Ice Cream Chemistry

[eeyore]

I am casein- as well as gluten-free, and so I occasionally make my own ice cream with a base of coconut milk, rice milk, and sugar. From there I've added chocolate, peppermint, and chocolate and peppermint.

What's funny about this is that the ice cream doesn't freeze (it will get thick), and instead gets full of bubbles. I like it this way, but I'm wondering why it won't freeze. I don't freeze the milks beforehand now, but I've done that before and it's frozen solid. I'm thinking that maybe it's the peppermint oil, because when I put that in it hasn't frozen. If it is the peppermint oil, could someone tell me why it keeps the ice cream from freezing?

[tarnalberry]

for something to "freeze" it has to become crystalline. fats don't easily do that. water does. the higher the fat content, the harder it's going to be to freeze it solidly. the more dispersed that fat is in the water (emulsified), the harder it's going to be to freeze solidly. air can do the same thing. if you can suspend air in the mixture while it is freezing, it's not going to freeze as solidly, as air will take the space between small ice crystals.

additionally, the freezing point of the substance makes a dramatic difference. alcohol has a very low freezing point. so mixing it in something will lower the freezing point of the whole thing. (most flavor oils are in a base of alcohol, for instance.) in the quantities your using, the alcohol is probably not as big a role, but that's just my supposition.

also, how are you making it? (what's your method?)

[eeyore]

I pour coconut milk and rice milk (in no particular amount) into a VitaMix, then add some sugar and whatever flavor I want, then I whir it until it's completely mixed and then I put it in the freezer in a plastic container. I usually make it around birthdays and times like that.

[tarnalberry]

having it *really* cold before mixing will help - 32F would be great (just before it freezes), if it's doable. if you can get yourself an icecream maker, that will help as well. eventually, it will freeze if your freezer is set cold enough, but it may take half a day or a full day.