Emulsifiers are used to disperse tiny globules of one liquid in another so that they will stay mixed. Their use has made it possible to market oil-containing foods, such as peanut butter and margarines, that will not separate and so are instantly usable. Emulsifiers are used extensively in the baking industry to help increase volume and to effect the fineness of the grain. Stabilizers and thickeners are used to bind together solids and liquids so that they will not separate. They are used in ice-cream, many cake and pudding mixes, cheese spreads, salad dressings, soups and many others too numerous to mention.
Most commercial stabilizers and thickeners are pure plant extracts, and the use of plant gums for this purpose, is quite extensive. Gums are extracted from seaweed, trees and seeds, while cellulose derivatives are obtained from wood pulp and cotton. The seaweed extracts include agar, algin, carrageenan and furcellaran. The tree gums include arabic, ghatti, karaya, larch and tragacanth. Then there are still extracts of seeds which include guar, and extracts from the carob bean, and finally the commonly used cellulose derivatives are methylcellulose, carboxymethyl-cellulose and hydroxypropyl-methylcellulose. The most commonly used natural emulsifier is lecithin which is obtained from soybeans and other vegetable oils, but synthetic mono-, di- and triglycerides are also extensively used. Synthetic stabilizers and emulsifiers are used extensively in the baking and dairy industry, and in the UK the permitted substances include stearyl tartrate, complete glycerol esters, partial glycerol esters, partial polyglycerol esters, propylene glycol esters, monosteatrin sodium sulphoacetate, Sorbitan esters of fatty acids and their polyoxyethylene derivatives, cellulose ethers, sodium carboxymethyl cellulose and acetic and tartaric acid esters of mono- and diglycerides. Some of these compounds are suspected to be carcinogens, and approval for the use of some of the polyoxyethylene compounds has been withdrawn in some countries.