination of issues: differences in viscosity at different temperatures, perhaps % water in each cheese, etc. I'm wondering whether anyone has some suggestions for making these sorts of cheese sauces out of cheeses other than cheddar. Are there standard changes in liquid (milk, in this case) for different cheeses? Do some cheese require different amounts/combinations of melting salts? Do some cheeses need to be melted at a higher temperature in order for the salts to 'activate'?