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Ask the Experts – Saponification

Posted by on September 6, 2011 · 6 Comments 

Question:

Hi!

I want to ask an expert this:

Does the alkaline environment or the saponification process itself of handmade soaps destroys any benefit from additives such as essential oils, herbs, oils infused with herbs components, honey, juices etc.? I have read somewhere that squalene for example from olive oil can resist saponification or alkalinity (and maybe other “unsaponifiables” too).

Thank you, my best wishes to your honest website.

Scott

 

Answer:

In short, no, saponification will not destroy most benefits of additives. Lets see why.

The chemical reaction that makes soap is called saponification. The reaction involves breaking the ester bond of a fat (triglyceride) using alkali, or lye. Once this bond is broken the result is glycerin (or glycerol, same thing) and fatty acid salts formed with the sodium of sodium hydroxide (lye). A strong alkali or base environment (high pH) is necessary to split the bond. Lets take a look at squalene that you mentioned.

Unlike a triglyceride, squalene has no ester bond that can be split by the lye, therefore it does not react. Molecules like this are categorized as ‘nonsaponifiable or unsaponifiable’ and there are many of them found in oils and fats; some more than others.

Lets look at herb extracts. Herbs have a variety of benefits so it depends on what you are after. The main reason I use herbs is for their flavonoid (antioxidant) content. Generally, flavonoids are very stable to alkali and heat (although I’m sure there are exceptions) so they would be fine in soap. Another benefit of herbs is the vitamins they contain such as A, C, K. These are going to be less stable, both due to the alkali environment and the heat of the reaction. For juices, it depends. Large polysaccharides found in aloe juice are pretty stable to heat and pH, as are the flavonoids found in juices. But the vitamins; probably not.

Essential oils are typically added late in the process because, even though they are probably stable, they are also volatile and the heat of the reaction will cause them to vaporize and escape rather than stay in the soap.

Now none of this has been really studied or proven that I know of. I’m just making guesstimations based on what I know about chemical stability. If anyone else has ideas, I’d like to hear them.

Cindy Jones, Ph.D.

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More about the author:  Cindy Jones is a formulator and microbiologist. After receiving a Ph.D. in biochemistry from the University of Cincinnati she worked in cancer research, later as a health/medical writer and now in cosmetic science. Read more from this author

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  • Scott Freem

    Dear Cindy Jones,thank you very much for your answer!  Reading also an older article from you about calendula, one may be sure that the saponification of an olive oil infused with calendula petals will not invalidate flower’s benefits for the skin.Greetings from Greece,  Scott Freem.

    • Cindy

      Yes, I feel pretty comfortable that calendula infused olive oil will retain benefits in a soap. Maybe someday this type of stuff will be scientifically studied so we know for sure, but based on what we already know, calendula should be great in soap.

  • Swifty

    It’s quite an assumption that these materials added to soaps offer any benefit to begin with.

    • http://twitter.com/SueApitoLikes Sue Sawhill Apito

      Feel free to offer proof that the additives people put in soap don’t offer any benefit.  Because I worked for the Handcrafted Soap Makers Guild for a number of years and those folks would disagree with you based on their research AND the experiences of their customers.

      • swifty

        Yea, ok – that constitutes proof.  Thanks for clearing that up.  :-)

  • Donna Davis

    I am SO glad to see this discussion!  i have a related question: do substances that are highly comedogenic retain that quality through the saponification process?  Coconut oil, for example, is a 4 out of 5 on the comedogenic scale, so is something I would not normally put on my face.  I have NO idea what chemistry is involved in that property.  I think the comedogenic scale is based on animal experiments: what substances clogged the pores of the rabbits’ ears?