Moisturizing

[The Efficacious Gentleman]

In the UK, there are 3 dates for products -

Sell by: after which the shop should no longer sell the product

Use by: an expiration date. Found on short lived and/or dangerous when off products (milk, meat etc)

Best before: the date to which the manufacturer will assure quality. After that, it might well be fine for years but the company will not assume responsibility for anything.

As most oils fall in to the last category, I would take the dates for the majority of oils with a pinch of sodium lactate.

 

[mymy]

I see. No worries then. So happy to know this info. Thank you guys!

 

[ngian]

On top of that, saponified fat (soap) has a longer shelf life than the fat from which it was made. You will know soap (or a fat) is not good by unpleasant changes in appearance and a rancid or "off" smell -- if it ever goes bad at all.

DeeAnna do you mean that the saponified mono & polyunsaturated fatty acids (Sodium of Oleate, Linoleate & Linolenate) can go rancid just like the unsaponified ones (Oleic, Linoleic, Linolenic fatty acids) but much much more later?

I thought that DOS was the rancidity happening only on the unsaponified fatty acids (because of superfat / lye discount) on a soap bar and all the sodium types of the above fatty acids would stay young just like table salt can help keep salted food somehow fresh. This is just a guess and for sure I need more info on that.

ETA: after reading this
Salt’s Role in the Prevention of Microbial Growth
I guess that the sodium of the oil's fatty acids have not the same ability with table salt (sodium and chloride ions).

Best before: the date to which the manufacturer will assure quality. After that, it might well be fine for years but the company will not assume responsibility for anything.

As most oils fall in to the last category, I would take the dates for the majority of oils with a pinch of sodium lactate.

Craig what does sodium lactate bring to the unsaponified oils? Did you mean to write sodium citrate?

ETA:
After reading this
https://en.wikipedia.org/wiki/Sodium_lactate
I understood that apart from being a soap additive your are using it straight to the oils as a food preservative, but I guess it is not as strong as Rosemary oleoresin (ROE).

 

[The Efficacious Gentleman]

Sorry, ngian - it was a play on the term 'a pinch of salt'. If you say 'take it with a pinch of salt' it means that you shouldn't believe too exactly on it and take it as a constant perfect rule

 

[DeeAnna]

"...DeeAnna do you mean that the saponified mono & polyunsaturated fatty acids (Sodium of Oleate, Linoleate & Linolenate) can go rancid just like the unsaponified ones (Oleic, Linoleic, Linolenic fatty acids) but much much more later?..."

I'm not any expert on this issue, but I do know these things from my reading --

There are two chemical processes that break down fats and fatty acids -- oxidation and rancidity. The first series of chemical reactions of a fat or fatty acid is the reaction with oxygen (oxidation) and/or with water (hydrolysis). These reactions can be catalyzed (accelerated) by exposure to light, water, and oxygen, and by contamination with certain metals. Fats hydrolyze into fatty acids and glycerin. If there are double bonds (monounsaturated and polyunsaturated) in the fatty acids, then oxidation breaks those double bonds in the fatty acid. Even the saturated fatty acids will eventually begin to oxidize, although more slowly than the unsaturated fatty acids.

If you don't believe me, then think about the fact that we humans eat fat in our diet for energy. Our bodies oxidize the fats and break them down. If fats could not be oxidized, then we could not use fats as an energy source!

After the initial hydrolysis and oxidation of fats and fatty acids, chemical reactions continue that lead to rancidity -- the off color and odor that result from the ongoing breakdown of the fatty acids into aldehydes and other smelly compounds.

I know the thinking is that the sodium part of the soap molecule somehow prevents it from oxidizing and eventually becoming rancid. While I think the sodium (or potassium) ions that make up the soap molecule and the unique crystalline structure of solid (bar) soaps can slow oxidation compared to the original fatty acids used to make the soap, I don't think the sodium and crystalline structure are absolute protection. Commercial soap makers make soap (at least in the US market) with little or no superfat. Even they are concerned about preventing oxidation and rancidity that lead to color changes and off odors. If only the superfat (unsaponified fats) were the ONLY parts of soap that could become rancid, then the commercial makers would have nothing to worry about.

 

[ngian]

It is not that I don't believe you DeeAnna, I'm just trying to suck every little drop of your knowledge upon these issues.

Thank you for your answer.

 

[DeeAnna]

Nikos, forgot you are not a native English speaker. "If you don't believe me" is a rhetorical phrase in English. My apologies for the confusion.

I used this phrase to mean something like this: "If what I am saying seems to be unclear, then here's an example from everyday life that might make the idea more understandable."

I DO think you believe what I'm saying (or at least that you take me seriously).