Food Chemistry PDF

FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 1 Copyright Disclaimer Copyright © 2024 by Swa Education All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical reviews and certain other non- commercial uses permitted by copyright law. For permission requests, write to the publisher, addressed “Attention: Permissions Coordinator,” at the address below: Publisher Detail Barawan Kala, Mall Road, IIM Road, Lucknow, 226101 +91 8601635179 [email protected] E- mail: [email protected] FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 2 TABLE OF CONTENTS S. No CHAPTER NAME PAGE No. 1 CARBOHYDRATE 05-17 2 PROTEIN 18-22 3 LIPID 23-28 4 VITAMIN 29-38 5 MINERAL 39-46 6 PIGMENTS & COLOURS 47-52 7 FLAVOURS 53-55 8 ENZYME 56-66 09 ANTINUTRITIONAL FACTOR 67-78 FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 3 FOOD CHEMISTRY E-Book FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 4 CHAPTER- 01 CARBOHYDRATE FOOD CHEMISTRY Food: Anything solid or liquid which when swallowed, digested and assimilated, and nourishes the body. Any substance whether processed, partially processed, or Unprocessed, which is intended for human consumption. Food chemistry: Discipline that is involved in investigating the composition structure and properties of food stuffs and their components. CARBOHYDRATES INTRODUCTION Carbohydrates are primary products of photosynthesis. Carbohydrates are polyhydroxy aldehydes or ketones and their derivatives. General formula CX(H2O)Y Provide 4kcalg-1 of energy. Ideally carbohydrate should supply 60-70% of total calories required. Prefix related to source followed by Suffix “ose” e.g. fructose (fruit sugar), maltose (malt sugar), lactose (milk sugar), xylose (wood sugar) cellulose (carbohydrates from cell membrane) CLASSIFICATION 1. MONOSACCHARIDE: Cannot be hydrolysed into simple carbohydrates. Aldoses: -CHO group is present at C1 Ketoses: -C=O group is present at C2 Crystalline in nature Water soluble Mostly have sweet taste. The alpha and beta sugars are also known as anomers. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 5 Concept of nomenclature For aldehydes and ketones, the simplest monosaccharide have three carbon atoms. ISOMERISM Imaging the 3d structure of glyceraldehyde there are two possibili[es D configuration: -OH carried by the asymmetric carbon is situated to the right of the plane formed by the carbon chain. L configuration: OH is situated to the left of this plane. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 6 Example of aldopentose Hexoses The chemical formula of all hexoses is C6H12O6 Glucose, Mannose, Galactose are aldohexose. Fructose is a ketohexose. Conversion of linier sugar into cyclic form When the linier model of aldohexose/ketohexose is built, the oxygen atom on the fourth and fifth carbon atoms can be turned to approach within the bonding distance C one. In such an event the hydroxyl group on C4 or C5 of the sugar molecule can form cyclic hemiacetals. If the ring closes by the parting of the hydroxyl on C4, a five membered heterocyclic ring called “furanose” is formed. If the ring closes by the participation of the C5 hydroxyl, a six membered “pyranose” is formed. Forma6on of the Pyranose ring (glucopyranose) FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 7 Forma6on of the Furanose Ring α – D fructo-furanose Monosaccharide deriva6ves Amino sugars: Hydroxyl group in sugar is replaced by amino group. Common amino sugars are glucosamine and galactosamine. Deoxy sugars: In these sugar derivatives one oxygen atom is removed at a designated carbon atom. 2, deoxy ribose is a constituent of DNA. 2. OLIGOSACCHARIDES Composed of 2- 10 monosaccharide units. We have to study about disaccharides and tri saccharides and tetra saccharides in detail. Joining of monosaccharide is a dehydration synthesis reaction via glycosidic bond to form oligosaccharides. A glycosidic bond is covalent bond, joins a carbohydrate with another group which may or may not be a carbohydrate. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 8 Oligosaccharides can be further classiﬁed on the basis of number of monosaccharide units formed on hydrolysis. 1. Disaccharides: 2 monosaccharide units combined by glycosidic linkage. General formula Cn(H2O)n-1 example: C12(H2O)11 i.e. sucrose a) Maltose: contains two glucose units via α 1,4 glycosidic linkage, on hydrolysis it produces 2 molecules of α d glucose. Can be seen in many germinating seeds where starch is being broken down. b) Lactose: Contains ꞵ-d Galactose and ꞵ-d Glucose joined together by ꞵ-1,4 glycosidic linkage. 2. Trisaccharides: Composed of three monosaccharides with two glycosidic bonds connecting them. Raffinose: In this structure glucose acts a monosaccharide bridge between the galactose and fructose. Galactose and glucose is bonded with α 1,6 glycosidic linkage and fructose is bonded with glucose via ꞵ -1,2 glycosidic linkage. On hydrolysis, produces d galactose and sucrose. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 9 3. Tetrasaccharides: Composed of four monosaccharides with three glycosidic bonds. Stachyose: it is composed of two units of α, d galactose, one unit of α, d glucose and one unit of ꞵ-d fructose. Disaccharide Unit 1 Unit 1 bond Maltose Glucose Glucose α 1,4 Lactose Glucose Galactose ꞵ 1,4 Sucrose Glucose Fructose α (1,2) ꞵ Trisaccharide Unit 1 Bond Unit 2 Bond Unit 3 Raffinose Galactose α (1,6) Glucose ꞵ (1,2) Fructose Tetra-saccharide Unit 1 Unit 2 Unit 3 Unit 4 Stachyose Galactose Galactose Glucose Fructose FuncIon of sugars in food Apart from nutri[onal value, sugars have other func[ons in food, they act as: Humectants (compound which absorb moisture from air), Plasticizers (decrease brittleness) Texturing agents Flavour producing agents Sweeteners The sweetness of sugar depends upon their ability to form hydrogen bonds with water, with other polar compounds and among themselves. Browning ReacUons (non-enzymaUc browning) Non enzyma[c browning reac[ons are responsible for the colour and ﬂavour of foods, such as dates, honey and chocolate. Dis[nc[ve ﬂavours that coﬀee beans, ground nuts, cashew nuts and breakfast cereals develop aier roas[ng is due to browning reac[ons. The presence of reac[ve reducing sugars FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 10 is responsible for browning in foods. On hea[ng they undergo ring opening, dehydra[on and fragmenta[on. The unsaturated carbonyl compounds that are formed react to produce brown polymers and ﬂavour compounds. The heat induced browning reac[on occur in two ways; Caremeliza[on and the Maillard reac[on. CaremelizaUon: It is the process of browning of sugar used extensively in cooking resul[ng in sweet, nuky ﬂavour and brown colour. As the process occurs, the volatile chemicals such as diacetyles are released, producing the characteristic caramel flavour. Caremelization is a pyrolytic reaction (thermal decomposition of material at elevated temperature. It involves high temperature appx above 1650 C. It involves removal of water and breakdown of sugar. When caremelization involves the disaccharide sucrose, it is broken down into monosaccharide glucose and fructose. Factors that increase the rate of reaction are acid or base catalysed at pH above 9 or below 3. Three types of polymers are formed; Caramelans, Caramelenes and Caramelins. Maillard reacUon: In this reac[on the reducing sugar reacts with amino acid by impact of heat to produce complex brown coloured compound. Reducing sugars: Carbohydrates with presence of free aldehyde or ketonic groups; e.g: all monosaccharides and some disaccharides. This reaction takes place at temperature between 1400 C to 1650 C. The sugar amines form a brown colour at a lower temperature than that of formation of colour by caramelization, hence maillard reaction products predominate in browned foods. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 11 Mechanism of Maillard reac6on: Step 1. Carbonyl group of sugar reacts with amino group of the amino acids to give N subs[tuted glycosylamine with the release of water. Step 2. The unstable glycosylamine undergoes Amadori rearrangement to form stable ketosamines. Step 3. Melanoids are formed, the brown to black, amorphous unsaturated heterogeneous polymers are called “melanoids”, these are responsible for speciﬁc colour and aroma of the food. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 12 CARAMELIZATION MAILLARD REACTION Reaction takes place only by involving Reaction takes place between reducing sugars in food. sugars and amino acids present in food It is a pyrolytic reaction it is a non pyrolytic reaction. Takes place above 1650 C Takes place at around 140 to 1650 C Formation of three polymers responsible for brown Formation of melanoids. colour of food; Caramelans, Caramelenes, Caramelins. Example: caramel candies, caramel sauce, cola Example: toasting of bread, crust of roast products. pork. 3. POLYSACCHARIDES Poly means ‘many’ and saccharide means ‘sugar’, so polysaccharides contains many sugar molecules. The generic name of polysaccharides is glycans. Repeated units of monosaccharides or their derivatives, held together by glycosidic bonds. Linier as well as branched polymers. Two types: 1. Homo-polysaccharide 2. Hetero-polysaccharide. Proper6es of polysaccharides: Not sweet in taste Many are insoluble in water Hydrophobic in nature They are high molecular weight compound Can be extracted to form a white powder Inside the cell they are osmotically inactive, its large size prevents it from leaving cell, so it can be easily stored inside the cell. They consist of hydrogen, carbon and oxygen. The hydrogen to oxygen ratio being 2:1. Types of polysaccharides: 1. Homo-polysaccharides: Contains the same type of monosaccharide Some important homo- polysaccharides are: i. Glycogen: Storage polysaccharide in animals, hence sometimes called animal starch. This is mainly present in liver and skeletal muscles. It is a branched chain polysaccharide. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 13 ii. Inulin: It is made up of number of fructo furanose molecules linked together in chains. It is found in tubers of dahlia, artichoke etc. iii. Cellulose: makes up more than 25% of cell wall in higher plants. accounts for nearly half of worlds supply of carbon. Insoluble in water, and not digested by human so act as roughage or dietary fibre. It can be broken down to glucose by certain microbial enzymes, this is the way cellulose is hydrolysed in the rumen of animals to provide them with sugar. Avicel (a partially hydrolysed cellulose) is added to food to contribute bulk without calories. Carboxymethyl cellulose (CMC) is used in the manufacture of ice cream, retards enlargement of ice crystals during storage. iv. Starch: It is a principal stored food reserve polysaccharide of the plant. Starch provides the major source of energy in the diet of humans. Starch is composed of d glucose units held by glycosidic bonds. It is also known as glucosan or glucan. Starch consists of two polysaccharide components: a. Amylose b. Amylopectin Cereal starches usually contain 25% amylose and 75% amylopectin. a. Amylose: It is a straight chain polymer of d glucose units. Constitutes 20% of starch. It is not truly soluble in water but forms hydrated micelles. It contains α 1,4 glycosidic bonds between two glucose units. Waxy or glutinous starch like waxy corn starch contains little or no amylose. It is responsible for blue colour produced by iodine with starch. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 14 b. Amylopectin: It is a branched chain polymer of d glucose units Constitutes 80% of starch It is insoluble in water It contains α 1,4 glycosidic bonds between two glucose units in the straight chain and α 1,6 glycosidic bonds at the branching. It is responsible for waxy properties of starch but it does not contribute to gel formatio AMYLOSE AMYLOPECTIN Linier chain polymer made from Branched chain polymer of d several d glucose units. glucose units. Amylose contribute for 20% of starch Amylopectin contribute for 80% of starch. α 1,4 glycosidic linkage Contains both α 1,4 and α 1,6 glycosidic linkage. Stains black or dark blue when iodine is Stains reddish brown when iodine is added. added Responsible for gel formation Responsible for waxy properties of starch. ProperUes of starch: Granular structure: starch occurs as granule in cytoplasm of the cell. Granule remain essentially intact during most type of processing, such as milling, separation, and purification of starch. Gelatinization: process of breaking down of intramolecular bonds of starch molecules in the presence of water and heat, allowing hydrogen bonding sites to engage more water. This irreversibly dissolves the starch granules in water. It results in thickening and formation of gel. The temperature at which granules begin to swell rapidly is called gelatinization temperature. Retrogradation: It is opposite of gelatinization, here disaggregated amylose and amylopectin chains in a gelatinized starch paste re associate to form more ordered structure. It occurs when gelatinized starch is cooled for long period of time e.g. bread staling. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 15 Modified starches: also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch to change its properties. These are used in food products as thickening agents, stabilizer, emulsifier etc. 2. Hetero-polysaccharides: Composed of repea[ng units of diﬀerent monosaccharides and their deriva[ves, e.g. pec[ns, gums, agar. a. Pectins: Composed of galactose, arabinose and galacturonic acid residues. They are used for the preparation of jellies in food industries Used as dietary fibres. They are useful in reducing blood glucose levels and lowering plasma cholesterol levels. Sources are: apple, carrots and citrus fruits. The water insoluble parent pectic substance that occur in plants is protopectin, this in fruits decreases during ripening and soluble pectin increases. Protopectin on restricted hydrolysis, gives pectinic acid and pectin. b. Gums: These are hydrophilic substances that give a viscous solution or dispersion when treated with hot or cold water and can form gels and mucilages. Gums are incorporated to improve texture, water retention, and rehydration of many dehydrated, frozen and instant convenient foods The seed gums commonly used are guar gum obtained from a common Indian pulse ‘guar’ (Cyamopsis tetragolonaba) and ‘locust bean gum’ obtained from locust bean. These are long chain polysaccharide of mannose and galactose. These gives colloidal dispersion of high viscosity which are stable over the pH range of foods and are not affected by heat processing, freezing, acids salts or protein in the food product. Gums act as stabilizer, clarifying agent, thickeners in different food products. c. Agar: It is an extract from red and brown algae. It is a polymer of sulphated galactose and glucose molecules. Agar is used as dietary fibre (roughage). Since it is not digested by humans, it is used to relieve constipation. Agar is the main components of medium used in the bacterial culture since bacteria do not digest it. Agar forms the strongest and most stable gels at lowest concentration, therefore agar finds several uses in stabilizing food products. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 16 d. Carageenans: These are also sulphated galactans from seaweed extract. There are both gel forming and non-gel forming carrageenan fractions. Both form stable complexes with protein and other gums. Carageenans are specially, useful in dairy products because they form stabilizing complexes with milk proteins and give more acceptable texture to processed cheese and cream. e. Algin: It is a product obtained from brown algae. Composed of mannuronic acid and galacturonic acid. When the carboxyl group is neutralised by various neutral cation, the product is called alginate. alginate gives widely variable sols and viscosity properties in acid and salt solution. Some microbial gums also find use in foods. Two important ones are dextran and xanthan gums. f. Dextran: Is formed by the action of Leuconostoc mesenteroids on sucrose. It is a polysaccharide consisting of d glucose units. g. Xanthans: Formed by action of xanthomonas on d glucose. The gum contains glucose, mannose and galacturonic acid and are of high molecular weight. It dissolves in water and find use in food as stabilizer, emulsifier, thickener, suspending agent etc. Some other important carbohydrates: Dextrin: These are products of par[al breakdown of starches. Dextrins are intermediate in size between starches and sugars and exhibit proper[es that are intermediate between these classes of materials. These are formed when starch is subjected to dry heat. The toas[ng of bread converts a part of starch to dextrin. The sweet taste of toast is due to this change. Hemicellulose: Insoluble polysaccharide in water but unlike cellulose are soluble in alkali. Composed of pentoses, hexuronic acid and rhamnose. Hemicellulose help cement together closely packed cellulose microﬁlaments. Together with cellulose, hemicellulose forms a por[on of undigested carbohydrate and is therefore a dietary ﬁbre. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 17 CHAPTER- 02 PROTEINS Proteins: These macromolecules made up of 20 different amino acids They are hydrolysed to form amino acids. These amino acids are structural units of protein. Amino acid contains both a basic amino group and an acidic carboxyl group attached to the same carbon atom, the α carbon. In additionally they also posses a third group referred to as the side chain denoted by R. Structure of proteins: The hydroly[c process takes place during diges[on by proteoly[c enzymes. Protein PolypepUde PepUde Amino acids A. Primary structure: It is sequence of a chain of amino acids linked together. The di-functionality of these groups allows the individual amino acids to join in long chains forming peptide bonds. Peptide bond: bond formed between amino group (NH2) of one amino acid to carboxyl group (COOH) of the other amino acid. Dipeptide bond: is two amino acids joined by a peptide bond, like wise oligopeptide refers to a chain of 3-10 amino acids. Polypeptide bond: The sequence formed by more than 10 amino acids. Each amino acid has both one letter and three letter abbreviation, commonly used to simplify the written sequence of a peptide or protein. example: Alanine (Ala)/A, Arginine (Arg)/R, Glutamic acid (Glu)/E FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 18 The amino acid sequence of a protein is encoded in DNA, proteins are synthesized by a series of steps called transcription (the use of a DNA strand to make a complimentary messenger RNA strand- mRNA) and translation (the mRNA sequence is used as a template to guide the synthesis of the chain of amino acids which make up protein). B. Secondary structure: Strands of proteins or pep[des have dis[nct characteris[c local structural conﬁrma[ons or secondary structure, dependent on hydrogen bonding. The two main type of secondary structure are α helix and ꞵ sheet. 1. α-helix: Is a right handed coiled strand. The side chain substituents of the amino acid groups extend to the outside. Hydrogen bonds formed between the oxygen of the C=O of each peptide bond in the strand and the hydrogen of N-H group of peptide bond form amino acids below it in the helix. The hydrogen bond make this structure stable. The side chain substituents of the amino acids fit in beside the N-H groups. 2. ꞵ-sheet: The hydrogen bonding in ꞵ-sheet is between adjacent strands rather than within the strand. The sheet confirmation consists of pairs of strands lying side by side. The carbonyl oxygen in one strand makes hydrogen bond with the amino hydrogen of adjacent strands. The two strands can either be parallel or anti-parallel depending on whether the strand directions (N terminus to C terminus) are the same or opposite, the antiparallel ꞵ-sheet is more stable due to more well aligned hydrogen bonds. C. Tertiary structure: The overall three dimensional shape of an entire protein molecule is the tertiary structure. