Food Chemistry Notes PDF

10/11/2024 1  Course contents to be covered during semester Water: Properties, water activity, Lipids: Classification, structure, fatty acids, properties, emulsifiers, rancidity. Proteins: Classification, structure, amino acids, physical, chemical and functional properti...

10/11/2024 1  Course contents to be covered during semester Water: Properties, water activity, Lipids: Classification, structure, fatty acids, properties, emulsifiers, rancidity. Proteins: Classification, structure, amino acids, physical, chemical and functional properties, spoilage. Carbohydrates: Classification, structure, nomenclature, properties - physical, chemical, caramelization, Maillard reaction. Minerals: Major mineral elements, trace elements. Colours: Natural colors, artificial colours, pigments – properties, functions, stability. Flavours: Characteristics - taste, odor, astringency, off-flavor. Vitamins: Classification, properties and stability. 10/11/2024 2  Food Any substance that when ingested, usually will supply to the body one of the following: o Materials from which body can produce movement, heat or other forms of energy o Materials for the growth, repair or regeneration and reproduction o Substances necessary to regulate the processes of growth and repair 10/11/2024 3  Food chemistry It is the study of the chemistry of foods, their deterioration, and the principles underlying the improvement of foods for the consuming public It is the application of chemistry to the development, processing, packaging, preservation, storage, and distribution of foods and beverages for the purposes of obtaining a safe, economical, and aesthetically pleasing supply of food for people worldwide 10/11/2024 4  Constituents of foods Foods generally are made up of biochemicals, mainly derived from living sources such as plants and animals The general compositions of a food as well as the way in which the components are organized give a food its individual characteristics For example whole milk and fresh apples have about the same water content, but one is solid and the other is fluid because of the way the components are arranged 10/11/2024 5  All foods contain one or more of the following major constituents: 1. Water 2. Carbohydrates 3. Lipids 4. Proteins 5. Vitamins 6. Inorganic materials 7. Other substances (pigments flavors organic acids toxicants anti-nutritional factors etc.) 10/11/2024 6  Water, carbohydrates, lipids and proteins are found in large quantities and the other three i.e. vitamins inorganic materials and other constituents Water Ever present and one of the most important constituents It is the largest constituent of the human body More than 60% of an adult man is water, while woman contain 45-55% water 10/11/2024 7  Most of the water (55%) is held inside the cell as intracellular fluid, while the rest (about 45%) is contained in the extra-cellular fluid About 7.5% water is in blood stream that forms part of the extra-cellular fluids 10/11/2024 8  Chemical nature of water Water's chemical description is H2O One atom of oxygen bound to two atoms of hydrogen 10/11/2024 9  The hydrogen atoms are "attached" to one side of the oxygen atom, resulting in a water molecule having a positive charge on the side where the hydrogen atoms are and a negative charge on the other side, where the oxygen atom is Since opposite electrical charges attract, water molecules tend to attract each other, making water kind of "sticky" 10/11/2024 10  The side with the hydrogen atoms (positive charge) attracts the oxygen side (negative charge) of a different water molecule All these water molecules attracting each other mean they tend to clump together This is why water drops are, in fact, drops Water is called the "universal solvent" because it dissolves more substances than any other liquid Wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients 10/11/2024 11  The water molecule dissociates to yield H+ and OH- ions H2O H+ + OH- Hence it is a proton donor as well as proton acceptor and is neutral When an acid is added to water, it increases the proton donors (H+) and makes the water acidic 10/11/2024 12  The addition of an alkali increases the proton acceptors (OH-) ad makes the water alkaline Pure water has a neutral pH of 7, which is neither acidic nor basic As foods contain numerous compounds in their water content therefore have a pH below 7.0 10/11/2024 13  Physical properties Water is unique in that it is the only natural substance that is found in all three states -- liquid, solid (ice), and gas (steam) -- at the temperatures normally found on Earth Water freezes at 32oF and boils at 212oF (at sea level, but 186.4°F at 14,000 feet) In fact, water's freezing and boiling points are the baseline with which temperature is measured 10/11/2024 14  0oC on the Celsius scale is water's freezing point, and 100o is water's boiling point. Water is unusual in that the solid form, ice, is less dense than the liquid form, which is why ice floats Water has a high specific heat index i.e. it can absorb a lot of heat before it begins to get hot The high specific heat index of water also helps regulate the rate at which air changes temperature, which is why the temperature change between seasons is gradual rather