1 hour ago, ccp900 said:Thanks jandreas I’m not sure why I missed your comment there.apologies
why is 6.9 chosen?
The basic idea is that in an unstabilized solution, you can have problems if the milk solids non-fat concentration is greater than 1 part in 7 parts water. This is a very loose approximation; there are many other factors. The water activity of other dissolved solids is one. Temperature is another. Solutions are more stable at lower temperatures, BUT ... because of fractional freezing, the concentration of msnf goes up and up and up the more hard-frozen the ice cream is. So the temperature relationship is completely non-linear.
Corvitto's formula is an even more vague approximation than the 1:7 rule, because there are sources of msnf besides milk powder (like, milk and cream). And because there are solids besides fat and sugar. So with his equation, in addition to using a rather rough general principle, you're just guessing at the quantities of both msnf and water.
But happily, the shortcut is very simple: if you use stabilizers, you shouldn't have to worry about any of this unless you're trying to do something extreme.
