Fats and Oils Lecture 3 Student Notes PDF

Lecture 3 Fats and oils Fats and oils are both types of lipids, which are organic compounds composed of carbon, hydrogen, and oxygen atoms, they are essential components of our diet providing energy, insulation , and aiding in the absorption of fat soluble vit...

Lecture 3 Fats and oils Fats and oils are both types of lipids, which are organic compounds composed of carbon, hydrogen, and oxygen atoms, they are essential components of our diet providing energy, insulation , and aiding in the absorption of fat soluble vitamins. The primary difference between fats and oils lies in their physical state at room temperature: * Fats: Solid at room temperature. * Oils: Liquid at room temperature. Three major groups Triglycerides Phospholipids Sterols Chemical Structure: Both fats and oils are composed of triglycerides, which are molecules made up of three fatty acid chains attached to a glycerol molecule. The two are bonded with covalent bonds during condensation. The covalent bond that forms between glycerol and fatty acids is called the ester bond. The type of fatty acids determines whether a triglyceride is a fat or oil. Note: In lipids, fatty acids do not bond to one another but to glycerol only. 1 Formation of Trigylcerides (lipids) A triglyceride is formed by the condensation reaction between glycerol and 3 fatty acid molecules. The products are a triglyceride (containing 3 ester functional groups) and water. glycerol + fatty acids -----> triglyceride + water O H O H || | || H2O | HO -C- (CH2)nCH3 H- C - O- C -(CH2)n-CH3 H- C -OH O O | | || || + -----> + H2O H- C -OH HO -C- (CH2)nCH3 H- C - O- C -(CH2)n-CH3 | O | H- C -OH || O | || H- C - O- C -(CH2)n-CH3 H2O H HO -C- (CH2)nCH3 | H Types of Fatty Acids: Fatty acids saturated Unsaturated monounsaturate polyunsaturated d * Saturated Fats: Have no double bonds between their carbon atoms. These are typically solid at room temperature and are found in animal products like meat, butter, and cheese, as well as in some plant-based foods like coconut oil and palm oil. While they are a source of energy, consuming too much saturated fat can raise bad cholesterol levels, increasing the risk of heart disease. 2 * Unsaturated Fatty Acids: Have one or more double bonds between their carbon atoms. They are typically liquid at room temperature and are found in plant oils like olive oil and vegetable oil and are considered healthier than saturated fats. * Monounsaturated Fatty Acids: Have one double bond. Found in olive oil, avocados, nuts, and seeds, they help lower bad cholesterol and raise good cholesterol levels. * Polyunsaturated Fatty Acids: Have two or more double bonds. Found in fatty fish like salmon and mackerel, as well as in vegetable oils like sunflower and corn oil, they help reduce inflammation and lower the risk of heart disease. 3 Functions of Fats and Oils: The Role of Fats and Oils in Our Bodies: * Energy Storage: Fats and oils are a concentrated source of energy, providing 9 calories per gram. * Insulation: They help maintain body temperature by insulating our organs. * Protection: They protect vital organs from injury. * Vitamin Absorption: They aid in the absorption of fat-soluble vitamins (A, D, E, and K). * Cell Structure: They are essential components of cell membranes. * Hormone Production: They are used to produce hormones like estrogen and testosterone. It's important to include healthy fats and oils in our diet, such as those found in olive oil, avocados, nuts, seeds, and fatty fish, while limiting saturated and trans fats. * Trans Fats: These are formed through a process called hydrogenation, which converts liquid oils into solid fats. They are found in processed foods like margarine, baked goods, and fried foods. Tran’s fats significantly raise bad cholesterol levels and lower good cholesterol levels, increasing the risk of heart disease and stroke. It's best to avoid trans fats altogether. Chemistry of fats: Unsaturated fats can be hardened by reducing the proportion of unsaturated fatty acids, principally oleic acid. Oils may be hardened by hydrogenating the oleic acid, and converting it to stearic acid. 4 CH3(CH2)7 CH = CH(CH2)7CO2H ---H2---- →→ CH3(CH2)16CO2H (stearic acid) oleic acid nickel catalyst The nickel catalyst,, is added to the oil at about 180 °C. The oil is stirred and the hydrogen bubbled through. After hydrogenation the oil is separated from the catalyst by filtration. In addition to hardening the oil, hydrogenation increases its stability. The degree of unsaturation is measured by the iodine value of the oil. When iodine is added to a triglyceride, formed from an unsaturated fatty acid, it reacts with the double bonds in the molecule. The degree of unsaturation may be calculated from the amount of iodine absorbed: CH3(CH2)7CH= CH(CH2)7CO2H + I2  CH3(CH2)7 CHI- CHI(CH2)7CO2H (oleic acid) One molecule of iodine is used to saturate each double bond. The result is expressed as the iodine value, which is the number of grams of iodine required to saturate 100 g of oil. Essential fatty acid: Fatty acids which are polyunsaturated and cannot be synthesized by the body and must be present in the diet, are called essential fatty acids. e.g. lenoleic, lenolenic, and arachidonic acids. Omega 3 fatty acids: A type of essential fatty acids is Ѡ-3 fatty acids which are a family of unsaturated Fatty acid. Polyunsaturated fatty acids with double bond between 3 rd and 4th carbon from the left on the structure. 