Can I use my milk temperature as a proxy for my fridge temperature?

June 23, 2018 11:32 AM

I think my refrigerator is not cold enough but I want to be sure. I don’t have a wireless thermometer, but I do have an instant-rest thermometer. If I sumberge the thermometer probe into the milk jug or a quart of yogurt or something similar, shouldn’t the temperature of the milk/yogurt be approximately the temperature of the refrigerator, assuming that the door has been closed for a number of hours, the milk/yogurt has been in there for several days, etc.? Cause the milk is 42 degrees, which strikes me as too warm. Thanks!
posted by griseus to Home & Garden (6 answers total)

Yeah, that logic seems sound to me. Things tend towards temperature equilibrium with the space they're in, and fridges cool things down from room temperature in hours rather than days or weeks. I'd say your biggest source of possible error would be how accurate your thermometer is and how correctly you're using it, not any temperature difference between the milk and the rest of the fridge.

(FWIW, the official guideline is that your fridge should be 40 or below, and I've seen the suggestion that you should really shoot for 35 so that if you're off by a few degrees you're still safe. So yes, that's a bit too warm.)
posted by nebulawindphone at 11:40 AM on June 23, 2018 [3 favorites]

To me, "cold enough" means cold enough to keep the milk from going bad, so this is exactly what I'd do. When I drink some milk and it's not cold enough, I turn the fridge down a little bit.
posted by 8603 at 12:14 PM on June 23, 2018

You could just leave the instant-read thermometer in the fridge. Periodically, open the fridge and turn on the thermometer. Should give you a good idea of the temperature inside the fridge.

The milk method would probably work, but it might mask fluctuations. If a gallon of milk is 42 degrees, does that mean that the fridge is a constant 42F? Or, could it mean that it swings between 32F and 50F?
posted by reeddavid at 12:56 PM on June 23, 2018 [2 favorites]

I'd go to a hardware store and invest in the cheapest standard wall thermometer, and tape it inside the fridge to the back wall. I doubt if you'll find a huge swing like 32 to 50, just a few degrees of flux at most, but as noted, ideally it should be in the 30s.
posted by beagle at 1:10 PM on June 23, 2018 [1 favorite]

In the wonderful world of biotech we'd target 39.2 (4°C). 42 is not significantly far from that though it could be a skosh lower.

The other thing we'd do - for routine monitoring we'd keep the thermometer (or temperature probe) in a bottle of liquid so that when you opened the door the warm air swirling around in there wouldn't throw the measurement off. We usually used glycerin, but only because it doesn't evaporate. Measuring the temperature of the milk should be fine.
posted by Kid Charlemagne at 8:19 PM on June 23, 2018 [2 favorites]

Echoing Kid Charlemagne.

As an intern in a lab for a few summers I had the job of checking all the thermometers in the fridges on a weekly rotation making sure that they were the correct number. Also as part of that job I had to calibrate the thermometers yearly with a (velvet box stored) NIST thermometer. We had special short thermometers that were kept in sample vials of glycerin. The glycerin was just to keep thermal mass around the thermometer and not cause artificial reading that were too high from the warm air blowing in when the door was opened. Your use of milk is essentially doing the same exact thing, except milk is tastier than glycerin, but will go off much easier.
posted by koolkat at 3:54 AM on June 25, 2018 [2 favorites]