Polyglycerol polyricinoleate (PGPR), E476, is an emulsifier made in a three step process from glycerol and fatty acids (usually castor bean), respectively. PGPR reduces the viscosity of chocolate and similar coatings and compounds. It works by decreasing the friction between the particles of cacao, sugar, milk, etc. present so they can flow more easily when melted. It is used at low levels (below 1%). It is made up of a short chain of glycerol molecules connected by ether bonds, with ricinoleic acid side chains connected by ester bonds.
PGPR is a yellowish, viscous liquid composed of polyglycerol esters of polycondensed fatty acids from castor oil. It may also be polyglycerol esters of dimerized fatty acids of soybean oil.
PGPR is strongly lipophilic, soluble in fats and oils and insoluble in water and ethyl alcohol. In chocolates, it is used as a viscosity-reducing agent. It is virtually always paired with lecithin or another plastic viscosity-reducing agent.
It can also be used as an emulsifier in spreads and in salad dressings or as a crystal inhibitor and anticlouding agent in fractionated vegetable oils.
In a study in 1998, "PGPR was found to be 98% digested by rats and utilized as a source of energy superior to starch and nearly equivalent to groundnut oil." Additionally, there was no evidence of interference with normal fat metabolism, nor with growth, reproduction, and maintenance of tissue. Overall, it did not "constitute a human health hazard."