Fats are an important organic compounds in living organisms. they are insoluble in water and soluble in organic solvents. Carbon, hydrogen and oxygen make up the fats where the oxygen content is low, and carbon and hydrogen content is high. They contain more heat than sugar and responsible for storing energy for living organisms.
Oils and fats are the most common lipids in daily life and are also known as triglycerides. They are composed of one molecule glycerol and three molecules fatty acids. Each of three carbons of glycerol has a hydroxyl group. There is a carboxyl group in one end of fatty acid, and the rest is hydrocarbon chain. These hydroxyl groups react with the carboxyl groups of fatty acids to produce ester bonds that hold them together. These three fatty acid molecules are identical or dissimilar. Each chain has 16-18 carbon atoms.
Saturated and Unsaturated Fat
Fats are classified into saturated and unsaturated fats according to whether they contain carbon-carbon double bond. If their hydrocarbon chains do not contain a double bond, or if they have as many hydrogen atoms as possible on their carbon chain, then they are called saturated fat. These straight molecules of saturated fat can be tightly bound, so they have a relatively high melting point and are solid at room temperature, such as animal fats: lard or butter. Some plants are also rich in saturated fats, such as coconut and palm.
If their hydrocarbon chain contain double bonds, or the hydrogen atoms are not saturated, then they are called unsaturated fat. The hydrocarbon chains of fatty acids are bent or kinked due to double bonds, preventing they from being closely aligned, so they have a lower melting point and are liquid at room temperature, such as vegetable oils and fish fats.
Fatty acids that contain a carbon-carbon double bond are called monounsaturated fatty acids. The fats produced by their esterification are monounsaturated fats. Olive, avocado, sunflower and canola oils are rich in monounsaturated fatty acids.
Fatty acids containing multiple carbon-carbon double bonds are known as polyunsaturated fatty acids. They are esterified to produce polyunsaturated fats. They have more bends making them more loosely arranged resulting in a lower melting point. The body cannot synthesize unsaturated fatty acids with multiple double bonds; they must be consumed from food. Corn, soy, safflower oil and deep-sea fish are rich in polyunsaturated fatty acids.
Fat and Health
Fats have a small proportion of oxygen and a large proportion of carbon and hydrogen (single bonds of carbon and hydrogen contain more energy), so they can create more calories when fully oxidized, a little more than twice as much energy as sugars. Saturated fats store slightly more calories than unsaturated fats. The unstable double bond of unsaturated fats can be easily oxidized, so they can react with some strong oxidants, for example, to destroy free radicals in the body. Their antioxidant properties make them a good dietary supplement. Long-term intake of unsaturated fats can prevent high blood pressure, diabetes, heart disease and fight against aging. Foods rich in unsaturated fatty acids include peanuts, sesame seeds, salmon and tuna.
However, excessive fat intake can lead to serious health problems, including an increased risk of heart disease, obesity, high blood pressure, diabetes and certain cancers. To prevent these diseases, WHO recommends that total daily fat should only be 15 to 30% of total energy intake. For example, for an adult with about 2,000 kcal daily energy, only 300 to 600 kcal energy intake should come from fat (about 33 to 67 g).