5 Examples of Ѡ-3 fatty acids include: Linolenic acid and Arachidonic acids. Oils containing Ѡ-3 fatty acids reduced the heart disease and help lowering the cholesterol levels in the blood. Fatty Fish that have pink or red flesh are higher in omega-3 FA than fish with white flesh. Tuna, Salmon, and sardines are good sources. Omega 6 fatty acids: Linoleic acid (lin-oh-LEE-ik) is the only ‘essential’ omega 6 fatty acid. The body cannot produce the amount of omega 3 and 6 you need to survive, Linoleic acid is necessary for normal growth and development, and is found in vegetables, grains, nuts, seeds, , olive, and corn oil, garlic, and soybeans Phospholipids: Found in food in relatively small amounts Like triglycerides, phospholipids are lipids built of fatty acids and glycerol. However, phospholipids are composed of two, not three, fatty acids. Like in triglycerides, these fatty acids can be saturated and unsaturated. One of the three fatty acids that attach to glycerol is replaced with a phosphate- containing group. Similarities and differences between phospholipids and triglycerides:  Phospholipids and triglycerides have fatty acids and glycerol.  Both phospholipids and triglycerides contain ester bonds (between glycerol and fatty acid).  Both phospholipids and triglycerides may have saturated or unsaturated fatty acids. 6   Both phospholipids and triglycerides are insoluble in water.  Function as emulsifiers: o One side of molecule attracts fat o One side attracts water  i.e. Lecithin Sterols: Cholesterol  Widely known sterol  Found ONLY in animal foods  Is associated with coronary heart disease  Our bodies also make cholesterol Plant sterols Phytosterols Interfere with absorption of cholesterol Fat in Food Preparation: Tenderizing in baked foods Contribute to leavening Creaming of fat and sugar Promote moistness Major components of salad dressings May be heated to high temperatures Frying of foods Contribute flavor Butter 7  Protein Proteins are present in all living plant and animal tissues. Composition: Proteins, like fats and carbohydrates, contain carbon, hydrogen and oxygen. In addition they contain about sixteen per cent nitrogen, which distinguishes the proteins from carbohydrates and fats. Proteins are more complex and larger molecules than carbohydrates and fats. Some proteins contain sulphur, phosphorus, iron or other minerals also. Proteins are built from simpler compounds called amino acids. The amino acids contain a basic (amino — NH2 ) and an acidic (carboxy1 — COOH) group in their molecules as indicated below: The R may be a hydrogen atom or a more complex group, giving rise to variety of about 23 or more amino acids present in plant and animal proteins. Some of these amino acids cannot be synthesized in the body, but are essential for maintenance in human beings. These amino acids, which have to be supplied in the food are called essential amino acids (Eight amino acids needed by adults are—isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine (ILLMPTTV). One additional one needed by growing children is histidine). The remaining amino acids, which can be synthesized from others in the body, are termed as non-essential 8 amino acids, because our body does not have to depend for their supply on the foods we eat. Structure of Proteins: The structure of a protein molecule is dependent on the number and kind of amino acids present in it. The sequence of amino acids and the manner in which these are linked indicates the structure of the protein. Primary: Long chains Secondary: Spring like coiling - Alpha helix Tertiary: Folding of coils forming globular shape Quaternary : Combining of globular proteins Protein Quality: Amino acids used as building blocks for proteins Nine amino acids are essential for adult human nutrition Complete proteins include essential amino acids 9  Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Histidine Biological Value of Protein is a measure of its quality or ability to support life. If a protein contains all the essential amino acids in the proportions needed by the body, it is said to have a high biological value. If a protein lacks sufficient amount of one or more essential amino acids, it is by itself unable to support life and is said to be of low biological value. Thus, biological value indicates the relative nutritional value of a protein. Food proteins vary greatly in their amino acid composition. For example, animal foods such as milk, eggs, fish, poultry etc., contain all essential amino acids. But cereals are low in lysine and most pulses are low in methionine. However as cereals and pulses are normally consumed together with other foods such as vegetables, milk or curd, the lack in one food is supplemented by the other foods. In other words, various foods, when eaten together in a meal, complement each other and the biological value of protein mixture in the meal is much higher than that of the individual food proteins, when eaten separately. Properties of Proteins: Proteins are synthesized from amino acids, which contain a basic and an acidic group. The presence of these basic and acidic groups in the constituent amino acids of 10 proteins is responsible for their amphoteric nature. The ability of proteins to act as an acid or a base is referred to as its amphoteric nature. The amphoteric nature of proteins is very important from biological point of view, as it prevents sudden change