than sudden, especially near the oceans 10/11/2024 15  Water has a very high surface tension or it is sticky and elastic, and tends to clump together in drops rather than spread out in a thin film. Surface tension is responsible for capillary action, which allows water (and its dissolved substances) to move through the tiny blood vessels in our bodies Density: 1 gram per cubic centimeter (cc) at 39.2°F, 0.95865 gram per cc at 212°F 10/11/2024 16  Functions of water Water is required in the bodies to perform the following functions Used as a building material in every cell, fatty tissues contain 20%, bone 26% and striated muscles 75% water Acts as lubricant in the joints and between the internal organs Regulates the body temperature 10/11/2024 17  Serves as medium in which the nutrients, enzymes and other chemical compounds are dispersed and dissolved It is a medium in which intracellular chemical reactions take place It participates in chemical reactions, especially in the hydrolytic ones Acts as transport medium for carrying nutrients to cells and removing waste from body 10/11/2024 18  Nature of water in foods Water exists in water in foods as free and as chemically and physically bound The free water as found in tomato and orange juice is available for chemical and biochemical reactions as well as for use by the microorganisms This water can be frozen or removed from the food system 10/11/2024 19  In physically bound water, the forces involved are of a physical nature, as is the case when water is strongly adsorbed to the surfaces of macromolecules such as proteins, starches and celluloses Chemically bound water involves the chemical linkages o water molecules to various food constituents such as carbohydrates and salts as water of hydration Such water is difficult to remove during drying and may not separate during freezing 10/11/2024 20  The bound water provides reduced chemical and biochemical reactions as well as microbial activity depending upon its degree The stability of foods increases with lowering of water 10/11/2024 21  Nature of food dispersions Water molecules have a dipole nature and dissolve salts in ionic but polar compounds dissolve because of hydrogen bonding between water molecules and groups such as alcohols, aldehydes and ketones Several components are found dispersed in water phase in the foods A dispersion is a system in which particles are dispersed in a continuous phase of a different composition like carbohydrates, lipids, proteins, vitamins etc. 10/11/2024 22  Food solutions are dispersions in which solid or semi-solid particles are evenly distributed in water Colloidal solutions are made up of long chain macromolecules consisting of aggregated molecules of proteins, lipids etc. Important example is ketchup Food gel is a type of dispersion that consists of a continuous phase of interconnected particles intermingled with a continuous water phase 10/11/2024 23  Food Solution: Description: A solution where a solute (like sugar) is completely dissolved in a solvent (like water), resulting in a homogeneous mixture at the molecular level. Characteristics: Clear or translucent; stable as long as the solute remains dissolved. Colloidal Solution: Description: A type of mixture where particles (like proteins or starches) are dispersed throughout another substance (like water) but do not dissolve completely. These particles are larger than molecules but still very small. Characteristics: Can be translucent to opaque; particles are dispersed at the microscopic level, resulting in a homogeneous appearance. ketchup  Food Gel: Description: A semi-solid system created by the gelling agent (like gelatin or pectin) forming a network that traps a liquid, creating a gel-like structure. Characteristics: Semi-solid with a network structure; the gel can be transparent or opaque and holds the liquid within its matrix. Emulsion: Description: A mixture where tiny droplets of one liquid (like oil) are dispersed in another liquid (like water). Emulsions require stabilizers to prevent separation. Characteristics: Milky or opaque appearance; the stability can vary, and separation can occur over time without proper emulsifiers.  Emulsion is another type of dispersion in which two immiscible liquids are dispersed In emulsion there are two phases; dispersed phase (droplets of one liquid) and continuous phase (the the other liquid) Important examples are butter, milk, margarine etc. 10/11/2024 26 10/11/2024 27  Role of water in foods Water contributes greatly to the desirable native qualities of foods Presence of water in the required amount and form is necessary for acceptable quality pf food The amount and state in which it appears are important in determining the storage life of a food Fresh fruits and vegetables are high in moisture with sufficient available moisture 10/11/2024 28  Such foods have shorter shelf life than grains and dry seeds that contain much less water, mostly bound in the cells Recognition of water amount and its availability for physical, chemical and biological changes in food systems helps to understand about the spoilage of foods and their prevention 10/11/2024 29  Water activity Defination Water Activity (aw):Water activity is a measure of the availability of