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Sometimes I forget the potatoes in the oven when there's enough going on. And there they are again - baked last evening, they sat through the oven's cool-down and then through the night.

Should they be re-baked for safety? (That might just produce inedible potato-pucks.) Or is this a "cut your losses" situation?

Thanks!

Brendan
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1 Answers1

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You could probably leave a baked potato sitting at room temperature for days and it would still be safe to eat as long as it wasn't contained in a sealed container. But notice I said "probably." That's not the stance of food safety experts, and I would never serve other people something I'd left sitting at room temperature for so long.

Note that if you wrap your potatoes in foil to bake them, it's a different matter altogether. Thirty people in El Paso, Texas discovered this the hard way in 1994:

https://www.ncbi.nlm.nih.gov/pubmed/9652437

In April 1994, the largest outbreak of botulism in the United States since 1978 occurred in El Paso, Texas. Thirty persons were affected; 4 required mechanical ventilation. All ate food from a Greek restaurant. The attack rate among persons who ate a potato-based dip was 86% (19/22) compared with 6% (11/176) among persons who did not eat the dip (relative risk [RR] = 13.8; 95% confidence interval [CI], 7.6-25.1). The attack rate among persons who ate an eggplant-based dip was 67% (6/9) compared with 13% (241189) among persons who did not (RR = 5.2; 95% CI, 2.9-9.5). Botulism toxin type A was detected from patients and in both dips. Toxin formation resulted from holding aluminum foil-wrapped baked potatoes at room temperature, apparently for several days, before they were used in the dips. Consumers should be informed of the potential hazards caused by holding foil-wrapped potatoes at ambient temperatures after cooking.

Can you re-bake the potato to make it safe? The short answer is no, as explained by the accepted answer to this question. Although the botulinum toxin is destroyed by heating to 85C/185F for 5 minutes, there are other more hardy bacterial toxins that can't be destroyed short of turning the potato into a cinder.

The US Department of Agriculture, which tends to be ultra-conservative with food safety, has this to say about your potato:

https://www.stilltasty.com/fooditems/index/18081

How long can cooked potatoes be left at room temperature? Bacteria grow rapidly at temperatures between 40 °F and 140 °F; cooked potatoes should be discarded if left out for more than 2 hours at room temperature.

So when you get up in the morning and discover a potato in the oven, the only safe thing to do is toss it. Considering that a potato costs about 15 cents (US) in most of the world, why would you risk otherwise?

Carey Gregory
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    A wowwing great answer, @Carey-Gregory! Many thanks. – Brendan Aug 04 '19 at 00:50
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    @Brendan Thanks, and welcome to MedicalScience.SE. The usual procedure if you like an answer is to upvote it rather than post a comment. And after a few days if you think it answers what you asked and it's the best answer, you accept it. You can do both things by clicking the up/down arrow on the left if you like it, and the checkmark symbol if you accept the answer. – Carey Gregory Aug 04 '19 at 02:27
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    I will do so, @Carey! For now, when I tried up-voting last night, I received this message: "Thanks for the feedback! Votes cast by those with less than 15 reputation are recorded, but do not change the publicly displayed post score."

    My vote's recorded. But I'll see if it becomes public when I hit 15!

     – Brendan Aug 04 '19 at 11:03
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    @Brendan - If you accept the answer as correct you can accept the answer by clicking the tick underneath the voting buttons. That also gives the answerer and you reputation at the same time getting you to 15 rep more quickly. – Chris Rogers Aug 04 '19 at 11:11
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    One minor note: you lead with it being safe for days then end with toss after two hours. Which is it? Or did you mean unbaked for the first one? – JohnP Aug 04 '19 at 12:46
  • @JohnP I clarified that. The opening was personal opinion, the closing was official stance of food safety experts. – Carey Gregory Aug 04 '19 at 15:37
  • "Why risk it": "One cent is one cent, and food waste a global problem!" The USDA (can you cite a more direct src?) routinely underestimates solanoid toxins, yet gives guidance on not eating potato salad* in the summer, as before it's 'ready' it's already potentially spoiled? And oven baked if forgotten? The oven was just sterilized. How should microbes spoil it in 2hrs? Smell it, taste it. If they were edible before, peeled, these are good for 3 days minimum if stored below 18–15°C? Depending on moisture level and container. Your NCBI link has several days as well. 2 hrs needs better ref. – LаngLаngС Aug 05 '19 at 06:22
  • Kept in foil is 'bad', low acidity is needed and of course spores present. But it still took days. For "baked potatoes https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2672.2006.02987.x and generally: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2672.2006.02987.x 2hrs for "cooked" is still a head scratcher. Purely cooked, drained and left for >6 hrs at 30°C potatoes (if uncontaminated before and in reasonably clean environment) would not concern me the slightest now. – LаngLаngС Aug 05 '19 at 08:02
  • @LangLangC You're repeating largely what I said in my answer. 1) It would probably be safe to eat for days and 2) the USDA is ultra-conservative in their food safety recommendations. I think you'll find that they apply the 2-hour rule to virtually all foods. I think their reasoning in the case of cooked foods is that contamination sources may be unknown or unrecognized. – Carey Gregory Aug 05 '19 at 14:05
  • Partly true. My point is that USDA is indirectly sourced, the agency itself halfway crazy with these recommendations, and given the flow of argument, to me it reads as if this A tends to side with '2 hrs' ("Why risk"). And 2 hrs is not only on the "safe side, ultra-conservative", that's more like 'panicky unreasonableness'? The risk seems much higher for chaconine poisoning if eaten with skin straight out of the oven than from botulism eaten after 24 hrs (oxygenated) – LаngLаngС Aug 05 '19 at 15:31