[Luciana]

Hello

I’m a Biologist and although I study vegetable oils I could not answer a question that soap makers asked to me.

In a saponification reaction (crude vegetable oil + (water + NaOH)), which fatty acids are saponified first? AGL vs triglycerides? Short-chain vs long chain? Saturated vs unsaturated? In short, is there a saponifiation sequence?

In practical terms, this likely affects the quality of soap supperfat (smoothness, hardness etc).

I hope you can help me.

Thanks a lot!

[Babcock_Hall]

I am not familiar with the abbreviation AGL.  I suspect that the rate of saponification is going to depend partially on the accessibility of the NaOH (which is aqueous) to the hydrophobic TAGs.  Therefore my prediction is that the short chain fatty acids might be hydrolyzed a little bit more quickly but that saturation will not matter much.  I am not sure whether or not there are any studies on this question.  just my opinion.

[Luciana]

Sorry by the AGL (it means FFA, free fatty acid).

I also suspected that shorter chains saponify first, and it is a shame that no studies address this issue...

Anyway, thank you very much!

[Archer]

I also suspected that shorter chains saponify first, and it is a shame that no studies address this issue...

I have some experience of this in isolating specific mono-unsaturated fats from seed oils.

In short saponification of mixtures triglycerides is not that simple to model. The rate of the reaction is dictated by how intimate the contact between the aqueous hydroxide and the hydrophobic triglyceride is.

Granted the smaller chains will, in principal, be favoured in the reaction but this would not be exclusive in a mixture (i.e. no fractional saponification is possible). The modelling of this process becomes much more complex once the fats begin to saponify, as the first few percent which is converted to "soap" aids the formation of an emulsion (micelles) of the remaining triglycerides and water so the reaction becomes much more chaotic.

If you wanted to fractionate fats then you would be better off making methyl esters (FAME) and fractionally distilling them to separate into low - medium - and high boiling FAME's which may give you the difference in soap properties that you are looking for.

[Luciana]

Thank you E.M. Foster

I thought the reaction was dynamic, but not that complex. But in the "chaotic saponification environment", do you know if saponification of saturated fatty acids is facilitated in relation to  MUFA, and that of MUFA in relation to PUFA?

L.

[billnotgatez]

MUFA (MonoUnsaturated Fatty Acid)
PUFA (Polyunsaturated fatty acids)
From WIKI