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 19 The protein molecules will bend and twist in such a way as to achieve maximum stability or lowest energy state. Although a three-dimensional shape of a protein may seem irregular and random, it is fashioned by many stabilizing forces due to bonding interaction between the side chain group of amino acids. D. Quaternary structure: The three level of structural organiza[on discussed so far apply to all proteins with a single polypep[de chain. When a protein contains two or more polypep[de chains, the structure formed is k/a quaternary structure. These chains may or may not be iden[cal but in both cases they are linked by weak bonds. Haemoglobin was the ﬁrst protein for which a complete quaternary structure was determined. ClassiﬁcaIon of proteins: 1. Based on chemical composition Protein Characteristic Example/ Occurance Globular Albumins Soluble in water, dilute salt solution, dilute acid and Lactalbumin, egg albumin, base, coagulated by heat serum albumin Globulins Soluble in salt solution, insoluble in water Serum globulin, arachin and conarchin of peanuts, myosin Histones Basic proteins, soluble in most common solvents Nucleoproteins Fibrous/ scleroproteins Collagens Resistant to digestive enzymes, insoluble Skin, tendons, bones Elastins Partially resistant to digestive enzymes Arteries, tendons, elastic tissues Keratin Highly insoluble and resistant to digestive enzymes Skin, hair, nails FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 20 2. Classiﬁca6on based on conﬁrma6on: 1) Simple proteins: which yield only amino acid on hydrolysis. E.g. albumin, globulin, prolamine etc. 2) Conjugated protein: these are madeup of simple protein (apoprotein) & non protein substance k/a prosthe[c group. They yield not only amino acids but also other organic or inorganic compounds. E.g. nucleoprotein, glycoprotein, phosphoprotein, lipoprotein, metalloproteins. 3) Derived proteins: these are formed from simple and conjugated protein and are the degrada[on product obtained by the ac[on of acids, alkalis or enzymes on proteins. E.g. denatured proteins, peptones, polypep[des. 3. Classiﬁca6on based on their R group or side group: i. Acidic amino acid: contains more carboxyl group than amino group. E.g. aspartic acid, glutamic acid. ii. Basic amino acids: contains more amino group than carboxyl group. E.g. lysine, glutamine, histidine. iii. Neutral amino acid: equal number of amino and carboxyl group. E.g. glycine, alanine, serine iv. Aromatic amino acids: contains aromatic group (ring form). E.g. phenylalanine, tyrosine, tryptophan. v. Sulphur containing amino acids: contains sulphur e.g. methionine, cysteine. 4. Classiﬁca6on based on func6on: Protein can be classiﬁed according to their biological role as: Enzymes: hexokinase, lactate dehydrogenase, DNA polymerase. Contractile proteins: myosin, actin, flagellar proteins Storage proteins: casein, ovalbumin, ferritin, zein Transport protein: haemoglobin, myoglobin, serum albumin Protective proteins: antibodies, thrombin. Hormones: insulin, growth hormone Structural proteins: glycoproteins, collagen, elastin, fibroin Genetic proteins: nucleoproteins, histone DenaturaIon of Protein: Denatura[on is a process in which a protein loses its na[ve shape due to the disrup[on of weak chemical bonds and interac[ons thereby becoming biologically inac[ve. It leads to loss of physical, chemical and structural proper[es of proteins. Mechanism: Unfolding of native protein occurs by different physical and chemical agents Higher temperature- heat denaturation, thermal denaturation Lower temperature- cold denaturation In both the cases there is breakage of hydrogen bonds, disulphide bonds, hydrophobic interactions, but there is no breakage of peptide bonds during denaturation. Causes of denaturation: heat, violent shaking or agitation, hydrostatic pressure, UV radiation, acid and alkalis, organic solvents etc. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 21 CoagulaUon: Denatura[on can result in coagula[on, which is the clotng or curdling of protein molecules into a rela[vely insoluble protein mass. Factors aﬀecUng coagulaUon: Acid: denatura[on occurs more readily under acidic condi[on. Mechanical ac[on, sugar (delays coagula[on), salt(promote), addi[on of rennin(promote) Example: egg white turns from transparent to white colour. Nature of food proteins: Animal proteins: Meat: edible muscle of cattle, sheep and swine. Contains about 20-25 % protein on wet basis. Fish: contains about 10-21% of protein. Egg: 13-14% protein egg white contains major portion of protein (ovalbumin), yolk is a mixture of lipoprotein and phosphoprotein. Milk: cow milk contains about 3.5% protein (casein and whey proteins). Casein accounts for 80% and whey protein 20% of total milk protein. Plant protein: Vegetable protein contains 1-6% protein, cereal grains 7-15%, pulses contain more than 20% protein. Non-tradiUonal proteins: Due to need of increased production of protein microbes are used. They grow rapidly, yield is high and their growing condition can be controlled, these are used to obtain single celled protein. Two species of yeast, Candida utilis (torula yeast) and saccharomyces carlsbergenesis (brewers yeast) have been used for human food. These contain appx 50% of protein on dry basis. Two genera of algae- Chlorella (green algae) and spirulina (blue green algae) when grown under controlled condition, contain 50-60% protein on dry weight basis. Apart from this, fungi and plant leaf protein are also used to extract protein now a days. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 22 CHAPTER- 03 LIPID Lipid Term lipid is used to denote diverse type of compounds which are insoluble in water but soluble in non-polar solvents, such as chloroform, carbon disulphide, benzene and ether. Proper6es of Lipids They are organic compounds formed of fats and oils. Lipids produce high energy and perform diﬀerent func[ons within a living organism, such as: Lipids are generally hydrophobic, meaning they repel water and do not dissolve in it. Fats and oils, in the form of triglycerides, are efficient energy storage molecules, providing a concentrated source of energy when broken down. Phospholipids are essential components of cell membranes, forming the lipid bilayer that defines cellular boundaries. They help in the selective permeability of a cell membrane. Lipids like cholesterol and steroid hormones consists of four-ring structure and function in membrane fluidity and cellular signalling. Lipids provide essential fatty acids that the body cannot produce on its own and allow the absorption of fat-soluble vitamins. Types of Lipids Lipids are mainly classiﬁed into three types. They are simple, compound, and derived lipids. 1. Simple Lipids: FA+Alcohol. Simple lipids are triglycerides, esters of fatty acids, and wax esters. The hydrolysis of these lipids gives glycerol and fatty acids. 2. Compound Lipids: FA+ Alcohol+ additional group Complex or compound lipids are the esters of fatty acids with groups along with alcohol and fatty acids. Examples are Phospholipids and Glycolipids. 3. Derived lipids: Hydrolysis of simple/compound lipids Derived lipids are the hydrolyzed compounds of simple and complex lipids. Examples are fatty acids, steroids, fatty aldehydes, ketone bodies, lipid-soluble vitamins, and hormones. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 23 1. SIMPLE LIPIDS Esters of faFy acid with various alcohols. Simple lipids are classiﬁed into Triglycerides and Waxes. A. Triglycerides/ triacylglycerol They consist of glycerol molecules linked to three fatty acid chains through ester bonds. Triglycerides are found in adipose tissue (body fat) and serve as a long-term energy reserve. They are the constituents of fats and oils. Fats are those lipids that are solid at room temperature, and Oils are those lipids that are liquid at room temperature. i. Fatty acids: these are long hydrocarbon chains with a methyl group at one end of the chain and a carboxylic acid group at other. Most natural fatty acid contains even number of carbon atoms in the chain. Depending on the degree of unsaturation they are: a. Saturated fatty acid: These fatty acid have all the hydrogen atom it can hold. They have a linier shape and there are no double bonds between carbon atoms. They contain only single carbon to carbon bond. E.g. butyric acid, lauric acid, caproic acid, stearic acid FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 24 b. Unsaturated fatty acid: If some of the hydrogen atoms are missing and have been replaced by double bond between carbon atoms then the fatty acid is said to be unsaturated. Generally, these are liquid at room temperature. E.g. linoleic acid, arachidonic acid, linolenic acid. c. Monounsaturated fatty acid: If there is one double bond, the fatty acid is said to be monounsaturated fatty acid. E.g. Oleic acid. d. Polyunsaturated fatty acid: If there is more than one double bond, then the fatty acid is known as PUFA. In these fatty acids the hydrogen atom can be arranged in one of two ways, they represent the different isomeric structure of fatty acids. E.g. linolenic acid, arachidonic acid, linoleic acid. Cis form: The hydrogen atoms are attached to the carbon atom of the double bond. Hydrogen atoms are located on the same side of the double bond. Trans form: The hydrogen atoms are located on the opposite sides of the double bond, across from one another. All naturally occurring fats and oils that are used in foods exists in the cis conﬁgura[on. Hydrogena[on of oil causes conversion of double bonds to trans conﬁgura[on. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 25 B. Waxes: ester of long chain acid with long chain alcohol. Animal wax (beewax), plant wax (carnauba wax). Waxes are found on surface of plant and tissues. 2. COMPOUND LIPIDS: Esters of faky acid containing groups of phosphorus, carbohydrate or protein present in an addi[on to alcohol and faky acids. Phospholipid: Contains only two fatty acid acidified to glycerol, in place of third fatty acid there is phosphoric acid and nitrogen containing group. E.g. lecithin (egg yolk). Glycolipids: Contains fatty acid, carbohydrate and nitrogenous base. They have carbohydrate components within their structure like phospholipid. They are generally not a major component of food lipids. Lipoprotein: Macromolecular complex of lipid with proteins. Found in mammalian plasma bound with protein. 