EXPERIENCED ICE CREAM MAKERS - CHEMISTS - ??? re: 2% MILK and MAKING ICE CREAM
I'm making fresh goat cheese ice cream, recipe from The Perfect Scoop by David Lebovitz.
Using Reduced Fat Organic Milk from the farmer's market (37% less fat than whole milk; homogenized and lightly pasteurized from a local dairy) I put together the milk and sugar in a sauce pan, and a pinch of salt. (The salt was NOT called for in the recipe.)
The milk separated when it got a little steamy! I wisked it back together and carried on (it didn't totally come together, clearly a suspension) and it's chilling now...any thoughts on what made that happen? The milk was a few days old but not soured - I tasted it before I heated it. I've noticed ready to go off milk separates in coffee, so I'm wondering about that. The lower fat content? The salt? Something weird in the mix of organic cane sugar and plain white cane sugar I used (only because I didn't have much sugar in the house, not enough of either type.)
I've tasted the custard, it's kinda great, tastes like good cheesecake. The heated milk and sugar is whisked into the egg yolks, put back on the heat to custard stage, and sieved over crumbled fresh goat cheese. Custard melts the fresh cheese, and blended together over an ice bath, cooling now to go in the ice cream maker.
First, I am not much of a chemist, nor am I an expert ice cream maker though I have taken some chmistry classes and made some ice cream but never with less than whole milk.
i don't think it is either the sugar or the salt - I think it is the reduced fat content of the milk. Homogenized milk means the milk has been processed to break up the fat molecules to tinier bits so that it does not separate so easily from the water; it makes the milk into an emulsion. I would imagine that as there is less fat total in reduced fat milk, the emulsion, which is probably more of a suspension, is necessarily less "stable" due to the altered fat/water ratio, and therefore more prone to separating. Also possible that heat exacerbates that tendency. Again, though, I'm no expert.
I too have also observed that milk which is nearly part its prime will separate when added to my tea so that is another possibility. Not sure of any details on that, though.