Fats - Structure and Composition

What are Fats, Occurrence and Composition, Extraction, Role of Dietary Fats, Important functions in food, Structure of fatty acids, Major and Minor components in Fats.

1. Fats–structure & Composition Gopika M G S6 Int MSc Chemistry Amrita School of Arts and Sciences, Amritapuri Campus

2. Contents What are fats? Occurrence and Composition of fats Extraction Role of dietary fats in diet Important functions of fats in food Structure of fats Composition of fats

3. What are fats? Fats are substances that help the body use some vitamins and keep the skin healthy Th ey are also the main way the body stores energy. In food, there are many types of fats -- saturated, unsaturated, polyunsaturated, monounsaturated, and trans fats.  Examples include cholesterol, phospholipids, and triglycerides. Defenition: Fats are large molecules that are classified as lipids and are made up of glycerol and fatty acids.  

4. Occurrence and composition of fats Fats are the main constituents of the storage fat cells in animals and plants. They are one of the important food reserves of the organism. Chemically, fats are carboxylic esters derived from the single alcohol, HOCH2CHOHCH2OH, glycerol, and are known as Glycerides. More specifically, they are Triacylglycerides. Each fat is made up of many different carboxylic acids whose proportions varies from fat to fat.

5. Extraction Fats and oils are extracted from natural products by three operations; Rendering : Animal fats are generally separated from animal tissue by heating when the fat melts and flows down. Pressing : Oils are obtained from seeds by crushing between stell rollers and then pressed in a hydraulic press. Solvent Extraction : It is often applied to the residue after pressing or rendering for complete removal of oil or fat. The solvents used include petroleum ether and benzene.

6. Role of Dietary fats in diet Fats that we get from food are vital to good health. They provide energy and essential fatty acids for healthy Skin and important hormone – like substances. They also help to absorb fat soluble vitamins like A,D,E and K They are not just calorie powerhouse, but also serve many Chemical, Physical and Nutritional function in the food we eat.

7. Important functions of fats in food Fats can alter the food’s appearance by creating a glossy or moist visual texture. They are an important component in most emulsions. They have unique ability to absorb and preserve flavours. Fats provide one of the most efficient modes of heat transfer during cooking. The type of fat used in a particular product often determines the melting point of the final product. Fat is an effective method of delivering calories when needed, especially for delivering fat soluble vitamins like A,D,E,and K.

8. Structure of fats Fats are classified as  lipids , or a group of compounds which are substances made up of two or more elements that do not dissolve in water.  The fats are obtained by the esterification of Glycerol and Fatty acids. Glycerol Glycerol  is part of the structure of fat and is made up of three carbon atoms. Each carbon atom can bond, or attach, to four other atoms. One of those bonds is made with a hydroxyl-group, or a hydrogen and oxygen. The other three bonds are with carbon and hydrogen atoms. 

9. Fatty Acids They are made up of individual components called fatty acids. They are chains made of carbon and hydrogen atoms that have a carboxyl group at one end and a methyl group at the other. Carboxyl groups contain one carbon atom, one hydrogen atoms, and two oxygen atoms, and methyl groups include one carbon atom and three hydrogen atoms. The carbon atoms in the fatty acid molecules are linked by single or double bonds.

10. Fats and oils are called triglycerides (or  triacylcylgerols ) because they are esters composed of three fatty acid units joined to  glycerol , a trihydroxy alcohol: If all three OH groups on the glycerol molecule are esterified with the same fatty acid, the resulting ester is called a  simple triglyceride . Although simple triglycerides have been synthesized in the laboratory, they rarely occur in nature. I nstead, a typical triglyceride obtained from naturally occurring fats and oils contains two or three different fatty acid components and is thus termed a  mixed triglyceride .

11. Composition of Fats The main components of edible fats and oils are triglycerides. The minor components include mono- and diglycerides, free fatty acids, phosphatides, sterols, fat-soluble vitamins, tocopherols, pigments, waxes, and fatty alcohols.   Animal fats contain smaller amounts of minor components.

12. Major component Triglyceride A triglyceride is called a fat if it is a solid at 25°C; it is called an oil if it is a liquid at that temperature. These differences in melting points reflect differences in the degree of unsaturation and number of carbon atoms in the constituent fatty acids. Triglycerides obtained from animal sources are usually solids, while those of plant origin are generally oils. Therefore, we commonly speak of animal fats and vegetable oils.

13. A triglyceride consists of three fatty acids attached to one glycerol molecule. If all three fatty acids are identical, it is a simple triglyceride. The more common forms, however, are the "mixed" triglycerides in which two or three kinds of fatty acids are present in the molecule.

14. Terms such as  saturated fat  or  unsaturated oil  are often used to describe the fats or oils obtained from foods. Saturated fats contain a high proportion of saturated fatty acids, while unsaturated oils contain a high proportion of unsaturated fatty acids. The high consumption of saturated fats is a factor, along with the high consumption of cholesterol, in increased risks of heart disease.

15. Minor components Mono- and Diglycerides : Mono- and diglycerides are mono- and diesters of fatty acids and glycerol. They are used frequently in foods as emulsifiers. Free Fatty Acids : As the name suggests, free fatty acids are the unattached fatty acids present in a fat. Some unrefined oils may contain as much as several percent free fatty acids.  Phosphatides : Phosphatides, also known as phospholipids, consist of an alcohol (usually glycerol) combined with fatty acids, and a phosphate ester. Sterols : Sterols are found in both animal fats and vegetable oils, but there are substantial biological differences.  Tocopherols and Tocotrienols : Tocopherols and tocotrienols are important minor constituents of most vegetable fats. Pigments : Carotenoids are yellow to deep red color materials that occur naturally in fats and oils. Fatty Alcohols : Long chain alcohols are of little importance in most edible fats.

16. Fatty acids vary in Shape Unsactuated fatty acids form two different shapes.

17. Reference Organic Chemistry, Morrison & Boyd. LibreTexts: https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Book%3A_The_Basics_of_GOB_Chemistry_(Ball_et_al.)/17%3A_Lipids/17.2%3A_Fats_and_Oils Institute of Shortening and Edible Oils: http://iseo.org/FFO/page2.html