Polyglyceryl Polyricinoleate
Three names, two CAS numbers, one identity problem

A pale yellow liquid, thinner than it should be, in a bottle labelled with an INCI name we had ordered against a CAS number we had specified.

Polyglyceryl-6 polyricinoleate is a heavy material. Castor oil is already a thick oil; a polyglycerol ester of polymerised ricinoleic acid should be thicker still. What we poured moved like a light oil.

That is a flag, not a finding. Colour and viscosity judged by eye are worth nothing as evidence, and this file exists precisely because we are not willing to treat them as such. But it was enough to make us ask whether the paperwork in the box described the liquid in the bottle — and to discover that we had no way to check.

A water-in-oil emulsion. In an oil-in-water cream — most lotions you have used — tiny droplets of oil float in a continuous phase of water. A water-in-oil emulsion is the reverse: droplets of water suspended inside a continuous oil phase. It feels richer, resists water better, and is much harder to stabilise.

Holding it together needs an emulsifier that prefers oil to water. Chemists describe that preference with a number called HLB, for hydrophilic-lipophilic balance. Low HLB means oil-loving. Water-in-oil emulsifiers sit at the low end, usually around 3 to 4.

Polyglyceryl-6 polyricinoleate is specified for exactly this job, and particularly for emulsions with a high internal water phase — meaning it should hold a lot of water inside the oil.

Two pieces, esterified together. The backbone is polyglycerol — glycerol molecules linked into a short chain. The number in the INCI name is the chain length: polyglyceryl-3 means roughly three glycerol units, polyglyceryl-6 roughly six. This is the water-liking end.

The tail is polyricinoleate: ricinoleic acid from castor oil, but polymerised. Ricinoleic acid is unusual among fatty acids in carrying a hydroxyl group partway along its chain. That hydroxyl lets one molecule esterify to the next, forming chains called estolides. This is the oil-liking end, and it is bulky.

One consequence matters later in this file: the polymerisation consumes hydroxyl groups. Castor oil is full of free hydroxyls. A properly made polyricinoleate has spent many of them building estolides — and that difference is cheap to measure.

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Read the CAS row again.

Polyglyceryl-3 polyricinoleate and food-grade PGPR share a CAS number. They are, for registry purposes, the same substance — and the cosmetic INCI entry for polyglyceryl-3 polyricinoleate is itself commonly abbreviated PGPR.

So a supplier offering PGPR with a certificate referencing the food additive E476 is not necessarily doing anything dishonest. They may be selling precisely what they say, under the name the food industry uses for it.

Polyglyceryl-6 polyricinoleate is a different registry entry: 107615-51-0. Longer backbone, different water-holding behaviour, different CAS.

That is a documentable mismatch on paper. It needs no laboratory to detect, and no accusation to state.

Is polyglyceryl-3 polyricinoleate the same as food-grade PGPR?

By CAS registry, yes. What differs is the specification each grade is held to: permitted impurity limits, residual solvents, heavy metals, and the documentation regime behind them. Food-grade E476 has published specifications and a defined acceptable daily intake. Cosmetic grade carries no equivalent universal monograph.

The honest position is narrower than food grade is fake. It is this: the name tells you the chemistry, not the purity, and not the chain length.

Across the samples we requested, a pattern.

• No batch number. The certificate describes a material in the abstract, not the container in front of us. A certificate of analysis without a lot number is not a certificate of analysis; it is a brochure.
• Identical digital formatting across unrelated vendors, suggesting a common origin document rather than independent testing.
• Grade language that drifts between the cosmetic INCI and the food additive within the same document.

We are not naming vendors. Not out of diplomacy, but because we have no analytical data, and an accusation without data is worth nothing — including to us. When we have numbers, we will publish the numbers.

Stating the method before we have results, so the result cannot be accused of being fitted to the grievance.

Because the finished version would be less useful. Most raw material problems in this industry are resolved privately, or not at all, and the knowledge dies inside one lab. A file left open — with the method fixed in advance and the disproof condition stated — is something another formulator can check, argue with, or run themselves.

Subsequent files follow the same structure. Next: PEG-6 and PEG-7 triglycerides.