# Refridgerate after opening...why? **URL:** \ **Category:** Factual Questions\ **Created:** [February 11, 2001, 8:37am UTC](https://boards.straightdope.com/t/refridgerate-after-opening-why/54026 "2001-02-11T08:37:31Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Heath\_Doolin](https://avatars.discourse-cdn.com/v4/letter/h/5f9b8f/32.png) [@Heath\_Doolin](https://boards.straightdope.com/u/Heath_Doolin)\ **Post date:** [February 11, 2001, 8:37am UTC](https://boards.straightdope.com/t/refridgerate-after-opening-why/54026/1 "2001-02-11T08:37:31Z")
I have found a few no refrigerated foods that ask us to fridge it after opening. Why? I figure its got something with the opening (hence…after opening. Smart man I is.) but why? Is it the preservatives (and I believe it mostly the heavily chemical stuff that asks this) or what? Is the air waiting for something like this to degrade it and the deep cold protect our dips from disappearing? WHY WHY WHY? ---
**Author:** ![Major\_Feelgud](https://avatars.discourse-cdn.com/v4/letter/m/3be4f8/32.png) [@Major\_Feelgud](https://boards.straightdope.com/u/Major_Feelgud)\ **Post date:** [February 11, 2001, 8:46am UTC](https://boards.straightdope.com/t/refridgerate-after-opening-why/54026/2 "2001-02-11T08:46:09Z")
You got to thank Pasteur for this. He demonstrated that there’s a lot of microscopic organisms in the air. Once you open that can or jar, bacteria and such land on it and start feasting. If you don’t refrigerate, then the food becomes a mass of bacterium that will make you sick. But that’s just nature’s way of recycling. If there weren’t any bacteria around dead stuff would lay around for ever. ---
**Author:** ![Heath\_Doolin](https://avatars.discourse-cdn.com/v4/letter/h/5f9b8f/32.png) [@Heath\_Doolin](https://boards.straightdope.com/u/Heath_Doolin)\ **Post date:** [February 11, 2001, 8:48am UTC](https://boards.straightdope.com/t/refridgerate-after-opening-why/54026/3 "2001-02-11T08:48:58Z")
dammit…I thought aging the mayo in the cupboard a few weeks would made it taste better ---
**Author:** ![Nimue](https://avatars.discourse-cdn.com/v4/letter/n/d26b3c/32.png) [@Nimue](https://boards.straightdope.com/u/Nimue)\ **Post date:** [February 11, 2001, 10:29am UTC](https://boards.straightdope.com/t/refridgerate-after-opening-why/54026/4 "2001-02-11T10:29:08Z")
It’s also worth noting that refrigeration doesn’t stop the bacteria; it just slows them down. Eventually stuff in the fridge will go off (at varying rates). ---
**Author:** ![schief2](https://avatars.discourse-cdn.com/v4/letter/s/cab0a1/32.png) [@schief2](https://boards.straightdope.com/u/schief2)\ **Post date:** [February 11, 2001, 7:12pm UTC](https://boards.straightdope.com/t/refridgerate-after-opening-why/54026/5 "2001-02-11T19:12:38Z")
> [@](#): > > \*Originally posted by Heath Doolin \* > \*\*dammit…I thought aging the mayo in the cupboard a few weeks would made it taste better \*\* Uh, actually, you _can_ age that mayo if you feel like; it’s just not going to improve the flavor any. Or so says [Ann Landers](http://www.thehollandsentinel.net/stories/092300/fea_40.html), anyway. Of course, she’s pretty well known around these parts for spreading ULs and other falsehoods in her column, but for once it looks like she actually did her homework: > [@](#): > > Dear Ann: {some blathering deleted}No one in my husband’s family refrigerates their jars of mayonnaise - even after the jars are opened. The mayonnaise is kept in the pantry until it is finished. Please be aware that we live in an area where the temperature outside can reach 107 degrees. What I can’t understand is why none of them ever get sick. Can it be that they are just lucky? My mother-in-law says her mother used to do it, so maybe the whole family has built up some kind of immunity. > > Do you have any idea why this is so? > > BAFFLED IN BAKERSFIELD, CALIF. > Your question intrigued me, so my office contacted the Association for Dressing and Sauces in Atlanta. Believe it or not, we were told commercial mayonnaise can be stored at room temperature (although temperatures of 107 degrees would be too hot). **The eggs are pasteurized, and the acidity content is high enough to kill most bacteria.** Refrigeration is recommended, however, to retain the container’s original flavor. Kraft Foods strongly recommends refrigerating mayonnaise after opening the jar to ensure good quality and to minimize the risk of contamination. (emphasis mine) Further confirmation, of sorts, comes from the Hellmann’s Best Foods FAQ, which remarkably, I’ve posted a link to before: > [@](#): > > Once opened, mayonnaise should be refrigerated to maintain its flavor. Notice the conspicuous absence of any warnings about disease or illness as a reason to keep your mayo in the fridge. (For some reason the Hellmann’s link looked really screwed up in preview, so here it is: [http://brands.bestfoods.com/hellmanns/faq.asp](http://brands.bestfoods.com/hellmanns/faq.asp) )