Also Known as PGEs
What are Polyglycerol Esters?
Polyglycerol esters of fatty acids (PGEs) are used in food as an emulsifier. PGEs are a class of synthetic, nonionic surfactant frequently used in food, pharmaceutical, and cosmetic industries on account of their amphiphilic properties. The hydrophilic part of these amphiphiles consists of oligomeric esters of glycerol, and the hydrophobic part consists of alkyl chains of varying length and degree of unsaturation.1
In foods, they are used as emulsifying agents in the production of baked goods, chewing gum, and in replacement of fats.
PGEs have been used as food additives in Europe and America since the 1940s and they were approved for food use in the U.S. in the 1960s.2 Figure 1 is the structure for polyglycerol monoester.
PGEs are produced by polymerization of glycerol in the presence of an alkaline catalyst followed by esterification with fatty acids.1 The fatty acids are from corn oil, cottonseed oil, lard, palm oil, peanut oil, sesame oil, sunflower oil, soybean oil, etc.3 Besides esters, PGEs also contain impurities, like mono, di, and triglycerides, free fatty acids, free glycerol and polyglycerol, and sodium salts of fatty acids may be present.
Components of bakery products, such as oil, water and flour, are not soluble in each other. Interfaces are present between these substances, such as water and oil, gases (air bubbles) and solid substances (flour components), air and water. PGEs, like other emulsifiers, have both a hydrophobic and hydrophilic nature so they can reduce interfacial tension between different phases.
PGEs' hydrophilic-lipophilic balance (HLB) depends on the length of the polyglycerol chain and the degree of esterification. The HLB can vary from 3 to 14, and the desired HLB value may be obtained by appropriate blending. Depending upon their HLB, PGEs can act as water-in-oil (W/O) or oil-in-water (O/W) emulsifiers.
PGEs form highly stable alpha-gel in water. The α-gel phase of PGEs is surface active and is able to stabilize foams when the temperature is lower than the melting temperature of the emulsifier. The special structure also leads to better emulsification properties.
An important application of PGEs is in cake batters with little or no content of fat and oil (i.e. batters for sponge cakes, Swiss rolls...