1,2,3-Propanetriol, homopolymer, (9Z,12R)-12-hydroxy-9-octadecenoate
polyglycerol ricinoleic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Polyglycerol polyricinoleate (PGPR), E476, is an emulsifier made in a three-step process from glycerol and fatty acids (usually castor bean derived). 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 can be used at low levels (below 1%); however, ingredients lists in chocolate are typically listed before the 2% and under section. This indicates it could be above 1% of the total product. 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 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.
In a 1998 review funded by Unilever of safety evaluations from the late 1950s and early 1960s, "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, no evidence was found of interference with normal fat metabolism, nor with growth, reproduction, and maintenance of tissue. Overall, it did not "constitute a human health hazard."
The Food and Drug Administration (FDA) has officially deemed PGPR safe for human consumption, setting the accepted daily intake from 0 to 7.5 milligrams per kilogram of body weight. Short-term studies on rats and chickens showed reversible liver enlargement as a result of higher doses of PGPR, but those were deemed a result of increased hepatic workload.
Glycerol is heated to above 200 °C in a reactor in the presence of an alkaline catalyst to create polyglycerol. Castor oil fatty acids are separately heated to above 200 °C, to create interesterified ricinoleic fatty acids. The polyglycerol and the interesterified ricinoleic fatty acids are then mixed to create PGPR.
Use in chocolate candy bars
PGPR is used by chocolate makers to reduce their costs of raw materials. Since 2006, commercial-grade candy bars, such as those made by Hersheys and Nestlé, made an industry-wide switch to include PGPR as an ingredient - a possible indicator of a cost-saving measure by the commercial chocolate industry. Makers of PGPR, such as Danisco and Palsgaard, indicate PGPR can be used to replace the traditional but more expensive cocoa butter as an ingredient in chocolate. Palsgaard's website asserts, "Cocoa butter is an expensive raw material for chocolate manufacturers. By using PALSGAARD 4150 the chocolate recipe has lower costs in terms of less cocoa butter but also gives the benefit of having less fat."
However, the 1996 study conducted by Andrew Waterhouse of UC Davis which discovered the phenols (potent antioxidants) in chocolate also revealed that these antioxidants come from cocoa butter and the stearic acid it produces. It demonstrated that the phenols prevented LDL cholesterol from building up in arteries. Another study had subjects follow diets in which the majority of fat calories came from either chocolate or butter; only those with the butterfat diet showed an increase in LDL cholesterol. 
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