ABSTRACT
Most dietary fat calories come from the ingestion of triacylglycerols (TAGs) since they are the most abundant lipid forms in both plants and animals. Because most lipids, including TAGs, are practically water-insoluble, fat digestion must be aided by bile salts to form a coarse emulsion in the small intestine. As digestion proceeds, the triacylglycerol lipid droplets form micelles, which renders them more accessible to digestion by lipases secreted into the intestine from the pancreas. Hydrolysis of TAGs by pancreatic lipases liberates free fatty acids (FFA) from the sn-1, 3 positions of the TAGs leaving 2-monoacylglycerols as remnants.1 For the body to use these lipids they must first be absorbed from the small intestine. At the surface of the intestinal tract, the liberated free fatty acids and monoacylglycerols diffuse into the epithelial cells where TAGs re-synthesis occurs. The newly synthesized TAGs are transported as chylomicra into the blood stream via the lymphatic system and transported to the liver, adipose tissue, and the muscular and other organs for oxidation or storage.2,3 Because lipids in general have higher caloric content (~9 Kcal/gram) than proteins or carbohydrates, they are the main fuel for the body. For fatty acids with carbon-chain length <12, however, their metabolism is quite different. Short-and medium-chain fatty acids of C2 to C12 in carbon chain length have a caloric value of ~5 Kcal/gram or less due to their shorter chain length. This characteristic makes such fatty acids attractive for use in low-calorie applications. Because their adsorption occurs by transport through the portal system, they are metabolized more rapidly than long-chain fatty acid and because of this are utilized also in dietary energy supplements.4-6
Generally, fats and oils contribute palatability, flavor, creaminess, and mouthfeel to foods, transmit heat rapidly and uniformly, evaporate moisture, and provide crisp texture in fried foods. Despite these attractive properties, researchers have sought ways to reduce the lipid content of foods with other materials as a way of reducing their caloric content. The ideal fat substitute should impart most attributes
of a fat while reducing the calorie content of the food, which is not an easy task. Several types of fat substitutes have been developed, that chemically and physically resemble fats and oils and generally fall into three broad categories: carbohydrates, proteins, and fat analogs. Carbohydrates and proteins are fat mimetics that interact with water to provide some of the functionality of a fat. Carbohydrate-based fat substitutes can be made from gums, algins, starches, or fibers. They form a gel with water and provide the mouthfeel (creaminess) and body of fat but are not stable when heated. Oatrim (Beta-Trim®, TrimChoice®) is one example and is made from enzyme-treated oat flour. It can be used in place of conventional fats in food manufacturing for baked products, processed meat products, spreads, soups, and frozen desserts.7