3. DERIVED LIPIDS: When both simple and compound lipids combine and undergo the process of hydrolysis, derived lipids are produced. They are derivatives of lipid or lipid like substances like: Carotenes: in plants they function as accessory pigments e.g. carrot. In animals these are converted to vitamin A (forms visual pigment rhodopsin). Sterols: they are amphipathic lipids due to presence of both polar and non polar group. Lipid soluble vitamins: Vit A, Vit D, VitE, VitK. Reac6ons of fats: Stability of fat is important to maintain fresh taste or odour during storage and use. Fats with substantial unsaturation in fatty acid are usually unstable. Agents causing oxidation: pro-oxidants Agent preventing oxidation: antioxidants Rancidity: Complete or incomplete oxidaUon or hydrolysis of fat and oil when exposed to air, light moisture or by bacterial acUon,resulUng in unpleasant taste and odour. Three pathways for rancidity: 1. Hydrolytic 2. Oxidative 3. Microbial 1. Hydrolytic rancidity: Triglycerides are hydrolysed and free fatty acid are released. This reaction of lipid with water may require a catalyst (acid, base enzymes or thermal effects) leading to formation of free fatty acid and glycerol. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 26 When a base act as hydrolysing agent, the liberated fatty acids are converted into their salt or soaps, and this kind of hydrolysis is termed as saponification. 2. Oxidative rancidity: it is associated with the degradation of oxygen in the air. The double bond of unsaturated fatty acid cleaves by free radical reaction involving molecular oxygen. Mechanism of oxidative rancidity: oxidation occurs through a free radicle chain reaction involving three stages: a) Initiation: formation of free radicle b) Propagation: free radicle chain reaction c) Termination: formation of non radicle products. a) Initiation: unsaturated hydrocarbon loses a hydrogen atom to form a radical. (radical: it is an atom molecule or ion that has an unpaired electron). RH———> R*+H* b) Propagation: In this stage, the oxygen present in the atmosphere gives rise to the peroxides. These peroxides then react more and more with the unsaturated fatty acids and then produce new radicals. R*+ O2———> ROO* (peroxide) c) Termination: In the third stage, two radicals combine together to form a new single bond. ROO* + ROO* ⇒ ROOR + O2 (End Products) The product formed are very highly reacNve molecules which are responsible for unpleasant smell and bad taste of lipid. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 27 3. Microbial Rancidity Microbial Rancidity occurs when microorganisms such as molds or bacteria use their enzymes like lipases to break down chemical structures of fat in oil-producing unwanted smell and taste. This process can be reduced by inhibiting microorganisms or by destroying them. It can also be reduced by pasteurization and the addition of antioxidants, AnUoxidants: substances added to lipid or lipid containing food to retard oxida[ve breakdown of fat and thus prevent spoilage of food. An[oxidant work by combining with free radical and thus interrup[ng the free radical chain mechanism. E.g. Ascorbic acid(Vitamin C), Tocopherol (Vitamin E). HydrogenaUon of oil: To treat with H2 and catalyst to decrease double bond and increase single bond. Mechanism of hydrogenaUon: In the presence of catalysts nickel pla[num or palladium the hydrogen atom combines to the unsaturated faky acid conver[ng it to unsaturated form. ReacUon result: Saturation of double bond Trans fatty acid formation Advantage of hydrogenaUon: Hydrogenated oil are more stable than unsaturated oil. They are cheap substitute of saturated fats from animal origin such as lard or butter. Melting point is increased and the state of oil is changed from liquid to solid at room temperature. E.g. Vegetable ghee FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 28 CHAPTER- 04 VITAMINS Vitamins Vitamins are low molecular weight organic substances necessary in small amounts in the diet of higher animals for normal growth, maintenance of health and reproduction. C Funk first discovered vitamins in 1912. All animals need vitamins but every vitamin is not required by all, e.g. human beings and guinea pigs get scurvy when fed diets that do not provide Vit C, but dogs, cats, rats and many other species make this vitamin in their bodies and do not need it in their food. Plants and microorganisms synthesize vitamins. ClassiﬁcaUon: Based on their solubility in water or fats 1. The fat soluble vitamins A D E and K are found in food in complex association with lipids. 2. The water soluble vitamins are B complex vitamins and vitamin C. The B complex consists of several unrelated compounds, containing nitrogen as a part of their chemical structure. As the chemical identity of different chemicals was established, chemical names have replaced original names. Trick: W.B.C : Water soluble Vit B and Vit C Vitamin A,D,E,K are fat soluble vitamins. Vitamins Chemical name Soluble in Vit A Retinol र Fat Vit B1 Thiamine थ Water Vit C Ascorbic acid ए Water Vit D Calciferol क Fat Vit E Tocopherol टॉ Fat Vit K Phylloquinone फ़ी Fat FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 29 Func4ons Vitamins have diﬀerent func8on in various animal species. They regulate metabolism, help convert fats and carbohydrates into energy and assist in forming bones and teeth. Vitamin form coenzyme part of many enzymes. Excess water soluble vitamins are excreted mainly in urine but excess of fat soluble vitamins will result in storage and this could be toxic. DistribuUon in foods: Vitamins are present in variety of natural foods. Green leafy vegetables, pulses nuts and cereal grains are good source of most of the vitamins. The vitamin content of fruit and vegetable depends upon variety, growing conditions, and several other factors. Animal foods like milk, eggs or meat are good sources of water soluble vitamins, except vitamin C. Loss of Vitamins: loss is due to processing i.e. trimming, removal of skins and peels of fruits and vegetables results in loss of vitamins, e.g. Vit C is lost in the case of apple and pineapple and B3 in case of carrot in this way. Vitamin present in seed coat and germs of cereals are lost during milling. Water soluble vitamins are lost during heating and blanching. High temperature used for short time processing and added chemicals have detrimental effect on content of certain vitamins. Vitamin losses also occur during storage. To restore vitamins, fortification and enrichment are done. A. Fat soluble Vitamins: These are generally associated with fatty foods, such as butter, cream, vegetable oils and fats of meat and fish. Fat soluble vitamin do not contains nitrogen in their structure. They are more stable to heat than the B vitamins, and are less likely to be lost during cooking and processing of foods. They are absorbed from the intestine along with fats and lipid in food. As stated earlier they are not excreted in urine and get stored in the body to a considerable extent, and this can result in toxicity. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 30 1. Vitamin A: Vit A is an alcohol, it has been named “Retinol” because of its specific function in retina of the eye. Metabolically active forms of vitamin A include the corresponding aldehyde (retinal) and the acid (retinoic acid). Carotenoids (Provitamin A) are unsaturated hydrocarbons, a number of structurally related carotenes (α,ꞵ,γ carotenes) and cryptoxanthin occur widely distributed in nature. ꞵ carotene has symmetrical structure and the molecule splits into half to give two molecules of vitamin A. Vit A is fairly stable to heat, but prolonged heating in contact with air destroys it. It is easily destroyed by oxidation and U.V. light. Antioxidants prevent loss of vitamin A by oxidation. FuncUons: Vitamin A is essential for night vision. The retina is the layer of light sensitive cells, lining the back inside of the eye, consisting of rods and cones. Cones respond to light by day and rods by night. Rods contain the photosensitive pigment rhodopsin (visual purple).The pigment is composed of protein called opsin bonded to a molecule called retinal. The pigment is photosensitive. when there is deficiency of Vitamin A the rods cannot adjust to light changes, resulting in night blindness. One of the chief functions of vitamin A is to maintain the health of epithelial cells, skin as well as glands and their ducts, Vit A helps these cells to produce mucous. When Vit A is not present, it leads to keratinization of mucous membranes, this renders the protective barrier role played by these membranes in protecting the body against infection, that’s why Vit A is also known as anti-infective vitamin. Deﬁciency disorders: Prolonged deﬁciency of Vit A may produce skin changes, night blindness and corneal ulcera8on. In extreme deficiency, the mucous membrane of the respiratory GI tract and urinary tract do not function normally and are less of a defence against infecting organisms. Night blindness: It is attributed to the functional failure of the retina in the proper regeneration of visual purple (rhodopsin). Xeropthalmia: Vit A deficiency can lead to keratinization of the cornea, resulting in xeropthalmia. This is an important cause of blindness in poorly fed childrens in developing countries like India. Xeroderma: Vit A deficiency results in the skin becoming dry, scaly, and rough. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 31 2. Vitamin D: Calciferol Vitamin D is represented by Ergocalciferol (Vit D2) and Cholecalciferol (Vit D3). i. Ergosterol: It is a plant sterol. By the action of U.V. radiation ergosterol is converted into ergocalciferol (Vit D2). ii. 7- dehydrocholesterol: It is an animal sterol. By the action of U.V. radiation it is converted into Cholecalciferol (Vit D3). Vitamin D is remarkably stable and prepara8ons of food containing it can be warmed or kept for long periods without its deteriora8on. Storage processing and cooking do not aﬀect its ac8vity. FuncUons: like other fat soluble vitamins, Vitamin D can be stored in the body to a large extent. It promotes growth and proper mineralization of the bones and teeth. Vit D increases intestinal absorption of calcium, phosphate transport in intestine, maintains proper calcium and phosphorus levels in serum and increases the reabsorption of calcium by kidney. Deﬁciency: Rickets: the deficiency of Vitamin D in children during the period of active skeletal growth causes rickets, which results from the defective mineralization of the ends of growing bones. As a result the ends remain abnormally pliable and eventually assume a bent form resulting in bowlegs, enlargement of bones around the joints and narrow distorted chest with beading of the ribs. Osteomalacia: deficiency of Vit D in adults. Osteomalacia leads to defective mineralization. In this case there is decalcification of bone shafts and the tendency is for fractures rather than bending. 