Don't tallow based soaps go rancid?

[chrisf8657]

I have a question for the experts -

Since Tallow is a fat, and bacteria/molds LOVE fat, wouldn't the soap go rancid after a short period of time?

Thanks

 

[.soap.]

Good question. My unscientific understanding if this is that saponified fats =\= fats.
The molecules change enough via the saponification process enough that they are no longer volatile like their beginning ingredients.
That being said, some soap makers "superfat" and add additional oils that won't react with the (used up) lye. These fats/oils would be subject to going rancid under the wrong conditions.

 

[mblakele]

Right, soap is saponified fatty acids not fatty acids. Just like cooking transforms and preserves meat, saponification transforms and preserves fats and oils. If soap did go bad, though, vegetable formulations would be just as risky as tallow.

I have seen ordinary hand soap with something like mold growing in it, but one mold or another will grow on practically anything. Soap probably has about as much bacteria on it as anything else in your environment, too. But according to http://www.ncbi.nlm.nih.gov/pubmed/3402545 even soap that is highly contaminated with bacteria is unlikely to transmit disease.

 

[Go West Young Man]

My roll of 1950s vintage Williams that I use every day disagrees

 

[Jim]

Fats are saponified into salts. Remember life is too short to shave with a crappy soap.

 

[Kevan]

Cella has been known to go rancid. I don't know if it's the tallow or various oils in it that go bad, though.

 

[Early Morning]

Fats are saponified into salts. Remember life is too short to shave with a crappy soap.

That's how I understand it. Not sure about unsaponified saturated fats that might be added in addition to the soap, but I have heard it normally takes two years for some saturated fats to go rancid.

 

[chrisf8657]

Very interesting. Thank you to all.

 

[lt114]

My vintage Yardley that is at least 50 years old is doing just fine.

 

[geko29]

Cella has been known to go rancid. I don't know if it's the tallow or various oils in it that go bad, though.

It'd be the other oils. Tallow is a saturated fat, which means its very stable and highly resistant to oxidation (ie, going rancid), even before it's saponified. monounsaturated fats are easier to oxidize and go rancid rather easily. polyunsaturated fats oxidize incredibly easily and go rancid VERY quickly.