E 471: Mono- and diglycerides of fatty acids

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Notorious Lyear
Jan 14, 2021
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Another dual-use good that has its original place in bakery, but turns out to be of possible use for soapmaking as well: mono- and diglycerides of fatty acids, aka E471.

Since its use is so ubiquitous in bakery, I have ordered some a few years ago (1 kg was the smallest package size). Didn't noticeably improve bread and pastry, but I had it at hand, so I looked into its properties and value for soap.

It is a versatile emulsifier that is meant to interact with starch (intercalation in amylose helices), stabilise fat-water interfaces in batters and doughs and so on.
Its chemical structure is fat molecules, partially broken down with one or two fatty acids missing. Naturally it occurs in (rancid) fats. During lye-based saponification, each fat molecule will first become a diglyceride (one FA molecule split off), then a monoglyceride (second FA split off), and finally glycerol (free floating backbone). So in some way E471 is a major constituent of (young) soap batter anyway – why not add it deliberately?

It comes as a white powder, which looks similar to sugar, but has a waxy feel to it. The packaging calls it “plant-based”, but does not give any hint which plants/oils it comes from, nor other important things to know about it. So it's up to us to find out ourselves…

The white powder melts in a range between 63°C (becomes sticky) and 74°C (fused into a clear liquid). Once solidified, it strikingly resembles paraffin wax: colourless and translucent, with a matte surface. It freely dissolves into (or rather: is miscible with) into oils at elevated temperature, and gels to a murky, tallow-like paste upon cooling.

Most important for soapmaking is its saponification value, and one can find it out by titration. So I made a lye-heavy soap from it. Which sounds easier as it was – in contact with water/lye it converts into a gel-phase like cement that is nearly impossible to knead without addition of crazy amounts of water (10…20 times and more of its weight). After a tedious HP session, I had something that looked like wood glue, just that it solidified to a chunk literally as hard as concrete. Well, I just needed to know the total weight of the soap, and a bit of it for the titration. I grated down said bit and tried to dissolve it in water – to no avail, until I heated it in the microwave. Clear, with some froth on top until it solidified into a gel upon cooling below 50°C at 10% solution! That means … hot titration, keeping the soap fluid in a water bath, eww.
However, I back-titrated with acetic acid against phenolphthalein. The equivalence point (disappearance of the pink colour) was not easy to observe, since the free fatty acids made the solution murky, and equilibration took a really long time. Titration is a dirty business, but when one of the reactands is aggressively insoluble, it doesn't exactly make things easier … Accordingly unprecise are the numbers. Take SAP=0.110 if you accept only the last bits of phenolphthalein bleached; but SAP=0.130 was closer to what I'm used to accept as the colour change at the equivalence point – and somewhat more in line with possible constitution guesses.

Oof. That was the worst part of it. Which other indications to collect? Acidification the hot solution with citric acid gives (like any soap) free fatty acids, that coalesce into an oily layer floating on top of the aqueous phase. Only a very faint capric smell (like rancid coconut milk) indicates that lauric oils (coconut, palm kernel) are, at most, minor components of the original fats. Liquid at 56°C, the fatty acid layer turns solid at 51°C and floats arond in curd-like flakes.

We draw the following conclusions from our observations: The high melting point of the FFA and the waxy appearance suggest a high content of long-chain saturated fatty acids. Let's have a closer look at the melting point: Stearic acid melts at 69°C, palmitic acid at 62°C, but an eutectic mix of the two (roughly P:S=2:1) melts as low as 52.3°C. Considerable presence of both acids fit well with my observed melting point (deviations due to other impurities (water!) are likely), as well as with the saponification value.

The best-effort conclusion is that (my batch of) E471 consists of glycerol backbones esterified with one or two FAs each, and those FAs are mostly palmitic and stearic in similar quantities. Shelf life, and the hardness of the original material, the soap, and the FFAs derived from it rule out major percentages of unsaturated fatty acids.

This leaves as the “only” remaining question the botanical origin. Without information from the manufacturer, it appears reasonable to assume that the FAs are sourced from hydrogenated palm oil. Two major reasons come to my mind: First, the ratio of C16:C18 FAs in palm oil is roughly 1:1, so full hydrogenation gives about this P:S ratio, vastly different from soy, canola or sunflower (Against soy and canola is that it is GMO-free). Secondly, palm oil and its derivatives (stearin, distilled palm FFAs, etc.) are a staple chemical within one of the largest vegetable oil industries, cheap and with well-proven global supply chains.

E471 and soapmaking
What is it good for now, that this forum is the right place to post my findings here? Well, in the first place, I have it, and I'd be happy if it finds a sensible use besides bakery additives (and maybe margarine 😉).
Since it appears to be mostly palmitic/stearic acid (just in partially esterified form) it can replace the FFAs like stearic acid flakes used for some soap formulations (shave soap, M&P base…), without the hassle of instantaneous solidification upon lye addition.
As a highly concentrated source of “hard” FAs, it is useful to formulate soap recipes with a high fraction of soft oils, but still with agreeable hardness, longevity, and comfortable cure times (I liked a first simple test batch from 60% HO safflower, and each 20% coconut oil and E471 a lot).
Plus, it is an emulsifier, i. e. it helps to hold a mixture of oils and (lye) water somewhat stable, maybe speed up trace. Since it is a simple, non-ionic molecule, it probably isn't as sensitive to salt concentration and lye like soap or lecithin are. I haven't made systematic research yet, but there are a few observations that look promising for people who aren't fond of cleaning their stick blenders.
E471, at least in the form I've got, has intermediate green-labelling appeal. Even more than in food, it is not an additive since it consists of nothing that wouldn't be in the soap anyway. Likely based on conventional palm agriculture, it carries some ecological question marks with it, but this is not a property of the substance class as a whole.
All in lal, it is not particularly economical (for me). At about 10…15 €/kg, its place besides soy wax & friends is limited to specialty uses, should someone want to carry E471 out of the lab into the shops.

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