Reading this question: Emulsifier: is it safe to cook mayonnaise?

Is anything made less safe by cooking? (I'm not asking if cooking makes something worse-tasting, have bad texture, is culturally or religiously taboo, etc. just from a food safety perspective).

Please interpret cooking as loosely as you'd like. I would probably define cooking as "applying heat to raw food", but considering techniques like curing/pickling or freeze-drying, I'd be curious about those as well. What I'm not too curious about is failing to "cook" something adequately (not enough heat, time, salt, etc.), since the consequences of that are more straightforward.


3 Answers 3


There are a few cases were a closer look is warranted and which may be seen as "less safe after cooking":

  1. Yes, if reduced shelf life counts as less safe. If you take dried food - anything that has a nearly unlimited shelf life - and (re-)hydrate it, the shelf life goes down to mere days. The same goes for fruit and vegetables (from often weeks or even months, e. g. pumpkins, down to days).

  2. If your definition of "cooking" doesn't require a heating step, food preparation can cause cross-contamination when germs from the outside/surface are transferred to the formerly safe inside. Example: cutting fruit that wasn't washed well enough.

  3. A third case of "less safe" would be "cooking" with insufficient heat: there is a fine line between "kills pathogens over time" and "creates a cozy environment where pathogens thrive and multiply happily". Note that this is discussed in detail in our generic posts on the topic.

  4. A border case in a "food safety" discussion would be creating byproducts that might have negative long-term effects like acrylamide or residue from char grilling. But that's pretty much a grey area with a lot of uncertainties in the equation. (And we don't discuss health here on the site partly because of that.)

In short, if cooking for you includes "bacteria-killing heat" and eating reasonably quickly after cooking and ignoring byproducts then no, cooking does not make food less safe. Within these parameters we typically use the cooking process to make food safer.

  • Would "some non-homogenous ingredient could be dehydrated/melted, and thus hardened enough to cause injury - eg broken teeth, or something sharp and not water soluble inside you" be a valid food safety issue? Nov 12, 2017 at 23:18

Cooking apples or cherries with the seeds can extract the cyanide precursor (amygdalin) into the fruit pulp.

  • 1
    That was one of the examples I thought about, but wasn't sure if it is really the case. Sure, the seeds contain the amygdalin, but does it really get into the pulp after cooking? Also, people eat amygdalin now and then, what circumstances are needed for it to exceed safe limits in this case?
    – rumtscho
    Aug 24, 2017 at 14:17

Cooking mostly makes food safer to consume. However, canning is a classic example of how "cooking" food can go wrong. That is why there are strict guidelines around the process.

Let's say you take some raw fruit, rich in sugar, wild yeasts and lactobacillus. Oh, and some naturally occurring botulism and ecoli for good measure. Let's say you macerate this fruit and place it in a couple of different jars.

Jar 1, raw: This jar gets capped and put in the fridge overnight. You have toast with preserves the next day and paint the walls brown because you didn't kill the ecoli by cooking it.

Jar 2, raw but fermented: This jar gets capped and placed in a warm window where over many months it ferments into a tart, alcoholic beverage. The sugar content, alcohol and acidity have effectively preserved the fruit and killed the small amount of botulism and ecoli present, making it safe to consume (note that fermentation has it's risks too, but that's not the point here).

Jar 3, "cooked" / canned: This jar gets capped and placed in a boiling water bath for 15 minutes. From the perspective of immediate consumption, the ecoli is dead and the botulism hasn't been given enough time to form toxin. You eat this on toast two days later, and everybody is happy. Now let's imagine that you left this jar unopened on the shelf for two years. Your fruit preserves were not cooked long/hot/acidic enough to prevent the botulism spores from growing and forming botulism toxin. Now you have toast with jam and within a day you are laying paralyzed on the kitchen floor.

  • I'm confused... jar 1 doesn't seem to involve any "cooking" (assuming that "cooking" means "heating). You would have had the same exact result (painting the walls brown) if you'd eaten the fruit in hand rather than mascerating it.
    – Catija
    Aug 23, 2017 at 21:36
  • Right, jar 1 is the reference sample. It is supposed to be raw. Given that diarrhea is the baseline, the idea is to demonstrate that proper preparation (both raw and cooked) could prevent such, or an improper cooked preparation could be much worse (lethal).
    – Derpy
    Aug 24, 2017 at 2:59
  • Downvoted, because it is both not answering the question and contains some dangerous misunderstandings. The raw fruit has contamination which is either below or above the safety limits. If it is below the limit, you can eat from Jar 1 and 2, no problem. In this case, the food was safe and stays safe after cooking, and in jar 3, it is still safe after cooking, it is the improper storage (you created food with a shelf life of 3 days and stored it for 2 years) that caused the problem. If it is above the limit from the beginning, then it is not the cooking that turned it unsafe, it was (cont.)
    – rumtscho
    Aug 24, 2017 at 13:45
  • (cont.) unsafe to begin with. So not answering the question. And in case it was above the limit, fermentation won't make it safe, so your description that Jar 1 will make you sick but Jar 2 will not is dangeroulsy wrong.
    – rumtscho
    Aug 24, 2017 at 13:47
  • 1
    I think the intent is: A faulty canning process could conceivably make the result less safe than its raw state. Conceivably possible, since you are going through temperature zones that accelerate spoilage, AND because there is an assumption of non-perishability with a preserve that isn't there with a raw mixture... Nov 12, 2017 at 23:16

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