of pH in the body. In food mixtures, these groups help to bind ions and change the texture, volume and appearance of the product. Denaturation : When proteins are exposed to heat, light and/or change in pH, structural changes occur. These changes in structure of proteins are known as denaturation. Denaturation leads to change in solubility of proteins. It may be reversible, if conditions which cause it are mild, but mostly the changes which occur are irreversible. Coagulation : Proteins coagulate on exposure to heat and/or change of pH. All proteins are first denatured and then coagulated by heat. The coagulation occurs between 65° and 90°C. Coagulation means curdling, formation of a mass, thickening or solidifying. For example, when egg is boiled or scrambled, the egg proteins coagulate and a solid mass is formed from raw egg, which is a fluid. When milk is incubated with curd, the liquid milk is transformed to curd, due to coagulation of milk protein by the lactic acid formed. The temperature of coagulation increases with addition of other ingredients. For example, when milk and sugar are added to egg to prepare egg custard, the coagulation temperature increases to 85° to 90°C, from 65° to 70°C, which is the temperature of coagulation of egg proteins. If coagulation is gradual, as in the preparation of curd, the proteins bind water and hold it. This property of proteins is known as hydration. When proteins are coagulated by the action of acid on hot milk, the protein (casein) coagulates and whey is formed. The liquid is known as whey and the coagulum as cottage cheese or paneer. 11 Thus the nature of the product of coagulation is dependent on the agent used for coagulation, the intensity and period of exposure to heat. If coagulated protein is heated for a long period, it becomes tough and dry. Roasted meat, if heated at high temperature to doneness, is dry and tough to chew. Therefore, to obtain an acceptable product, it is important to monitor the time and temperature while preparing these protein foods. Hydration of Proteins: Proteins can form hydrates with water. This reaction is very important in food science. The protein molecule contains a number of groups, which contain a pair of unshared electrons and are therefore capable of attracting and binding the hydrogen of a molecule of water. The water molecule which has been bound attracts another molecule of water, and thus aggregates of water can build up around each polar group on the protein molecule. The extent of hydration of protein dispersion depends on concentration of protein, the pH, the temperature and the presence of other substances, which combine with water. Gelatin when placed in cold water swells, due to hydration. If it is heated, it dissolves. When cooled, it solidifies again. Thus the water is held in the network of swollen gelatin particles. Gelatin is useful as a gelling agent, a whipping agent in foam and as clearing agent in fruit juices, due to this property. Emulsifying Agent : Emulsion is dispersion of one liquid in another liquid. An emulsion is a heterogeneous system made up of two phases. A substance which stabilizes an emulsion is known as an emulsifying agent. If oil and water are shaken vigorously, the two liquids are dispersed to form an emulsion. Such an emulsion is unstable, and in order to stabilize it, a third substance, called an emulsifying agent or emulsifier, must be added. Emulsifying agents are substances whose molecules contain both hydrophilic (water-loving) and hydrophobic (water-hating) groups. 12 Proteins act as emulsifying agents, because of their amphoteric nature. For example, in preparation of mayonnaise, eggs act as emulsifying agent. Foaming Agent: Formation of foam is necessary in some food preparations. Proteins when beaten are able to hold in air, and thus improve the texture and feel of the food. Ice-cream and lemon meringue are excellent examples of this property. Gel Formation: Gel formation is a very important process in food science. The changes that occur in food preparation such as stiffening of an egg, meat and milk cookery depends on gel formation. A gel displays the property of rigidity. A classic example is that of gelatin gel, which forms with as low a concentration as one per cent. When colloidal dispersions of large molecules are cooled, the viscosity increases and the mass attains some rigidity. This point is called gel point. Egg custard, gelatin gel, puddings etc., are excellent examples of these phenomena. Food Sources: Plants are the primary source of proteins, as they synthesize protein by combining nitrogen and water from soil with carbon dioxide from the air. All animals and fish depend on plants to provide them proteins. Pulses, nuts, oilseeds, milk and milk products, eggs, fish, poultry and meat are the good sources of protein in the diet. Cereals and their products provide 50 to 70 per cent of proteins in the Indian dietary. Functions: The principle functions of proteins in the body are as follows: 1. Building new tissues in growth stages of life, from conception up to adulthood, and after injury. 2. Maintenance of tissues already built and replacement of regular losses. 13 3. As regulatory substances for internal water and acid base balance. 4. Formation of enzymes, antibodies, some hormones and one of the B-vitamins. 5. Formation of milk. 6. Energy supply. Each gramme of protein supplies four calories to the body. Deficiency: ?????????????? 14