Why would parsnips make a beef stock not freeze? I made a beef stock the way I always do, except that I added parnsips. Then I put the stock in the freezer and when I took it out, the stock was not frozen. It was freezing cold, but instead of having the consistency of ice as I would have expected, it was more like jelly. I think the only thing I did differently was adding the parsnips (although I suppose it's possible that the bones had an unusual amount of collagen for some reason).

Has anyone ever observed this effect from parsnips, or what else could be going on here?
I dont think that adding parnips to a beef stock would change the chemistry. I would give the beef stock a longer time to freeze as well as check the temperature in your freezer!