I'm not sure if this or this questions' answers satisfactorily cover my question but I am seeing a lot of answers that talk about the shelf-life of coffee and say things just "change" when adding sugar or dairy.

I make about 20oz. of coffee each morning and put it in a thermos. I then add my creamer to this at home and take it to work. Most days I get through it within a couple hours of being there, but some days I don't go through the whole container and the coffee is still pretty hot by the time I get home (go thermos!). I understand that if it was plain this should be fine, but does the dairy creamer break down over the day to the point I shouldn't be consuming it by the time I get home (about 9 hours after brew time) given it has been kept pretty hot most of the day ?

If I should be tossing this sooner by a certain time when is that? Does keeping it hot prolong life beyond the 2-4 hours in the danger zone I am seeing on other posts?

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    My personal inclination would be that if it's still hot when you get home, and it tastes normal, it's probably reasonably safe. I don't know what the official answer would be, though (and I tend to drink my coffee black). – user5561 Jan 14 '14 at 1:33
  • I've definitely had some after that 9 hour mark in the past and it seemed ok. I am generally more than willing to eat/drink anything that doesn't make me spit it back up, but as I continue on through my 20s I feel I should start being a bit more responsible. – Matt N. Jan 14 '14 at 14:44

The clock on the danger zone starts when the food temperature drops below 60 celsius. It should be 4 hours for coffee - two hours are for meat, where it is assumed that bacteria in it have had some chance to grow while it was being butchered, transported, and stored in a supermarket. In coffee and creamer, there will be no bacteria growth at all in the ingredients, it will start after you have brewed the drink and mixed in the creamer, and the temperature has fallen below 60.

If you want to go by the book, measure the temperature of the coffee inside the thermos 5 hours after brewing. If it is above 60 Celsius, then it is still safe up to 9 hours after brewing. Do it on several days to have a significant result.


The thing about dairy is that it comes with a huge bacterial load, but it's all stuff that's relatively benign to humans (assuming it was originally pasteurized). When it goes bad it gets chunky or stinky or both, and that's usually gross (sour cream, yoghurt, buttermilk, etc, being the exceptions), but not terribly harmful.

That naturally occurring bacteria also does a good job of suppressing the growth of other, more hostile, bacteria. It just out-competes it. Nearly all dairy products are based on this. Cheese, yoghurt, sour cream...they would be impossible to eat safely if it were not true.

All that being the case, I'd say that as long as your beverage still tastes and smells good, it's not going to hurt you: the bacteria that's going to blow up first will definitely change the flavour. My original answer to that first question was based more on long term storage.

The whole "Danger Zone" thing is based around uncertainty over your bacterial contamination. After a couple of hours warm, something will have established a sizable colony. In this case, it's probably going to be streptococcus lacti, and it's not bad for you.

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    The OP said "creamer". In my experience, this word is not used for pasteurized milk from a carton, but for powdered dairy products, or condensed milk, or UHT cream in single-use packages, and for non-dairy fat-based powders. None of these comes with the benign culture load capable of outgrowing the baddies. – rumtscho Jan 14 '14 at 14:44
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    And actually, even pasteurized milk is a hit and miss when it comes to different lactobacilii, depending on the pasteurization process. If the original flora was killed during the pasteuization, you can have recolonization by many different species. Your logic is generally applicable to raw milk, not to the products widely available today. – rumtscho Jan 14 '14 at 14:46
  • I had originally had pre-dairy'd in the question title and have changed it to be more clear. – Matt N. Jan 15 '14 at 18:43

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