This seems a good point to bring up churning. The McGee recipe, obviously, didn’t call for it. Why not? Well, as you can gather from the below posts, ice cream makers and churns are all about motion: freezing a small amount of mix against a cold surface, scraping it off, and freezing some more. The McGee recipe, since it freezes the mix over a wide surface area relatively quickly, doesn’t need to be churned (just “kneaded” the one time). Yet the act of churning does something else to the ice cream mix: it incorporates air into the ice cream. This is important if only because air bubbles make up more of the miscellaneous whaddyacallem’s that prevent crystallization (see this morning’s post: “Freeze!”). Oftentimes the more air, the more scoopable the ice cream is. Thus most ice cream manufacturers add at least some air intentionally. There’s even a term for it: overrun. It’s popular to complain about overrun in ice cream circles, since the assumption is that by making consumers buy more air per tub, the manufacturers make more money. This may or may not be the case, though taste tests prove that, provided there’s not too much air in the ice cream (thus making it insubstantial), consumers find ice creams with at least a certain amount of “overrun” creamier. The “double churned” ice creams that are all the rage these days are case in point. Based on the name, people assume they’re richer than normal. In fact the reverse is usually true. The extra air bubbles allow the makers to take some of the fat out, thus delivering a creamier feel in the mouth with fewer calories.