# How long does a freezer keep food good? **URL:** \ **Category:** Factual Questions\ **Created:** [November 10, 2008, 5:01pm UTC](https://boards.straightdope.com/t/how-long-does-a-freezer-keep-food-good/472054 "2008-11-10T17:01:11Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![SeanArenas](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeanArenas](https://boards.straightdope.com/u/SeanArenas)\ **Post date:** [November 12, 2008, 3:52pm UTC](https://boards.straightdope.com/t/how-long-does-a-freezer-keep-food-good/472054/21 "2008-11-12T15:52:50Z")
> [@masterofnone](#): > > If it’s the one in the picture, it does have a memory function - it displays max/min. > > Every auto-defrost freezer I’ve ever put a data logger in goes well above zero briefly twice a day. I don’t know what \*\*Snnipe 70E \*\*is talking about, but it may be specific to Sub Zero brand. Where can I get a data logger? How far over 0, and for how long? Do they get to 20 degrees over 0? > [@masterofnone](#): > > Note that this temperature spike will not show up if you suberge your thermometer in oil or alcohol, as that is to simulate what is actually happening to the food, instead of the air in your freezer. If you get a thermometer like the one in your link, it will display the air temperature. Unfortunately, this will only display the maximum temperature, and not the time at that temperature, so it won’t tell you if the defrost is staying on too long unless you time it just right. So even if the air temperature does get to 20 degrees over 0, as long as the temperature gets down below 0 again quickly, it’s not bad for the food and won’t cause huge quantities of frost on the inside of the package? I ordered that thermometer in the previous post, and can tape a piece of paper to the fridge, and write down temperatures and times manually several times through the day to create my own log sheet. Is the thermometer going to impress the service guy? The last service guy repeatedly ragged on the thermometer we currently have in the fridge. ---
**Author:** ![masterofnone](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@masterofnone](https://boards.straightdope.com/u/masterofnone)\ **Post date:** [November 12, 2008, 4:30pm UTC](https://boards.straightdope.com/t/how-long-does-a-freezer-keep-food-good/472054/22 "2008-11-12T16:30:21Z")
> [@SeanArenas](#): > > Where can I get a data logger? > How far over 0, and for how long? Do they get to 20 degrees over 0?. Here’s [one](http://www.dataloggerstore.com/p5567/lascar_el-usb-2.php), and substantially cheaper than I thought you could buy them for. What I usually see is the freezer bumping to almost 0C (32F) for a few minutes 2x a day, and holding -20C the rest of the time. > [@SeanArenas](#): > > So even if the air temperature does get to 20 degrees over 0, as long as the temperature gets down below 0 again quickly, it’s not bad for the food and won’t cause huge quantities of frost on the inside of the package?. Remember, food is almost always mostly water, therefore it has lots of thermal mass. It takes loads of heat to change the temperature of the food. Therefore, raising the temperature briefly will not thaw the food. The problem is that if the food is improperly wrapped, it will freezer burn, which is basically the same as freeze-drying. I have no idea if a short defrost cycle promotes frost inside the package, but that would indicate to me that moisture is being drawn out of the food. If the food is wrapped properly, this should not be a problem, as there should be little to no air space inside the packaging, and the packaging should be moisure resistant. > [@SeanArenas](#): > > I ordered that thermometer in the previous post, and can tape a piece of paper to the fridge, and write down temperatures and times manually several times through the day to create my own log sheet. That’s what I would do if I did not have access to a data logger - it’s a whole lot cheaper. > [@SeanArenas](#): > > Is the thermometer going to impress the service guy? The last service guy repeatedly ragged on the thermometer we currently have in the fridge. Probably not, but they generally don’t know what they’re talking about. If you want a thermometer that will impress some random store service guy, you’ll pay out the nose for one that’s NIST traceable. Or you can pay $25 for one like that in your link that’s made exactly the same way, but not certified. If you want a knowledgable service technician, look up refrigeration service companies in your yellow pages. Store service people are notoriously unreliable (I’m sure some of them are fine, but it’s a crapshoot). ---
**Author:** ![SeanArenas](https://avatars.discourse-cdn.com/v4/letter/s/df705f/32.png) [@SeanArenas](https://boards.straightdope.com/u/SeanArenas)\ **Post date:** [November 16, 2008, 2:10pm UTC](https://boards.straightdope.com/t/how-long-does-a-freezer-keep-food-good/472054/23 "2008-11-16T14:10:40Z")
OK, so we got that cool freezer/fridge thermometer which broadcasts the temperatures wirelessly to the LCD display. For the first couple of days, it’s helping us to adjust the temp inside the fridge and freezer. For instance, the fridge has apparently bee a little warm (about 45 instead of 33-40) so we can now adjust that and get a proper temperature there. Also, I was noticing that the freezer was staying between -10 and 0, so far so good. This morning I get up for a drink of water and notice that the freezer is at 20 degrees (positive)! So, I snapped pictures to prove it. [Thermometers showing +20F in freezer and +45F in fridge](http://picasaweb.google.com/cheeop/Temperature11162008#5269253800738449874) [The other thermometer we keep in the freezer](http://picasaweb.google.com/cheeop/Temperature11162008#5269253818092285506) (this should hopefully keep the next repair guy from telling us that 1 thermometer is not reliable!) [The position of the new thermometer sensor](http://picasaweb.google.com/cheeop/Temperature11162008#5269253836457894274) (the last repair guy told us our thermometer was positioned wrong, now we have them in 2 different places) [Settings of the fridge and freezer](http://picasaweb.google.com/cheeop/Temperature11162008#5269253808435569378) (note they are both set leaning on the Cold side) So, for a couple of days, the freezer temperature was within bounds, but this morning it’s in a definite bad range (20 over 0). As far as the “memory” function on this thermometer, it will tell me the highest temperature the fridge has reached, but not how long i spent at that temperature, which perhaps is the crucial information. According to masterofnone, it’s common for a fridge to reach +32F twice a day, for a few minutes. So if this is getting to +20F twice a day for (3 minutes? 5? 10?), that should be fine, but if it’s doing it for a long time, that’s not fine. Now, I opened the freezer to take a picture of the interior thermometer to see if it matches the digital one. A few moments after I opened it, I heard what what sounded like something turning on. Over the next 30 minutes, the LCD shows the temperature slowly dropping. Soon it was +10, then +5, now it’s -1. I’ve got to think that the temperature is spending quite some time over 0, however. This thermometer is not quick to change temperatures. masterofnone also suggested submerging the thermometer in a glass of oil so its temperature does not change when the freezer door is opened. But both the sensor I put in the fridge and the sensor I put in the freezer took a long time to reach their constant temperatures. Not just 5 or 10 minutes, more like 45 minutes. They also feel fairly weighty - I think they’re designed to work in this environment without constantly updating the temp every time the door is opened. In fact, the number on it doesn’t change after we open and close a door - the sensor must be deep inside the unit, not right on the edge, so the whole unit has to warm up or cool down for it to reflect a temperature change. So, that is what is disturbing about it displaying +20 at 5:00am. [Previous page](https://boards.straightdope.com/t/how-long-does-a-freezer-keep-food-good/472054.md?page=1)