3. Vitamin E:Tocopherol It is the most widely available vitamin in common foods. Wheat germ oil is the richest source of the vitamin. It is also present in other cereals, green plants, egg yolk, milk fat, butter, meat, nuts and vegetable oils. α-tocopherol is the most active form of Vitamin E. The most important chemical property of vitamin E is its antioxidant property, Vit E serves to prevent the formation of peroxides from polyunsaturated fatty acids, thus preventing the oxidation of unsaturated fats. FuncUon: Protect the cell membranes from deterioration caused by peroxides and free radicals formed from fats. This ability of Vit E to protect membranes has been related to ageing, which is also characterised by cell membrane deterioration. Deﬁciency: 1. Early ageing 2. Fragility of red blood cells 3. 3.Muscle damage. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 32 Compared with Vit A and Vit D, Vit E is relatively non toxic. However it is suggested that high levels of Vit E might interfere with Vit K activity in some individuals. About 80% or more of activity is lost when whole wheat is converted to white bread. Dehydration of food leads to decrease in Vit E activity, because of their higher chances to undergo oxidation. 4. Vitamin K: Two forms of vitamin K occur naturally Vit K1 (Phylloquinone) in green plants, and Vit K2 (Menaquinone) which is formed as a result of bacterial action in the intestinal tract. The sources of Vit K are cereals, dairy products and vegetables. Half of the Vit K in man is of intestinal origin synthesized by gut flora and half is phylloquinone. Vit K is an anti haemorrhagic vitamin. It is necessary for the synthesis of prothrombin and other proteins involved in the clotting of blood. Deﬁciency: Deficiency of Vit K is uncommon in adults, new born infants before establishment of intestinal flora show a deficiency. Prolonged blood clotting time which may lead to internal haemorrhage and uncontrolled bleeding. B. Water soluble vitamins: Water soluble vitamins are not stored to any extent in the body and the ingested vitamin in excess of requirement is excreted through the kidney. For the body to carry out normal functions, the daily supply of these vitamins is necessary. Some Vitamins of the B group results from the bacterial activity in small intestine. Many are used as food additives. These vitamins are extensively lost by leaching during the cooking operations. 1. B Complex Vitamins: One important reason for grouping the B vitamins together is that they all occur together in nature. In general B group vitamins function as coenzymes and thus they play an essential role in the metabolic processes of all living cells. VITAMIN CHEMICAL NAME B1 THIAMINE B2 RIBOFLAVIN B3 NIACIN B5 PANTOTHENIC ACID FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 33 B6 PYRIDOXINE B7 BIOTIN B9 FOLIC ACID B12 COBALAMINE i. Thiamine (Vitamin B1): Thiamine is readily soluble in water and insoluble in fat solvents. Thiamine is one of the least stable vitamins. The dry vitamin is fairly stable but solution form is unstable in the presence of heat and alkali. Freezing has little or no effect on thiamine content of food. Temperature is an important factor in thiamine stability. Thermal destruction of thiamine results in many degradation products and leads to the formation of a characteristic odour which is involved in the development of ‘meaty’ flavour in cooked foods. Thermal destruction is pH dependent. Starch/Protein component of cereal products exert a protective action against the destruction of the vitamins in some pH ranges. Thiamine is also destroyed by oxidation and reduction. It is particularly sensitive to sulphur dioxide and sulphite, and so these should not be used to preserve thiamine containing foods. FuncUons: The most important func8on of thiamine is its role as a coenzyme, it combines with phosphoric acid to form thiamine pyrophosphate (TPP) which func8ons as a coenzyme. Deﬁciency: Mild thiamine deﬁciency may result in fa8gue, emo8onal instability, depression, irritability, retarded normal growth, loss of appe8te. Beri-beri: Severe thiamine deﬁciency of long dura8on causes beriberi which is characterized by disturbances of neurological and cardiovascular symptoms and gastro intes8nal tract. Individuals consuming large amount of tea and alcohol may have increased risk of thiamine deﬁciency, because it alters the absorp8on of this vitamin. ii. Riboﬂavin (vitamin B2): This vitamin is widely distributed in plant and animal foods in small amounts. Rela8vely good dietary source are milk, cheese, liver, eggs, and leafy vegetables. Dried yeast is also a rich source of the vitamin, pulses and lean meat contain appreciable amount of riboﬂavin. Riboflavin belongs to a group of yellow fluorescent pigments called flavins. Riboflavin is orange yellow in colour. On reduction it changes into a colourless form. It is less soluble than thiamine but is more stable to heat in acid and neutral media. It is destroyed by heating in alkaline solution, baking soda used for faster cooking destroys much of the riboflavin content of the food. On exposure to light, riboflavin readily loses its vitamin activity. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 34 Function: Free riboflavin must be phosphorylated in the intestinal tract before it can be absorbed. On combining with phosphoric acid, it becomes part of the structure of the two Flavin coenzymes: FMN (Flavin mononucleotide) and FAD (Flavin adenine dinucleotide), these catalyse many oxidation and reduction reactions in the cells. Deﬁciency: Cheilosis: reddened denuded areas on the lips, with cracks at the corners of the mouth. Glostitis: swollen and reddened tongue. Scaly, greasy dermatitis on the face, ears and other parts of the body. Eye disorders: itching, burning, lacrimation, cataract. iii. Niacin: (VitaminB3) The term niacin includes both nicotinic acid and nicotinamide, both natural forms of vitamin with niacin activity. Niacin can be synthesized by the bacteria of the intestinal flora and is formed in the tissues from the amino acid tryptophan, e.g. milk and egg, have a far greater niacin potency. Niacin is one of the most stable vitamins being relatively resistant to heat, light, acids and alkalis. FuncUons: Form the active part of coenzymes that play an important part in biological oxidation. Nicotinamide is the component of two coenzymes- Nicotinamide adenine dinucleotide (NAD), and nicotinamide adenine dinucleotide phosphate (NADP). Deﬁciency: Weakness, indiges8on, ulcerated mouth and tongue. Pellagra: caused due to prolonged deﬁciency of niacin. This results in Diarrhoea, demen8a (depression) and derma88s. Skin lesions are aggravated by exposure to sunlight, neurological symptoms and mental changes occur in more advanced cases. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 35 iv. Pantothenic acid: Vitamin B5 It is widely distributed in foods and is particularly abundant in animal tissues, whole grain cereals and pulses. It also occurs in lesser amount in milk vegetables and fruits. It is reported to be synthesised by intestinal microflora. Pantothenic acid is more stable in solution than in the dry form. It is stable in pH range 4-7. It is decomposed by alkali and dry heat. It is stable in moist heat in neutral solutions. FuncUon: Component of coenzyme A, which is involved in reac8ons which play important role in release of energy from carbohydrates and glucose synthesis. Deﬁciency: Burning feet syndrome: burning sensation and numbness in feet. Pain and sensation in arms and legs, loss of appetite, nausea, and indigestion. Pulse rise, fainting attacks, and increase in susceptibility to infection have also been observed. v. Pyridoxine: (Vitamin B6) There are three chemical compounds found in foods which have Vit B6 activity, they are pyridoxine, pyridoxal, pyridoxamine. Pyridoxine (pyridoxol) is the most stable form of this vitamin and is the form used for the fortification of foods. The vitamin is stable in acidic medium and relatively stable in alkaline solution. It is very unstable to light, the product formed by photo conversion is biologically inactive. This vitamin is widely distributed throughout the plant and animal kingdoms. The best source are meat, specially liver, some vegetables and grain cereals with bran. FuncUon: Pyridoxine is found in cells in active form, pyridoxal phosphate (PLP). This is the coenzyme of many enzymes involved in carbohydrate, fat and protein metabolism. This vitamin is the cofactor of enzymes involved in the conversion of tryptophan to niacin, and release of glucose from glycogen. Deﬁciency: Depression, confusion and convulsions. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 36 vi. BioUn: (Vitamin B7) Biotin is water soluble sulphur containing vitamin. It is stable to heat and light but unstable in strong acid and alkali. Its optimum stability is in pH range 5-8. As it contains a Sulphur atom it is susceptible to oxidation. Good source include liver, kidney, egg yolk, groundnuts and some vegetables. FuncUon: Biotin is a coenzyme required by several carboxylating enzymes which have the capacity to add or remove carbon dioxide. The vitamin plays a very important role in the metabolism of both carbohydrate and fats. Deﬁciency: hair loss, scaly skin, weak and brimle nails. vii. Folic acid: Vitamin B9 The name folic acid comes from latin word foliage or leaf (folium) because the vitamin was first isolated from spinach leaves and was known to be widely distributed in green leafy plants. Yeast, kidney, liver and green leafy vegetables specially, spinach, asparagus and broccoli, are rich sources of folic acid. Dried beans and whole wheat bread are good sources of the vitamin. Loss of folic acid occurs when foods are processed and stored vitamin activity is lost in processed and stored milks. Primarily the inactivation is due to oxidation. FuncUon: Aoer absorp8on, folic acid is converted into many ac8ve coenzyme forms, many of them are essen8al for the synthesis of nucleic acid and for normal metabolism of certain amino acids, this explains the important role of folate in cell division and protein synthesis. Deﬁciency: Megaloblastic anaemia, poor growth and other blood disorders. GI tract disturbances arising from impaired absorption. Folate controls macrocytic anaemia during pregnancy. viii. Cobalamine: Vitamin B12 It is known by the name cobalamine since it is found as a coordina8on complex with cobalt. The cobalt present in the vitamin molecules occupies the centre of the molecule and may be amached to various chemical groups.When amached to cyanide group the chemical is called cyanocobalamin (more stable) and when amached to the hydroxyl group, hydroxycobalamine. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 37 Vitamin B12 is only found in animal foods. liver and kidney are excellent sources of this vitamin. Milk, muscle meat, cheese eggs and sea foods are good sources of this vitamin. Human requirements are very low, and this is met by intestinal bacterial synthesis. The coenzyme part of vitamin B12 is major part of vitamin, present in food is very unstable to the heat used in processing. About 10% of the vitamin is lost when milk is pasteurized. FuncUon: Cobalamine is necessary for normal func8oning in the metabolism of all cells, specially, for those of GI tract, bone marrow, nervous 8ssue and for growth. Deﬁciency: Not usually dietary in origin, but results due to lack of its absorption in intestine. Pernicious anaemia: it is an autoimmune condition that prevents your body from absorbing Vit B12. A special protein called intrinsic factor (IF), binds vitamin B12 so that it can be absorbed in the intestine, this protein is released by the cells in the stomach. When the stomach does not make enough intrinsic factor, the intestine cannot properly absorb Vit B12. 2. Ascorbic acid: Vitamin C Ascorbic acid is a highly soluble compound that has both acidic and strong reducing proper8es. It is the most unstable of all known vitamins, in solu8on it easily gets oxidized specially, on exposure to heat. Oxida8on is accelerated in the presence of copper and alkaline pH. Excellent sources are citrus fruits, berries, guava, capsicum and green leafy vegetables. FuncUons: Helps in healing of wound, fractures, bleeding gums and reduces liability to infections. The absorption of iron is increased by dietary ascorbic acid when the two nutrients are ingested simultaneously. Large doses of ascorbic acid have generally been considered as non toxic. Deﬁciency: Scurvy: When deprived of dietary Vitamin C for longer 8me, scurvy is caused. Its symptoms are weakness, pale skin, poor appe8te, swollen gums, loosening of teeth and bone joint diseases. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 38 CHAPTER- 05 MINERALS Minerals: These are inorganic components of food that leave ash as residue when burnt. They occur in foods and tissues as inorganic salts (sodium chloride, Calcium phosphate) in combination with organic compounds (phosphoproteins, phospholipids, haemoglobins and chiefly in their ionic forms Na+ K+ Ca2+ Cl- and H2PO4-. Minerals have various functions in the body: About 4-6% of human body weight consists of minerals, 80% of total mineral is the skeleton and rest in other organs. As ions in body fluids, minerals regulate the metabolism of many enzymes, maintain the acid base balance and osmotic pressure, facilitate the membrane transport of essential compounds, and maintain nerve and muscular irritability. However trace elements are toxic when consumed in excessive amounts. Depending upon their amounts in the adult’s body, the minerals are classified as: 1. Macrominerals: Required in the adult human body in amounts of over 100mg per day. These include Calcium, Phosphorus, Sulphur, Potassium, Chlorine, Sodium & Magnesium. 2. Microminerals (trace minerals): Required in amounts of less than 20mg per day and they are Iron, Fluorine, Zinc,Copper, Iodine,Chromium & Cobalt. 1. Macronutrients A. Calcium: It is the most abundant mineral in the body. The body of and adult male weighing 70kg contains approximately 1200 gm of calcium which comprises 39% of total minerals present in the body. About 99% of calcium is present in skeleton. In the bones Calcium occurs as calcium phosphate. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 39 About 1% of the body’s calcium is found in the body fluids and soft tissues, this calcium is mostly in the ionic form, this is essential for certain enzyme activities, blood clotting & muscle contraction. Usually 20-30% of ingested calcium is absorbed by the body. The calcium phosphorus level influence the absorption of Ca+2. Vitamin D, low pH, lactose, low fat, high protein increase Ca+2 absorption. Oxalic acid in some fruits and vegetables, phytic acid present in cereals, alkaline medium and emotional instability decreases absorption of calcium. Among common foods, milk and milk products are the richest source of calcium. The calcium in milk is assimilated readily because of the lactose and vitamin D. Other foods rich in calcium are molasses, nuts, sesame seeds and millets (ragi). Deﬁciency: Rickets in children and osteomalacia in adults. Osteoporosis: Sometimes there is gradual demineralization of bony tissues: this disease is characterized by porosity, thinness, and fragility of the bones, this is due to decreased calcium absorption in bones. B. Phosphorus: Second to calcium in abundance, it comprises 22% of the total minerals of the body. About 80% of phosphorus is present as calcium phosphate in the bones, the remaining 20% is present as blood and other cells as soluble phosphate ions and also in lipids, proteins and carbohydrates, phosphorus is component of nucleic acids and cell membranes. Rich source of phosphorus in food are meat, poultry, fish, egg, milk, nuts and pulses. Phosphorus is nearly present in all foods and dietary deficiency is very rare. Phosphorus deficiency when it occurs, results in weakness, anorexia, and pain in the bones. C. Sulphur: While other minerals take care of dietary needs in inorganic forms, sulphur is required principally in the form of the sulphur containing amino acids, cysteine and methionine. Sulphur is present in all protein but is more prevalent in the keratin of skin and hair. Sulphur is also a component of vitamins thiamine and biotin. Sources are Egg, garlic, onions and broccoli. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 40 Deﬁciency: Can cause severe arthriUs symptoms, acne, briale nails and hair. D. Magnesium: It is component of chlorophyll and is absolutely essential for plants to synthesise carbohydrates. The human body contains 20-28 g of magnesium, more than half of which is stored in the bones. Essential part of enzyme involved in the liberation of energy. Magnesium is important in maintaining the electrical potential of nerve and muscle membranes. Magnesium occurs widely in foods, particularly those of vegetable origin. Deﬁciency: Magnesium deficiency is important complication in kwashiorkor, hypertension, coronary heart disease. E. Sodium, Potassium and chlorine: These constitute 2, 5 & 3% respectively of the total mineral content of the body. Sodium and potassium are extracellular elements while potassium is mainly an intracellular element. Sodium and potassium are primarily responsible for the potential differences existing across the membranes of nerve and muscle cells, which facilitate the conduction of nerve impulses. Adequate daily intake of NaCl should not be more than 6gm a day. The sodium and chloride ions are also important in digestive fluids as sodium bicarbonates in bile and pancreatic juice, and as hydrochloric acid in gastric juice. Potassium is a nearly constant component of lean body tissue, therefore when there is growth and development of lean tissue an adequate supply of potassium is essential. Deﬁciency: Potassium deficiency results in muscular weakness or paralysis. A potassium deficiency from inadequate intake is unlikely since potassium is widely distributed in foods. Sodium and chloride deficiency leads to loss of energy and confusion. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 41 2. Micronutrients: trace minerals These are required in amounts of less than 20mg per day. Their absence leads to occurrence of deficiency diseases. These elements function as components of enzymes and of important organic compounds, such as haemoglobin and thyroxine. A. Iron: About 3-5 gm of iron is present in a healthy adult, of this about 70 per cent is in a functional form as a constituent of haemoglobin, myoglobin, and a number of enzymes which catalyse oxidation and reduction process in the cell. The remaining 30% is storage iron, it is stored in the liver, bone marrow and spleen as ferritin and haemosiderin. Iron is a component of haemoglobin, plays an important part in the transport of oxygen from lungs to the tissue and of CO2 from cells to the lungs. Iron is present in the pigments and the enzymes in the tissue serves to bring about the transfer of oxygen within the cells. Iron also plays a role in the conversion of ꞵ carotene to vitamin A, synthesis of purines, clearance of blood lipids, and the detoxification of drugs in the liver. Iron deficiency results first in the reduction of stored iron and after it is depleted, a reduction in haemoglobin concentration and size occurs (microcytic hypochromic anaemia). Anaemia is caused due to diets deficient in iron, protein and the vitamins folate. B12, B6 and Vit C, or due to poor absorption over long periods. Loss of blood through illness, injury, or haemorrhage and excessive loss of blood during menstruation. AbsorpUon: Ferrous (Fe2+) salts are more easily absorbed than the ferric (Fe3+) salts. Ascorbic acid, presence of calcium, and physiological state such as growth and pregnancy, enhance iron absorption. The iron absorbed is stored in the body as ferritin and haemosiderin. The stored iron can be mobilized for haemoglobin synthesis. When the red blood cells disintegrate, the non protein portion of haemoglobin is split into an iron containing substance (haematin) and then to a pigment (bilirubin). Almost all the iron and much of the pigments are saved to be used over again in the synthesis of new red corpuscles. Organ meat such as liver, kidney, and heart are rich in iron. Lean meats, eggs, pulses, nuts, dried fruits, whole grains and green leafy vegetables are good sources. Milk and milk products are practically devoid of iron. B. Fluorine: FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 42 Fluorine (fluoride) is present in small, widely varying concentration in practically all soils, water supplies, plants and animals. It is therefore constituent of normal diets. Because of its ubiquity, a severe fluoride deficiency is rare. Fluoride is incorporated into bone and tooth enamel. It protect against dental carries, on an intake of 1.5mg per day or more. A higher intake (water containing 2 or more mg per litre of fluoride) produces mottling of the teeth in children. Chronic fluoride toxicity, fluorosis, is seen only in persons consuming more than 20mg per day over an extended period. 