Medium-chain triglyceride (MCT) as a unique oil, its research began in the 1950s. It is generally believed that MCT is a triglyceride composed of fatty acids with 6 to 12 carbon atoms. The fatty acids that constitute MCT are called medium-chain fatty acids (MCFA). These MCFAs can interact with glycerides without a catalyst. The formation of MCT.
Due to the short carbon chain of medium-chain triglycerides, it can be used as an emulsifier in the food industry and has good mutual solubility and solubility between the water phase and the oil phase. Because MCFA or MCT is different from the special physiological and biochemical properties of long-chain fatty acids (LCFA) or long-chain triglyceride (LCT), they have long been used in human clinical treatment (such as Gastroenteritis, obesity, diabetes), especially to provide energy for patients with lipodystrophy and premature babies. In recent years, medium-chain triglycerides have been widely used in sports foods as a functional raw material for rapid energy replenishment.
1 The physical and chemical properties of medium-chain triglycerides
MCT is only composed of saturated fatty acids, has a low freezing point, is liquid at room temperature, and has a low viscosity. Compared with soybean oil, it is a completely odorless, colorless, and transparent liquid. Compared with ordinary fats and hydrogenated fats, the content of medium-chain triglyceride unsaturated fatty acids is extremely low, the oxidation stability is very good, and its iodine value does not exceed 0.5.
MCT is particularly stable at high and low temperatures. After a long time of frying, ordinary vegetable oil thickens due to polymerization reaction, and its transparency is reduced, while MCT has only a slight increase in viscosity, which is roughly equivalent to unused refined vegetable oil. Even at 0°C, MCT is still a clear and transparent liquid with low viscosity. In addition, MCT has good mutual solubility with various solvents, oils, some antioxidants, and vitamins. In addition, MCT has better ductility and lubricity than other vegetable oils.
MCFA also has some properties that are different from LCFA:
- The melting point of MCFA is generally lower than that of LCFA, and it is liquid at room temperature. This is conducive to the digestion and utilization of animals because the melting point of fatty acids or fats is negatively correlated with their digestibility in the body within a certain range.
- Because MCFA has a relatively small molecular weight and is a weak electrolyte, it can be ionized relatively at a neutral pH, so they are relatively soluble in water. Generally, fatty acids with higher polarity and water solubility are digested, absorbed, and transported faster in the body.
- MCFA is also volatile, while LCFA does not. Therefore, MCFA or MCT has the characteristics of the short carbon chain, small molecule, high polarity, and high water solubility. These properties are closely related to their digestion, absorption, transportation, and metabolism processes in animals.
2 Metabolic characteristics
In addition to the above-mentioned differences in physical and chemical properties, MCT has two fundamental differences from LCT.
First, there are different metabolic pathways in the human body. The metabolism of MCT in the body is similar to that of carbohydrates, but it does not require carnitine to shuttle, so it is not regulated by the metabolic mechanism of adequate carbohydrate and protein intake. LCT is first hydrolyzed in the intestine, then re-esterified into triglycerides, and then combined with proteins and phospholipids to form chylomicrons. Then it is absorbed through the intestinal wall, and finally enters the lymphatic system and later the blood circulatory system, thereby dispersing into the cells. In addition, LCT eventually becomes adipose tissue in the body, which is stored in the body for future energy needs. On the other hand, MCT is directly transported to the liver through the portal vein, where it is broken down to produce energy, and it hardly becomes adipose tissue and is stored in the body.
Second, the energy supplied by LCT is 9 calories/g calories, while the energy supplied by MCT is 8.3 calories/g calories, which is lower than LCT, but it is more than twice the energy supplied by glucose. MCT generally takes only 30 minutes to reach the blood from the intestinal hydrolysis and absorption, 2.5 hours to reach the peak, and LCT to reach the peak in 5 hours. If LCT or cholesterol are taken at the same time, MCT can inhibit their absorption in the intestine. MCT can enhance the absorption of calcium, magnesium, and amino acids. Studies have shown that the daily dietary MCT content can be tolerated up to 100 g, such as 40% of the total calorie intake of MCT, there are no side effects.
3 Synthesis method of MCT
At present, there are three synthetic methods for MCT.
