I have asked the following question before: Is it safe to only rinse visible residue from container if I then refrigerate the container?

I've gotten some great answers to it which help me further understand the variables at play here, but I stubbornly suspect a large part of their final conclusions was influenced by gut instinct, rather than genuine consideration of the scenario vs. other more traditional practices that are considered food safe.

(EDIT: I was wrong! It appears the defining factor here is the bacteria that would be introduced by eating - specifically the stuff in the saliva that would be transferred into the container via cutlery.)

I've then decided to ask a more specific, more rigorous question, which would hopefully help me decide whether I am wrong in this analysis, and if so, why. I propose two scenarios:

Scenario 1

Say I came up with a hypothetical monster recipe that included some scrambled eggs, pot roast, broccoli with cheese, steak, and black bean chilli. Then I took half of it, had a horrible time eating it, and left the rest in the fridge until the end of the night, when I reluctantly ate the rest.

(Wow, that wouldn't be a very good recipe! Yes, I agree.)

Scenario 2

Say the next day I decided that all that stuff would taste better separately, and prepared each meal individually throughout the day. I then ate each meal off the same dish, rinsing it afterward in a manner that would remove all visible residue from the dish.

For the purpose of the question, assume I rigorously measured the total sum (food+container) of time spent in the temperature danger zone, including transportation, preparation and storage, and taking into account time to cool down in the fridge etc, and it added up to exactly an hour and thirty minutes in both scenarios. I am aware it would be more difficult to perform such a calculation in Scenario 2.

I know Scenario 2 sounds more gross, but are there factors that make it worse from a food-safety perspective than Scenario 1? Would Scenario 1 be considered not food safe by government standards (due to cross contamination and mixing a lot of foods)? If not, why would Scenario 2 be any less safe? One could argue it would be even more safe, given that there is way less food in the container most of the time (a microscopic amount).

The only thing I can think of that would make it worse is the potential presence of saliva in a dish I've eaten in vs one I haven't, which would interact with the microscopic residue left on the dish - but I imagine the water would readily rinse away the spit.

  • Please let me know if asking a similar (but not the same) question is frowned upon. I imagined it wouldn't be fair to those who answered my previous question to change it to this one, and decided to ask a follow-up instead. Apr 7, 2021 at 20:21
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    Scenario 1: Depends on time the food spent in the danger zone before refrigeration, the mixing of food is not really relevant if it is all cooked. Scenario 2 is essentially the question you asked previously, isn't it?
    – moscafj
    Apr 7, 2021 at 20:43
  • Yes, scenario 2 is basically the same as before, except I've asked to consider the food was definitely not in the danger zone for 2 hours. The difference is that the new question directly compares the scenario to another that is considered food safe, and asks specifically for what factors would be different. Apr 7, 2021 at 20:53
  • I am a bit new to the site, so if anyone knows the reason why this question is being downvoted, please let me know! If it sounds like I'm trolling, the ridiculous propositions are designed to keep both scenarios as similar as possible (regarding cross contamination, time in danger zone etc.), so I can understand the underlying principles I should use to think about this. I swear it is a legitimate question! Apr 7, 2021 at 21:44

1 Answer 1


The answer is exactly what you speculated - the spit. Well, not the spit itself, but the microbial contaminants from your oral cavity that you are introducing to the food when you eat.

Your mouth (and rest of you too) contains a whole bunch of microorganisms (around 700 species in the mouth). Each time you put an eating implement in your mouth and return it to your plate, you are introducing some bacterial components that can multiply in the food residues. If you used your fingers to pick up some of the food or touch the plate at all, you introduced a different set of bacteria, which may be good or bad.

When you rinse a plate all you are doing is removing gross (see definition B) contamination. There is still microscopic contamination there, particularly oils and other non-water soluble components.

Bacteria in general are very small - most are around 0.5 - 5 micrometers (that's 1000ths of a millimeter or 0.00002 - 0.0002 inches). These are so small that no matter how well you rinse there will be some left on the surface of the plate you ate off and these can multiply in the presence of the food residues also left on the plate. How much they multiply depends on the temperature (that's why cold used for storage), nutrient source (how readily metabolizable they are) and which strain of which species they are.

When you ate the meal the night before, you introduced a bunch of bacteria. Every time you take the food out of the fridge and it reaches the "Danger zone" then the bacteria are multiplying. This then leads to the question of dose.

In scenario 1 you have a bulk meal that is all sitting in the danger zone for 1.5 hours, which could provide a massive inoculuum of bacteria when eaten. This is not directly comparable to eating in scenario 2, where it seems that it is only the plate that is in the danger zone for the whole time.

If in scenario 2 you are taking each component and reheating it separately on the same plate, such that the sum total of time for all the food components is 1.5 hours, then this is likely less risky than having a bulk of food all sitting in the danger zone for 1.5 hours. In this case the plate could be providing an inoculum to the food that enhances growth once the food is reheated, but how big a component to the risk this is, is very hard to say as it will depend on the bacterial species (and all the biological complexity there) and just how much of it is there before the food is added, and what food components it is multiplying on.

However, and this is the important bit: We can't tell for sure which of these scenarios is more likely to be a problem. It would take extensive scientific testing to prove it. Take all that we say on the internet with a grain of salt because we are not all food safety experts (I'm a virologist for instance)

  • Ahh, I see! But hey, the microorganisms thing applies to everyone's mouth and body, though, not just mine (Though it might be the case that moreso for mine than most others'). For completeness, if one was to cut food into small pieces and pour it from the dish into their mouth from far away as to not introduce any spit into it at all, would both scenarios be similarly safe? Apr 7, 2021 at 21:02
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    @MrSimplemaker. The microbial stuff applies to everything - surfaces we touch, the air we breathe, soil, water etc, all have microbes in them to a greater or lesser extent. As the recent pandemic has demonstrated to most outside the scientific community, we are surrounded by a cloud of microorganisms, so as soon as you get within a few feet (say 2 m/7 ft) of the dish, you are providing some bacteria to it. You breathe on it, then it has definitely had some bacteria added to it.
    – bob1
    Apr 7, 2021 at 21:20
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    Correct. The bulk of the contamination is coming from the eating the previous night.'
    – bob1
    Apr 7, 2021 at 21:34
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    @MrSimplemaker I read it as you make a monster meal of separate components, eat half of each, put rest in the fridge. Next day take it out and eat all as one (scenario 1), or as separate dishes (scenario 2). If this is not the case, then the scenarios are not at all comparable as S1 has you eating half and the s2 would be re-making from fresh(?), unless in each case you prepped and cooked each meal from the start of the second day.
    – bob1
    Apr 7, 2021 at 21:45
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    @MrSimplemaker in that case, as you are using the same dish in S2, that is the riskier practice as you are inoculating the fresh food with contaminated.
    – bob1
    Apr 7, 2021 at 23:09

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