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This accepted answer about knife cleaning seems to presume that soap sanitizes:

...in household use soap is required to sanitize your knife blade.

However, a cursory search seems to undermine the presumption that soap kills germs:

  1. This ask alice post states the following:

    Regular household soap or cleanser does not kill germs — rather, it suspends (or lifts) them off the skin surface, allowing the microscopic critters to be rinsed down the drain.

  2. The wikipedia definition for soap does not seem to suggest that soap, in general, has any germicidal properties.

  3. This white paper on disinfecting in child care does not even consider soap for killing germs other than to clean a surface prior to.

  4. From personal experience, I have encountered numerous liquid soap storage containers that were clearly culturing a colony of one life form or another.

So, does soap really kill germs?

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alx9r
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  • Not only does this seem only tangentially about cooking- it seems like you have already exhaustively answered it yourself. – Sobachatina Jan 14 '13 at 23:36
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    I wrote an answer because it seems to get at the notion of "what is good sanititation" which is, I think, on topic. I think asking for more definitive and credible answers than provided by whatever "Ask Alice" is, or by Wikipedia is also not unreasonable. This is far from the craziest question I have seen here :-) – SAJ14SAJ Jan 14 '13 at 23:42
  • Good point. I retract my criticism. – Sobachatina Jan 15 '13 at 15:27
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    It's worth emphasizing that all of this suggests that soap does help *get rid of* germs; it's just that it doesn't do so by killing them. I could unfortunately see people skimming this and the answer and saying "oh, I shouldn't bother with soap!" – Cascabel Jan 16 '13 at 06:03
  • @Jefromi - I see your point. Hopefully that clickable pictorial at the bottom helps skimmers with that point. – alx9r Jan 16 '13 at 20:20
  • @alx9r I am afraid I rolled that back as it was a substantial change to the tenor of the question being asked. I suggest adding that information in a comment or an additional answer. – SAJ14SAJ Jan 16 '13 at 21:16
  • @SAJ14SAJ Understood. I actually don't think trying to protect against misinterpretation by those skimming questions is productive. I think doing so creates a distraction from the true topic under discussion. – alx9r Jan 16 '13 at 22:49

1 Answers1

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No, soap does not kill germs in general. It facilitates washing foreign matter, dirt, and so on (which may host pathogens) from the hands. There are some soaps with antibacterial agents added, but I won't go into whether they are effective, or even a good idea, as this is not the forum for that.

Typical food service sanitation standards (that is, the health codes) require either sanitzing agents or certain heat and time requirements (or both) in dishwashing to ensure proper sanitation. See this typical regulatory summary from one jurisdiction.

This FDA document may fall into the category of Too Much Information, but the point of hand washing in food service (as important as dishwashing) is to control fecal bacteria.

Even these requirements do not kill all germs, but are intended to get to a reasonable level of cleanliness and safety for the average population for the types of threats typically related to food preparation.

Hospitals and other labs that require all pathogens or microfauna to be killed must use much more stringent measures to sterilize, rather than sanitize.

Edit: Note that the referenced question about cleaning knives also has temperature standards (the time required is not mentioned in the post, but is important)--that is the real factor that provides sanitation, not the soap. With the reduced temperature, not that the post talks about the need for "chemical additives" which would be sanitizing agents of one sort or another.

I believe the part of the referenced answer that concludes in the author's opinion that should use soap to sanitize is... well... its not quite correct. There is more to cleanliness than sanitization (reduction of pathogens). Its just that soap doesn't help with the sanitization part other than removing foreign matter which may provide a place for the pathogens to grow.

Most home folks will never truly sanitize without the use of a dishwasher as the water from the hot water heater is simply not hot enough, and most homes don't have three compartment sinks where the middle sink is used for a sanitizer dunk.

SAJ14SAJ
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    And on the flip side, bleach does not clean anything. As I was taught in my first sanitation class, you can be clean but not sanitary and you can be sanitary but not clean. – Rob Jan 15 '13 at 03:31