If mayonnaise is mostly eggs and oil, what's in fat-free mayonnaise? If fat makes cakes light and airy, why isn't fat-free cake rubbery? If whipping cream and eggs make ice cream creamy smooth, what does the job in fat-free ice cream?
The answer: commercial thickeners.
The labels call them gums: agar, xanthan, carob bean or guar gum, carrageenan, maltodextrin. These sticky substances have all passed rigorous Food and Drug Administration safety testing. They are similar to natural polymers that are added to regular salad dressing to keep the oil and vinegar from separating. (The protein in eggs, for example, is a natural polymer that stabilizes the emulsion of fat and water in mayonnaise for longer shelf life.)
But what are they really? Gums are synthesized from starches and proteins found in corn and seaweed to make foods hold water and contribute smoothness. According to Webster's New World Dictionary, agar is "A gelatinous product made from seaweed . . . used as a laxative, in jellied and preserved foods." "Carrageenan is a purplish, edible red algae . . . used in jellies, lotions, medicines, etc." "Dextrin is any of a number of water-soluble, gummy, dextrorotatory polysaccharides obtained from the breakdown of starch and used as adhesives, as sizes and in certain foods." And, "xanthan gum is a gum produced by bacterial fermentation, used as a thickener, as in commercial foods."