water in a food product. It is defined as the ratio of the vapor pressure of water in the food to the vapor pressure of pure water at the same temperature. Water activity ranges from 0 (completely dry) to 1.0 (pure water). Water is an essential elements for all forms of life Serves as a medium for most metabolic activities Act as a carrier of nutrients and waste products to and from the body of an organism Like higher plants and animals microorganisms require moisture for their activities 10/11/2024 30  Moulds are capable of growing in very low available moisture Yeast and bacteria require more moisture for their activities Each organism has a minimal, maximal and an optimal water activity (Aw) for growth Amount of moisture available for microbial and other activities, as it affects the foods, can be considered in terms of equilibrium relative humidity and water activity 10/11/2024 31  This can be defined as equal to one hundredth part of the corresponding relative humidity in moisture equilibrium with the food i.e. Pure water has AAww=1 =whereas ERH most of the fresh 100 foods have Aw=0.99 Available water and water activity decreases exponentially with the addition of sugars and salts in a particular food 10/11/2024 32  Dry foods like wheat and rice are regarded as safe because of their low moisture contents available for microbial growth During humid conditions, some mould growth may be evident due to condensation of moisture, as it provides free moisture necessary for proliferation of these organisms The foods with higher moisture contents than in the stable foods support the growth and activities of most microorganisms leading to spoilage 10/11/2024 33  Role of Aw in food processing Most of the microorganism require an optimum amount of water for their growth Lesser is the moisture, lesser is the microbial growth and greater is the shelf life Manipulation of water contents is the principle rule in food processing to control microbial activities This basic principle is kept in mind during the processes of dehydration, evaporation and concentration when sugars salts and other water binding substances are used in foods 10/11/2024 34  Foods Aw Microorganism Distilled water, fresh meat, fish, milk, fruits, vegetables 1.0 Cl. Botulinum Sauces Most bacteria 0.9 S. aureus (anaerobic) Flours, cakes, cereals Most yeast S. aureus (aerobic) Salt preserved foods, jams 0.8 0.7 Xerophilic fungi Dried fruits 0.6 Extremely osmophilic Dehydrated foods microorganism 0.5 10/11/2024 35  aw and growth of microorganisms 10/11/2024 36  Controlling aw in foods Equilibration with atmosphere of known relative humidity Water removal (e.g., dehydration) 1. Addition of solutes (humectants) 2. Sugars 3. NaCl 4. polyhydric alcohols (glycerol, sorbitol), propylene glycol Control loss or gain of moisture in packaged foods 10/11/2024 37  Predicting Food Spoilage The aw of a solution may dramatically affect the ability of heat to kill a bacterium at a given temperature A population of Salmonella typhimurium is reduced tenfold in 0.18 minutes at 60°C if the aw of the suspending medium is 0.995 If the aw is lowered to 0.94, 4.3 min are required at 60°C to cause the same tenfold reduction 10/11/2024 38  The regulations (21 CFR 113.3(e) (1) (ii)) state that commercial sterility can be achieved by the control of water activity and the application of heat The risk of food poisoning must be considered in low acid foods (pH > 4.5) with a water activity greater than 0.85 10/11/2024 39 Type of chemical reactions due to water 1. Hydrolysis Reactions Description: Hydrolysis involves the breakdown of chemical bonds in compounds through reaction with water. This process is crucial for the transformation of various food components. Examples: Starch Hydrolysis: In the presence of water, starches can be broken down into simpler sugars (e.g., during cooking or in the digestion process). Fat Hydrolysis (Lipid Hydrolysis): Fats and oils break down into fatty acids and glycerol, which can lead to rancidity if the process continues unchecked. Significance: Texture and Consistency: Affects the texture of foods, such as making sauces thicker or breaking down starchy foods. Flavor Changes: Lipid hydrolysis can produce off-flavors and odors due to rancidity.  2. Enzymatic Reactions Description: Many enzymatic reactions in food are dependent on moisture. Water acts as a medium for enzyme activity, influencing the rate and extent of these reactions. Examples: Enzymatic Browning: In fruits and vegetables, the enzyme polyphenol oxidase (PPO) catalyzes the oxidation of phenolic compounds in the presence of moisture, leading to browning (e.g., apples turning brown when cut). Protein Hydrolysis: Enzymes such as proteases break down proteins into peptides and amino acids in aqueous environments, influencing the texture and flavor of foods (e.g., tenderizing meat). Significance: Color and Texture Changes: Affects the appearance and texture of food products. Nutrient Changes: Can lead to the loss or alteration of nutrients.  