The first is the hydrolysis esterification method. This method is to hydrolyze coconut oil, palm kernel oil, or Litsea cubeba oil to obtain medium chain fatty acids (MFAT for short), then esterify them with glycerin and refine them to obtain MCT. This is the commonly used method at present. This method has the disadvantages of a long time, difficult separation of by-products, and high energy consumption, but the MCT produced has high purity.
The second is the alcoholysis of acid chloride. In this method, the coconut oil is firstly hydrolyzed and rectified to obtain medium-carbon chain fatty acids, and then the medium-carbon chain fatty acids are reacted with PX3, PX5, or SOCL2 to obtain acid chloride, and then the acid chloride and glycerol are subjected to alcoholysis to obtain MCT. This method consumes less energy and takes a short time, but the process route is long and the pollution is heavy.
The third is the enzymatic method. It uses a special lipase to carry out the hydrolysis of oil esters and the esterification between glycerol and fatty acids to prepare MCT. The principle is that lipase will promote the hydrolysis of glycerides under conditions of sufficient moisture, and will promote the synthesis of triglycerides under conditions of limited moisture. The advantage of this method is that the quality of the MCT produced is better and the color is lighter, but the intermediate layer is difficult to handle, takes a long time, and requires high-temperature resistant lipase.
4 Application of medium chain triglycerides
4.1 Application in infant food
Due to the low activity of lipoprotein lipase and liver lipase in infants and young children, the level of carnitine is also low, which can easily cause fat deposition in the organs. Medium-chain triglycerides can be rapidly absorbed in the duodenum, and its absorption does not depend on the activity of esterase and bile acid. In the liver, the transport of medium-chain triglycerides does not depend on the carnitine transport system. In addition, it can also improve the absorption of minerals and some essential fatty acids. Therefore, medium-chain triglycerides, as a substance that provides energy quickly, have a very good role in promoting the growth and development of infants whose digestive system functions are not yet fully developed, especially premature infants and weak infants.
4.2 Application in sports food
In the liver, the transport of medium-chain triglycerides does not depend on the carnitine transport system, so it can quickly increase energy and improve athletes’ endurance. At the same time, it can also reduce the rate of catabolism and save protein consumption. Medium-chain triglycerides can provide 8.3kcal of energy per g, which is twice that of carbohydrates. A large number of studies have shown that medium-chain triglycerides can improve the endurance level of athletes, accelerate fatigue recovery, save protein consumption and increase the proportion of lean body mass. Therefore, it can be used for nutrient supply and fatigue recovery for intense sports and physical labor.
4.3 Application in diet food
Compared with standard oils, medium-chain triglycerides provide less energy per g (8.3kcal/9kcal). At the same time, it can also improve satiety. Medium-chain triglycerides are generally only used as energy sources and will not be stored in adipose tissue. It can also reduce the degradation of muscle protein. Because it has a unique metabolic pathway, it can increase energy consumption. In addition, it can also improve the absorption of minerals and some essential fatty acids.
Therefore, most of the MCT acts as an oxidative energy supply in the human body and is almost not stored as fat in the human body, which is beneficial to the weight loss of obese patients. MCT has been used as a fat substitute and has a wide range of applications in cakes, ice cream, and chocolate.
4.4 Application in patient food
MCT is not only easy to digest and absorb in the human body, but also clears faster in the blood. Therefore, MCT is very suitable as special food for patients with post-operation, infection and skin burns. MCT can also be used in foods for those suffering from fat malabsorption, AIDS and cancer. In addition, MCT has no adverse effects on blood glucose and insulin concentration, so it is also suitable for use in foods for diabetic patients.
4.5 Application in other food industries
In the food additive industry, MCT can be used as a solvent and carrier for edible flavors and pigments. In the processing of baked goods, medium-chain triglycerides are often combined with cheap vegetable oils to act as anti-sticking agents to prevent baked goods from sticking to pans or molds. Pure medium-chain triglycerides or mixed oils with vegetable oils are also often used as lubricants and mold release agents for sausage compression molding.
MCT can also be used to treat various fat-soluble vitamins, pigments, and antioxidants. When a small amount of MCT is added, the viscosity of high-viscosity fatty substances will be greatly reduced. In the food processing industry, MCT is also used to replace easily oxidized milk fat to make milk dessert wine and cheese imitation products. If used in combination with water-soluble colloids, MCT can also be used as a clouding agent for beverages. In addition, MCT can be used as a lubricant for food processing machinery instead of mineral oil.
