.barrett: typically the freezing facilities are very close to the place where the vegetable is grown. so within hours, that vegetable is frozen. .it's not clear how well they'll stack up against current migraine therapies, because head-to-head studies haven't been done. . march 2012 (23) .allison aubrey, byline: like a lot of us, olivia mitchell (ph) has had some preconceived notions about frozen food. she prefers to buy fresh produce.