Cold brew, room temperature, and safety

Coffee preparation techniques besides espresso like pourover.

#1: Post by dsc106 »

I've seen multiple things about cold brew being a potential food safety concern at room temp. Some advocate for the fridge for this reason, though I've always done room temp in the past and obviously many do.

But where is this coming from? Is this a concern at any point? Bottled store bought cold brew is supposedly not safe stored out of the fridge, according to the manufacturer? I've also heard some people mention botulism as a concern!

Not sure I understand the how/why of this. At what point would cold brew become unsafe, either for mild food poisoning or life threatening botulism, if left out of the fridge? Why?


#2: Post by Nate42 »

Two main things drive food spoilage: microorganism growth and oxidation. Both happen faster at room temperature than in the fridge. Having serious health effects is maybe a stretch, but it's bound to taste "off" after a while. I have noticed a sour flavor that starts to creep in after 4 or 5 days in the fridge. It's bound to happen faster at room temperature.


#3: Post by jpender »

I've kept small, sealed containers of black coffee at room temperature and after a couple of weeks they had mold on the surface. So while it might not be the best growth medium there is clearly a point where something visible grows. An open container would probably mold sooner. And before you see anything it wouldn't be surprising if something unseen were multiplying.

But is it unsafe? I don't know. Mold or bacteria isn't automatically harmful. There are plenty of delicious mold-ripened cheeses, for example. And numerous fermented foods that are often thought to be healthful.

I think I'll brew a fresh cup.


#4: Post by CathyWeeks »

Botulism is an anaerobic bacteria (i.e. it only multiplies or releases the toxin in the absence of oxygen). Unless you are *canning* your cold brew (which creates an O2-free environment), it is not a concern, though why you'd do that is beyond me, because canning it would involve heating it, and I think that would do unpleasant things to your cold-brew flavors. And where else in the process of making coldbrew at home are the conditions anaerobic?

What you have run into with the warnings you saw, is the fact that in general people rarely understand food-borne illnesses and are terrible at understanding risk. If you ever hang out on food preservation and canning forums, people get REALLY funny about it. You'll see stuff like: "What if I can XYZ in ABC manner?" and the answer is usually "OH MY GOD YOU ARE GOING TO DIE OF BOTULISM!!" The USDA has really strict guidelines (which should be followed!) and they only publish the times/pressures/canning variables once each recipe has been thoroughly tested. Testing means that the same recipe is made 100s or thousands of times and then canned and then tested for contaminants. But it's impossible to test each recipe (particularly for soups or other mixtures of foods), and if there are no guidelines, it means it hasn't been tested. It doesn't mean it's unsafe, just that it hasn't been tested. And untested does not automatically equal unsafe. It just means the risk is unknown. The reality is that one SHOULD follow safe and tested methods, but I do find people's attitudes a little ... over the top, I guess.

Many (most?) microorganisms that are present in our environment are relatively harmless, and many are actually beneficial. You can make hard cider by taking your pressed apple juice, covering it with cheesecloth to keep out the fruit flies, and letting it sit at room temp for a few weeks. Sour-dough starters are created the same way - you mix flour and water in a jar, cover it with a cloth, and every day you discard some of the mixture and add fresh. Wild yeasts and other microorganisms from the air do their thing and pretty soon it's bubbly and ready to leaven a bread. And here's a cool tidbit: San Francisco sourdough is famous because the conditions in the bay are just right for a particular strain (or strains) of particularly tasty microorganisms. If you take a sourdough starter from SF and move somewhere else, it will only taste like SF sourdough for a short time. Slowly your local microorganisms will replace the ones from SF and then it will eventually taste like all the local sourdoughs.

As others have said, there are cheeses that are deliberately exposed to yeasts and other microorganisms to give them the right flavor.

There are certainly some exceptions - you aren't supposed to use windfall apples to make juice or cider because being on the ground is more likely to introduce more dangerous pathogens, though when making hard cider, the beneficial yeasts out-compete the unwanted pathogens (sweet cider is another story, as there's no fermentation). There is no evidence of food poisoning ever occurring with hard cider. Still better to leave the windfalls for horses or compost.

And, what you are leaving at room temperature matters as well. Some things, like fresh meat butchered in unhygienic conditions (which is most meat these days) or pasteurized milk just make excellent growth medium, so don't leave those out at a room temp for long. Unpasteurized (raw) milk shouldn't be left out for long either unless you are deliberately souring it, or making butter (modern buttermilk is cultured with bacterias to produce lactic acid, but the old method was to let it sit at room temperature, covered, and the culture was introduced just from the air). Another tidbit: Raw milk sours in a pleasing way at room temp, while pasteurized milk just rots. But it's hard to find safe raw milk with our modern dairy farm techniques, so as much as I like it, I haven't had it in years (no source safe enough to suit me nearby).

Coffee beans - by the time they've gotten to you, have sometimes fermented (depending on the processing), then dried thoroughly, then roasted. The chances of there being any dangerous pathogens in the beans is pretty low. There is some worry about mycotoxins from improper storage, but studies show it's not a big risk: ... offee-myth

So ... make your coldbrew at room temperature if you want, then get it into the fridge promptly, and you should be fine. I usually get mine into the fridge within about 4-8 hours of starting the brewing (and once 24 hours), then it keeps in the fridge for a week or two. I do notice it starts to taste funny toward the end of the second week and I discard it. I once left it in the fridge for a month and did find blue spots of mold floating on the surface (where there's more O2 available). I dumped those. :lol:

Added: If you got this far - I recommend reading Wild Fermentation by Sandor Katz if you are interested in the topic.