Energy Value of Medium-Chain Triglycerides in Muffins Fed to Rats

Cereal Chem. 71(6):553-556 This study was designed to determine the energy values of three fed MCTs deposited significantly (P < 0.05) less fat in their carcass than commercially available medium-chain triglycerides (MCTs), using young did those fed a conventional fat (baker's shortening). Primarily because rats as the test model. These MCTs, with slightly different C-8 to C of this, calculations showed that the MCTs tested had an average energy 10 fatty acid ratios, replaced shortening in a muffin formula and reprevalue of 6.9 ± 0.4 cal/g, a value about one-fourth lower than that of sented, through muffins added to the diet, 40% of total dietary energy. conventional fats. All MCTs were slightly better digested than the baker's The increase observed in rats' carcass energy due to MCTs fed over a shortening. three-week period formed the basis of calculating energy values. Rats Medium-chain triglycerides (MCTs), developed in the 1950s, have been primarily utilized in nutritional formulations as an energy source for individuals with disorders of fat assimilation. MCTs naturally occur in commercially significant amounts in milk fat, palm kernel oil, and coconut oil. Coconut oil is usually the source for commercially prepared MCTs, which are essentially composed of C-8 (caprylic) and C-10 (capric) fatty acids. MCTs are absorbed bypassing the lymphatic system (lymphatic system transports conventional long-chain triglycerides [LCTs]), going through the portal vein, and being transported directly to the liver (Bach and Babayan 1982). Rapidly oxidized in the liver, MCTs are, thus, metabolized more like carbohydrates than like conventional fat. As such, they may show a caloric value lower than that of conventional fats. It has also been reported that MCTs are less effectively incorporated into tissue lipids, therefore limiting the storage of body fat (Lavau and Hashim 1978, Geliebter et al 1983). The heat of combustion (gross energy) for MCTs, also called MCT oils, is reported as 8.3 cal/g (Bach and Babayan 1982, Babayan 1991). However, there is a paucity of information on how well this energy is utilized; the usable energy value of MCTs may be lower than 8.3 calories. It is also difficult to make a valid comparison of MCTs versus LCTs for their effect on body fat deposition, as several studies conducted with rats (Wiley and Leveille 1973, Lavau and Hashim 1978, Chanez et al 1991) did not equalize caloric intake from MCTs and LCTs. The study reported here was undertaken to address these questions. Young rats were used as the test model because they allow relatively simple whole-body analysis (the basis of the method used here). MCT oils were tested as added to a food product muffins. Being saturated fats, MCTs show a high degree of oxidative stability. MCT oils also show excellent solubility and solvency characteristics. The current food uses of MCTs include solvents for colors and flavors; antistick, moisture-barrier, or release agents for bakery products and candies; and ingredients in gloss-enhancing coatings. MCTs can also serve as the fat ingredient in fullfat, reduced-fat, or low-fat bakery products. Reduced-calorie foods such as peanut butter have been prepared with MCTs. Due to their extremely low viscosity, MCTs may also be suited as spray oil for use in cereals, crackers, and other snacks. MATERIALS AND METHODS Test Fats Partially hydrogenated soybean oil (baker's shortening), a commercial USP-grade heavy mineral oil, and three commercial 'American Institute of Baking, Manhattan, KS. © 1994 American Association of Cereal Chemists, Inc. sources of MCT oils (Table I) were tested. Mineral oil and MCT oils are odorless, tasteless, clear liquids. Muffin Preparation Test fats were used at the 22.3% level in muffin formula. Besides water, the other formula ingredients included flour (46.5%), sugar (25.5%), nonfat dry milk (2.8%), baking powder (1.9%), salt (0.5%), and dry egg white (0.5%). Baked muffins were air-dried, finely ground, and stored frozen until analyzed for proximate components (Table II). Test Diets Two control (shorteningand mineral oil-based) and three test (MCT-based) diets were prepared using finely ground muffins (Table III). Except for a minor contribution from flour, test fats were the only source of fat in the muffins. In the test diets, muffins provided 95% of the total fat, with the other 5% resulting from soybean oil included as a source of essential fatty acids. Calories TABLE I Percent Fatty Acid Composition of Medium-Chain Triglycerides Testeda Medium-Chain Triglyceride Fatty Acid CXb NBc DLd Caprylic acid 66.7 71.1 75.0 Capric acid 29.7 26.9 25.0 Other acids 3.6 2.0 0.0 'Based on suppliers' information. bCaptex 200 from Karlshamns, Columbus, OH. cNeobee M-5 from Stepan Co., Maywood, NJ. dDelios S from Henkel Corp., La Grange, IL. TABLE II Composition (%) of Air-Dried Muffins