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I made some cookies about four days ago - a modification of a fairly standard chocolate chip cookie recipe augmented with cocoa powder in the dry ingredients, and marshmallows in the center. They are moist at the center and crisp at the outside. Baked at 350 F for about 15 minutes.

They were left in my car, at a temperature of probably about 90 F (outside temps were cooler, and I was parked in the shade, but it was very hot out), for about two hours later that day. They've been in my refrigerator since then.

Now, ordinarily I wouldn't hesitate to leave them out on the counter (at a normal 70 F or so) or in the fridge, and eat them until they were gone, or became too stale. I confess, I didn't think twice about eating one this evening, either, until I read about food safety on here and saw the special rules about 90 F and higher temperatures.

My question is: Are foods that are normally considered safe for some days/weeks at 70 F unsafe after a shorter time 90 F? If so, does the standard "one hour at 90 F" rule apply, or is it some longer period of time? Is the added risk significant enough to be determinable?

Edit: In appreciation of the thorough answers, just want to update everyone: after more than a day, no ill effects. I've continued to eat them. Believe me, they are amazing cookies. If anything else happens, I'll update again, but otherwise, thanks for the responses and it looks like no harm, no foul! (Naturally, this is only anecdotal, but at least it's a nice data point.)

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Baked goods are generally considered to be a 'low risk' food when you're dealing with health codes. That is to say, you don't typically need to worry if they've been kept in the 'food danger zone' for too long on a period.

In fact, I'd say that some of the best cookies I've had in the past decade were chocolate chip cookies that had spent an hour or two in a hot car shortly before eating. (the chocolate was just to the point where it melted in your mouth as you ate it, without being so warm that it was melting all over your fingers).

So, is there increased risk? Yes, especially if they had been contaminated with something before being put in the car. But for breads and cookies, I wouldn't personally worry about a couple of hours at a warmer temperature.

I'd be more cautious with baked goods more hospitable to microbial growth -- wet pie fillings, meat pies, etc. Although pepperoni rolls are generally okay, as the pepperoni itself is something that's shelf stable for multiple weeks. (and they're really good when they're slightly warmed, like having been in a warm car)

If you wanted to be really paranoid about the whole situation, you could've put most of the cookies in the fridge, but have left out a couple at room temperature in a sealed container. This would serve like a petri dish to attempt to determine if there is significant microbial contamination to worry about. If they don't go all strange on you after a couple of days, the ones in the fridge should be fine to eat.

  • I'm not so sure about the test in the last paragraph where some of the cookies are left out. Food can be unsafe to eat long before it goes all strange. However, the rest of the answer is fantastic. Since cookies have lots of sugar and very little water, it's really unlikely that any dangerous microbes will grow in them. – mrog Jun 22 '18 at 23:28
  • @mrog : which is why I'm saying that the ones in the fridge should be okay, not the ones on the counter. As most microbial activity doubles for every 10°F increase in temperature, a 'room temperature' of 70 to 90°F should spoil 8 to 32 times faster than what's in the fridge. So if it doesn't show signs of spoiling after two days, what's in the fridge should be fine. But I'd only do this for low-risk foods, and mostly only because I was raised in a family where you didn't waste food. – Joe Jun 23 '18 at 4:05
  • Okay, that makes sense. I've never seen a spoiled cookie, though. They tend to just get stale. But, I suppose it could happen if there's enough water present. – mrog Jun 24 '18 at 4:58
  • @mrog : I've only seen it happen with a fairly moist cookie in a sealed container. (it was kinda fudgy ... more like a brownie than what I typically think of as a cookie). But I'd probably do the same test if I ever made maple bacon cookies again and ran into this situation. – Joe Jun 24 '18 at 20:52
  • Okay, I can see how that would happen with a fudgy cookie in a sealed container. I bet the cookies were really good before they went bad. :-) I don't usually make cookies with more moisture than a typical chewy chocolate chip cookie, and I live in a dry environment, so I'm not used to cookies going bad. – mrog Jun 25 '18 at 16:20
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One of the most important things to consider with regards to spoilage is "Water Activity"...Bacteria need water to be able to reproduce, and things (like cookies) that have very little water activity are very unfriendly to bacterial colonies.

I wouldn't worry about cookies. They'll go stale, but it's unlikely they'll grow any significant bacteria.

  • Interesting! How would the moist-ness of the cookie affect water activity? These are probably a "normal" level of moist, e. g. crispy on the outside and moist on the inside. Does that mean they'd be less safe than, for instance, a biscotti? – ivraatiems Jun 22 '18 at 17:40
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    @ivraatiems: Biscotti last forever...I'd think a moister cookie wouldn't last as long, but it'd still be safe for a good long while...Weeks. Lot of what makes them moist is fat, and fats last pretty well at room temp. – Satanicpuppy Jun 22 '18 at 18:58
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    That's an excellent answer. There's very little water in baked cookies. The abundant sugar helps a lot, too. It's unlikely that anything would grow in them, even after a few days. – mrog Jun 22 '18 at 23:25

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