What exactly are polyols and why are they so effective in reducing the carbohydrate content of frozen desserts?
Polyols are sugar alcohols. They are derived from sugar, but not processed by the body like sugar. Chemically, part of the structure resembles sugar and part resembles alcohol, as polyols are derived from carbohydrates whose carbonyl group has been reduced to a primary or secondary hydroxyl group.
Some of the polyols that have application as food ingredients includes erythritol, glycerin, hydrogenated starch hydrolysates (HSH), isomalt, lactitol, maltitol, maltitol syrups, mannitol, sorbitol and xylitol. These food ingredients have been available for some time, however, their use in the dairy industry has been minimal . . . but that is changing, and very rapidly.
This is because polyols are classified as low-glycemic carbohydrates. Glycemic index is the relative rate at which glucose appears in the blood after one consumes food. High-glycemic sugars such as sucrose enter the bloodstream quickly, stimulating the production of insulin. Insulin assists in removing sugar from the blood and storing it in the cells of the body. This is undesirable for diabetics who do not produce their own, or enough of their own insulin. It is better for them to consume low-glycemic carbohydrates so that the sugars enter the bloodstream slowly over a long period of time. Low-carb dieters also avoid high-glycemic carbohydrates.
Thus, traditional ice cream, with its relatively high sucrose content, is not suitable for diabetics or low-carb dieters. The deal with sucrose, though, is not only does it sweeten ice cream, it also adds solids, providing essential bulk, texture and body. It acts as a foundation for, and enhancer of added flavors, and provides a means to control freezing point, affecting frozen dessert hardness and scoopability. When high-intensity sweeteners are used to replace sucrose, it is necessary to add solids that do not contribute energy in the form of glucose in order to replace the solids that were provided by sucrose. This typically requires flavor and process adjustments.
In general, polyols provide ice cream mix with both sweetness and bulk. And like sucrose, most polyols are effective in lowering freezing points because they are similar in composition and molecular weight.
Sorbitol, for example, can effectively replace all the sucrose in ice cream, but consumption levels of sorbitol must be limited because of sorbitol's laxative nature. This is not something a marketer wants to be associated with. Take it from the olestra folks.
Recent research conducted at Penn State University showed that a specific maltitol syrup is able to replace all of the added sugar in ice cream without the addition of bulking agents or high-intensity sweeteners. The syrup contains 25% water, and handles like sucrose solutions. The molecular weights of maltitol and sucrose are very similar, and the two have comparable solubilities and relative effects on freezing point depression. At the recommended replacement levels, the maltitol syrup exhibits the sweetness of sucrose, does not require adjustments for freezing point like some other polyols require and is easily adaptable to ice creams with fat contents of 8% or higher.
As mentioned, another way to lower carbohydrates in frozen desserts is to take a systems approach. For example, at the recent Worldwide Food Expo, a low-glycemic, no-sugar-added ice cream was sampled that was made with an ingredient blend of lactitol, polydextrose, mono and diglycerides, locust bean gum, cellulose gum, guar gum, sucralose and carrageen.
Another supplier showed how erythritol can be used at levels up to 10% in frozen dairy desserts along with most intense sweeteners.
Because most ice cream manufacturing handbooks and textbooks do not address the use of polyols in mix formulations, it is necessary to work closely with suppliers of polyols, stabilizers and high-intensity sweeteners to identify your company's perfect, signature, low-carb frozen dessert formulation. Good luck.