1.5-4mg is safe and adequate in adults. C. Zinc: It is constituent of enzymes involved in most major metabolic pathways. Zinc containing enzymes are involved in Nucleic acid synthesis and degradation. Large amounts of zinc are stored in bones. Deﬁciency: Signs of deﬁciency of Zinc in human are loss of appe8te, failure to growth, skin changes, impaired regeneration of wounds, low immunity, infertility and decreased taste activity. 15mg per day intake of zinc is recommended for adults. Phytic acid and fibre affect zinc availability adversely. Animal meats and sea foods are much better sources of available zinc than vegetable products. D. Copper: It is present in combination with plasma protein, ceruloplasmin, which is the transportable form of copper. Deﬁciency: Deficiency of copper results in anaemia due to the improper mobilization of iron from iron storage sites. In animals, copper deficiency leads to a variety of abnormalities including anaemia, skeletal defects, defects in pigmentation and structure of hair, reproductive failure and cardiovascular diseases. Copper is also constituent of some enzymes. A daily copper intake of 2-3mg is recommended for adults and this is met by the normal daily diet. Food sources are oysters, nuts, liver, kidney, dried pulses. E. Iodine: Iodine is integral part of thyroid hormones, thyroxin, which have important metabolic roles. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 43 Deﬁciency: Enlargement of the thyroid gland (goitre). Sea foods are excellent source of iodine, in the absence of food containing iodine (in the form of iodate and iodide of potassium), use of iodized salt can rectify iodine deficiency. F. Chromium: In the absence of chromium, there is disturbed glucose metabolism in human. Chromium levels in human tissue declines with age. Brewer’s yeast, meat products, cheese, whole grains and spices are good source of Chromium. G. Cobalt: Strangely cobalt deficiency has never been described for human. The major role of cobalt in the body is to serve as a part of vitamin B12. Inorganic cobalt is necessary for the microbial synthesis of vitamin B12 in the gut of animals. Human being have ability to obtain vit B12 from cobalt due to synthesis by microorganisms. This explains why true vegetarians can live for many years without Vit B12 in the diet. Other micro-minerals: Silicon, vanadium, tin, selenium, nickel and molybdenum. The amount of these nutrients required for human beings is not yet been estimated. Water Water next to oxygen is the most important constituent of life. It functions in digestive absorption, circulation and excretion. Water helps maintain the electrolyte balance of the body and plays a role in maintenance of body temperature. Water is not only a solvent but it also participate in several reactions, either as a reactant or as a product. Fruit and vegetable contains more than 90% water, milk is 87% water and meat 60 to 75% water, even dried fruits such as figs and raisins contain 20% water. Water is also dispersion medium in foods. Too much water in food can be danger as it favours the growth of undesirable bacteria and other microorganisms, the aim of modern food technology is to keep the water content of many foods as low as possible to increase shelf life. Physical properUes of water: Properties Consequences Excellent solvent Transport of nutrient and waste products High dielectric constant Solubility of ionic and polar compounds (universal solvent) High surface tension Physiological control factor: droplet and surface Highest density in liquid state at 40 C Floating ice High heat of vaporization Controls the transfer of vapor between atmosphere and water High heat capacity Stabilization of temperature FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 44 Chemistry of Water: The chemical formula for water is H2O. Water contains strong covalent bonds that hold the two hydrogen atoms and one oxygen atom together. The oxygen can be regarded to be at the center of a tetrahedron, with a bond angle of 104.5o between the two hydrogen atoms in liquid water and a larger angle of 109o between the hydrogens in ice. The bonds between oxygen and each hydrogen atom are polar covalent bond. As a result, each hydrogen atom is slightly positively charged and each oxygen atom is slightly negatively charged. Therefore they are able to form hydrogen bonds. A hydrogen bond is a weak bond between polar compounds where a hydrogen atom of one molecule is attracted to an electronegative atom of another molecule. It is a weak bond relative to other types of chemical bonds such as covalent or ionic bonds. Water would be expected to be gas at room temperature if compared with similar compounds in terms of their positions in the periodic table, but because of the many hydrogen bonds it contains, it is liquid. Due to its V-shape, each molecule of water can form up to four hydrogen bonds with its nearest neighbors. Each hydrogen atom can form one hydrogen bond, but the oxygen atom can form two, which results in a three-dimensional lattice in ice. The structure of ice is dynamic and hydrogen bonds are continually breaking and reforming between different water molecules. Because liquid water has a smaller bond angle than ice, the molecules can be packed together more tightly, and so the coordination number, or in other words the average number of nearest neighbors is higher for water than for ice. Types of water: Free water and Bound water Most natural foods contain water up to 70% of their weight or greater unless they are dehydrated, and fruits and vegetables contain water up to 95% or greater. Water that can be extracted easily from foods by squeezing or cutng or pressing is known as free water, whereas water that cannot be extracted easily is termed as bound water. Bound water usually is deﬁned in terms of the ways it is measured; diﬀerent methods of measurement give diﬀerent values for bound water in a par8cular food. Many FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 45 food cons8tuents can bind or hold onto water molecules, such that they cannot be removed easily and they do not behave like liquid water. Some characteris8cs of bound water include: It is not free to act as a solvent for salts and sugars: Bound water has more structural bonding than liquid or free water; thus, it is unable to act as a solvent It can be frozen only at very low temperatures (below freezing point of water). It exhibits essentially no vapor pressure: As the vapor pressure is negligible, the molecules cannot escape as vapor Density of bound water is greater than that of free water: the molecules in bound water are more closely packed than in the liquid state, so the density is greater An example of bound water is the water present in cac8 or pine tree needles—the water cannot be squeezed for pressed out; extreme desert heat or a winter freeze does not nega8vely aﬀect bound water and the vegeta8on remains alive. Even upon dehydra8on, food contains bound water. Entrapped water: Water molecules bind to polar groups or ionic sites on molecules such as starches, pec8n, and proteins. Water also may be entrapped in foods such as pec8n gels, fruits, vegetables, and so on. Entrapped water is immobilized in capillaries or cells, but if released during cutng or damage, it ﬂows freely. Entrapped water has proper8es of free water and no proper8es of bound water. Almost all food processing techniques involve the use of water or modiﬁca8on of water in some form: freezing, drying, emulsiﬁca8on (trapping water in droplets), bread making, thickening of starch, and making pec8n gels are a few examples. Further, because bacteria cannot grow without water, the water content has a signiﬁcant eﬀect on maintaining quality of the food. This explains why freezing, dehydra8on, or concentra8on of foods increases shelf life and inhibits bacterial growth. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 46 CHAPTER- 06 PIGMENTS AND COLOURS Pigments and Colours The colour of food can serve as a useful criterion on quality. It can be indicator of many types of deteriorative changes undergone by the food. Change of colour during preparation of food is a useful index of the required degree of cooking. Colour also provides a useful guide to quality control and is used by the food processor as a criterion for selecting raw materials. The characteristic colour of raw food is due to natural pigments present in the plant and animal materials. Therefore, to achieve the desirable colour and acceptability, an understanding of pigments and colour is necessary. A. Chlorophylls: These are green pigments involved in photosynthesis in plants and some microorganisms. There are a number of chlorophylls such as chlorophyll a, b, c and d; bacteriochlorophylls a and chlorobium chlorophylls. In foods only chlorophylls a and b, found in higher plants are important, these are fat soluble in nature. They are present in the leaves in the chloroplasts, normally in ratio 3:1, embedded between a layer of protein and lipid with carotenoid alongside. The chlorophylls have characteristic absorption and fluorescence spectra, which are useful in the analysis of the pigments. Chlorophylls are complex molecules containing four pyrrole rings with magnesium in the centre. The conjugated tetrapyrroles are known as porphyrins. Chlorophyll b has same structure as chlorophyll a except that in position three there is a formyl group instead of methyl group. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 47 In the presence of an acid the central magnesium of the chlorophyll is replaced by hydrogen giving pheophytins, with a dramatic change in colour from green to dull olive brown. The phytol group present in chrorophyll is removed by enzyme chlorophyllase resulting in the formation of chlorophillides which are green compounds. If the magnesium in the chlorophillides is removed, then the corresponding pheophorbides are formed,which have same colour as pheophytins. In the presence of an acid the central magnesium of the chlorophyll is replaced by hydrogen giving pheophytins, with a dramatic change in colour from green to dull olive brown. The phytol group present in chrorophyll is removed by enzyme chlorophyllase resulting in the formation of chlorophillides which are green compounds. If the magnesium in the chlorophillides is removed, then the corresponding pheophorbides are formed,which have same colour as pheophytins. The above reaction are responsible for the deterioration of the chlorophyll pigment in the processing and storage of foods. Green vegetables subjected to heat processing and subsequent storage turn from bright green to a dull olive brown colour due to the conversion of chlorophyll to pheophytin. Chlorophyll containing vegetables also show colour changes upon freezing and subsequent storage, the colour change in this case is influenced by the time and temperature of blanching before freezing. The formation of pheophytin from chlorophyll is related to the amount of acids produced within the system during heating and storage. For example, frozen raw peas lose more colour than beans because of the greater acidity of the peas. A number of attempts have been made to preserve the green colour of heat processed green vegetables. Chlorophillides are more stable than chlorophylls, therefore chlorophylls are converted to chlorophillides by means of the naturally occurring chlorophyllase, however, this enzyme functions at a temperature in the range of 65-750 C. Because of high temperature used, products processed by this method lose colour on standing. Another method is the use of alkalizing agents to produce a higher pH in the system and thus minimize pheophytin formation. HTST method has also been used to stabilize the molecule during heat processing. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 48 B. Myoglobin and Haemoglobin: The colour of fresh muscles is due to myoglobin. Muscle pigments also include cytochromes, some haemoglobin, vitamin B12; these pigments contribute little or nothing to total colour of muscle. Haemoglobin is the red pigment of blood, both myoglobin and haemoglobin serve to complex with the oxygen required for the metabolic activity of the animal. Myoglobin and haemoglobin are complex proteins, consisting of the protein moiety globin and non protein part haem. Haem like the chlorophylls is a porphyrin made up of four pyrrole units and contains an atom of iron in the reduced state (Fe+2) in the centre of the molecule. Myoglobin contains one globin moiety attached to a haem group, haemoglobin contains four globins attached to four haem groups. The iron atom in haem has a open position for complexing with water or other compounds, it is this complexing that is responsible for different colours of meat. It unites reversibly with oxygen, converting myoglobin which is pink red in colour to oxymyoglobin which is bright red. On prolonged exposure to oxygen, the reduced form of iron to myoglobin gets oxidized (Fe2+), resulting in formation of metmyoglobin which is brown in colour. The formation of brown metmyoglobin is accelerated by high temperature, oxygen pressure, fluorescent light, salts and presence of metals. In fresh meat, the production of indigenous reducing substances constantly reduces metmyoglobin to myoglobin. Myoglobin also combines with nitric oxide, then nitric oxide myoglobin is formed, which is stable red pink pigment. When meat is cured with nitrite, the latter is converted to nitric oxide and nitrosomyoglobin is formed. When the nitrite cured meat is heated there is a thermal denaturation of globin and more intense pink colour, is formed. The iron in this complex is still in ferrous state. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 49 C. Anthocyanins: These pigments are responsible for the red, purple and blue colour of fruits, vegetables and flowers. These are water soluble compounds occurring in the cell sap, and these belongs to the class of flavonoids. Anthocyanins contain sugar moiety along with it, which is responsible for its high solubility in water. The reactions they undergo results in decolouration and this is pH and temperature dependent. At low pH, the colour of anthocyanin is intense red, as the pH rises the colour changes from red to purple. These colour changes are due to changes in the molecular structure of anthocyanins. In the presence of sulphite or sulphur dioxide, there is a rapid bleaching of anthocyanins. Removal of sulphite by boiling and acidification results in the regeneration of the anthocyanins. Ascorbic acid reacts with anthocyanins, resulting in the degradation of both the compounds. The effect of ascorbic acid is of particular importance in the preparation of fruit juices. An intermediate peroxide is formed by the degradation of ascorbic acid and this may be responsible for the reaction with anthocyanins. Oxidation of ascorbic acids is catalysed by copper and iron compounds and this results in a greater oxidation of the anthocyanins. Many enzymes present in plants bring about the degradation of anthocyanins. These include glycosidase, phenolases and peroxidases. Leukoanthocyanins are colourless compounds which, during processing and handling are converted into coloured products. When heated in an acid solution, leukoanthocyanins are converted into anthocyanidins. Some canned fruits develop colour with time, this is due to the acid present in fruits converting leukoanthocyanins to anthocyanidins. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 50 D. Flavonoids: These are also polyphenolic substances with structure similar to those of anthocyanins. These include the groups of compounds, flavones, flavonols, flavanones. The yellow flavonoid pigments are widely distributed and it is difficult to find a plant in which flavonoids are not present. They may be sole pigments in such vegetables as potato and yellow skinned onion. The major group of flavonoids found is nature is the flavonol group consisting of quercetin, myricetin. The flavonoid compounds are usually more stable to heat. The three flavonol quercetin, kaempferol, and myricetin are found in considerable amounts in tea. E. Tannins: Tannins are complex mixtures of polymeric polyphenols. The catechins and related compounds belongs to this group. The appearance of tannins ranges from colourless to yellow or brown Tannins contribute to the astringency of foods and also to enzymic browning reactions. Sources: coffee, tea and nuts F. Betalains: These are group of pigments found in beet root, and to some extent in cactus fruits, and some flowers like bougainvillea. The pigments are red and yellow and resembles the anthocyanins and flavonoids in Appearance The betalains are stable in the pH range 4-6 and they are subject to degradation by thermal processing as in canning. G. Quinones and xanthones: A large group of pigments found in the cell sap of flowering plants, fungi bacteria and algae, are derivatives of anthraquinone, napthoquinone, and benzoquinone. A number of synthetic dyes are also derivatives of quinones. The natural quinone range in colour from pale yellow to almost black. Anthraquinone derivatives are the largest group of natural quinone pigments, followed by those of napthoquinone and benzoquinone. Xanthones are a group of yellow pigments. One well known member is mangiferin, which occurs as a glucoside in mangoes. H. Carotenoids: Carotenoids, also called carotenes, are a group of lipid soluble hydrocarbons and their oxygenated derivatives are called xanthophylls. They derive their name from the principal colouring matter of carrot roots, namely carotene. They are found in most yellow and red fruits and many roots. The colour of egg yolk and some fish is due to carotenoids. Widely occurring carotenoids are ꞵ carotene and zeaxanthin. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 51 Other pigments like lycopene in tomatoes, capsanthin in red pepper and bixin in annatto, predominate in certain plants. Carotenoids exists in nature as the free state in plant tissues or in solution in lipid media.ꞵ carotene is the precursor of vitamin A, it yields two molecule of Vitamin A by a cleavage at the centre of the molecule. The stability of carotenoids varies widely in foods. As the compounds are unsaturated they are susceptible to oxidation with concurrent loss of colour. Oxidation takes place both in presence of enzymes and nonenzymatically the pigments may auto oxidise by reaction with atmospheric oxygen at rates dependency on light, heats and presence of pro-oxidants. In the presence of unsaturated fatty acids lipoxygenase bring about the oxidative degradation of carotenes. Carotenes also change colour by undergoing isomerization from trans to cis configuration. The orange red colour of trans compounds changes to lemon yellow in cis form. Carotenes obtained from natural extracts from annatto, saffron, paprika, tomatoes, etc, are used as food colourants. Extracts from carrot, butter fat, and palm oil, which are yellow in colour have ꞵ carotene and thus show vitamin A activity. These natural extracts have been supplemented in many cases with synthetic carotenoids. FSSAI CFSO & TO FOOD CHEMISTRY E-Book Swa Education 52 CHAPTER- 07 FLAVOURS Flavours Flavor is composed of taste and odor. Other quali8es like texture or temperature contribute to overall sensa8on of ﬂavor. The main tastes are Salty (sodium chloride), Sweetness (sugar), Sourness (all acids like citric, tartaric etc), Bimerness (quinine), Umami (glutamic acid). The important odors are Camphoraceous (camphor), Pungent (formic acid), Etheral (chloroform), Floral (terpineol), Pepperminty (menthone), Musky (Androsan-ol), Putrid (skatole). Flavor Compounds Vola8le compounds in food like alipha8c esters, aldehydes or ketones are responsible for aroma of foods. The important groups of ﬂavoring compounds are as follows: Flavonoids They are responsible for flavor of fruits like orange, lemon. The peel of these fruits contain flavanone glycosides like Hesperidin (tasteless) and naringenin (bitter). Terpenoids They are omnipresent in plant foods. They contribute to flavor of citrus fruits and are major components of citrus oils. The major constituent of the essential oils i

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