I decided to get 100% Propylene glycol for my application. RV Antifreeze has a freeze point of 8F, but reports stated that freezes at a slightly higher. The MSDS for the RV Antifreeze states it as:
Propylene Glycol - 25-30%
Water - 64-70%
Glycerol - 4.0-5 mg/m3
DiPotassium Phosphate - 0.5-1%
I think the RV fluid work perfectly fine for your application, but so would 100% PG, which is probably a bit more food safe for incidental contact. Filling up a chest freezer takes at least 20-25 gallons, which is quite expensive. I would say get 100% Propylene glycol and then cut it yourself with water to get the temp range that you want.
WFF
Thx, where you getting you're PG from?