3. Gel Formation Description: Certain polysaccharides and proteins can form gels when hydrated. The gelation process often requires the presence of water to create a network structure. Examples: Gelatin: When mixed with water and heated, gelatin forms a gel upon cooling, used in desserts like jellies and marshmallows. Carrageenans: These seaweed-derived polysaccharides form gels or thickened solutions when hydrated, depending on the type of carrageenan used. Significance: Texture and Structure: Provides desirable textures in a wide range of food products, from desserts to meat substitutes  4. Solubility and Dissolution Description: Water is a universal solvent and affects the solubility of various compounds, including sugars, salts, and proteins. Examples: Sugar Dissolution: Sugars dissolve in water, which is essential for creating syrups and sweetening beverages. Salt Solubility: Salts dissolve in water, influencing the flavor and preservation of foods (e.g., brining). Significance: Flavor and Preservation: Enhances flavor by dissolving seasonings and helps in the preservation of foods through salting and brining.  5. Hydration of Ingredients Description: Hydration refers to the process where water molecules interact with and are absorbed by food ingredients, affecting their physical properties. Examples: Flour Hydration: In baking, water hydrates flour proteins (glutenin and gliadin), which form gluten and contribute to dough elasticity and texture. Legume Soaking: Dry legumes absorb water, swelling and softening, which is necessary for cooking and improving digestibility. Significance: Texture and Functionality: Affects the texture and functional properties of ingredients, influencing the final product quality  6. Microbial Growth and Fermentation Description: Water is essential for the growth of microorganisms involved in fermentation processes, which can be influenced by moisture levels. Examples: Bread Fermentation: Yeast requires moisture to grow and ferment sugars, producing carbon dioxide and causing dough to rise. Cheese Ripening: Moisture affects the activity of bacteria and molds in cheese, influencing flavor and texture development. Significance: Flavor and Shelf-Life: Microbial activity impacts the flavor, texture, and shelf-life of fermented foods.  LIPIDS Of the 4 macromolecule groups, the most loosely classified Nomenclature sometimes confusing and overlapping Difficult to give definitions – too many different types – usually water-insoluble organic compounds found in biological systems Highly reduced (i.e. oxidation-reduction) carbon- rich substances & insoluble in water 10/11/2024 46  It is a large and diverse group of naturally occurring organic compounds that are related by their solubility in non-polar organic solvents (e.g. ether, chloroform, acetone & benzene) and general insolubility in water Either hydrophobic (non-polar) or amphipathic (polar and non-polar regions) Types of lipids for domestic & industrial purposes include oils, margarine & butter, dripping, shortening, tallow, waxes 10/11/2024 47  General characteristics 1. Oily & greasy feel (leaves greasy spot on filter paper) 2. Not easily mix with water (float on water) 3. Dispersed in detergent, hot water or alcohol 10/11/2024 48  Properties of lipids that are important in foods Energy source – high caloric density 9 kcal/g Melting point- MP determines whether a lipid is oil or fat at room temperature Can be heated to high temp (150-230oC) – a good cooking medium –allows browning of foods during frying Can become rancid – 2 types of rancidity 10/11/2024 49  Lipolytic rancidity: Gives rise to free fatty acids – more prone to oxidation, aroma of short chain fatty acids Have ability to form emulsions with water and air 10/11/2024 50  The lipids of physiological importance for humans have four major functions 1. They serve as structural components of biological membranes 2. Provide energy reserves, predominantly in the form of triacylglycerols 3. Both lipids and lipid derivatives serve as vitamins and hormones 4. Lipophilic bile acids aid in lipid solubilization 10/11/2024 51 Fats and Oils contd.. Chemically, esters of fatty acids with glycerol and mixtures of: - i. Mono-glycerides – one molecule of fatty acids + 1 molecule of glycerol. ii. Di-glycerides – two molecules of fatty acids + 1 molecule of glycerol. iii. Tri-glycerides – three molecules of fatty acids + 1 molecule of glycerol. Most fats and oils are triglycerides. 52 Functions- fats and oils Several roles - nutritional, functional, sensory a. Provide energy – 9 kcal or 37.7 KJ/g b. Provide essential fatty acids - linoleic acid c. Carry fat-soluble vitamins d. Dissolve flavours, colours - make food attractive e. Make food more palatable f. Lubricate food making easier to swallow g. Provide feeling of satiety h. Provide fatty acids, cholesterol - form cell membranes in all body organs I. Help formation of retina, central nervous. 53  Fats and oils – functions contd Stored fat in body: a. Serve as energy reserve b. Protect organs - heart, kidney and viscera from shock and injury c. Help maintain constant body temperature by providing insulating layer under skin d. Contribute to body shape 54  Classification A. Based on origin a. Animal Mammal depot fat (lard, tallow), milk fat (ruminant), marine (fish oil) Marine – eicosapentanoic (EPA), docosahexaenoic (DHA) – in tuna, sardines – mostly unsaturated – biomedical advantages for human body b. Vegetable Seed oils (canola), fruit coats (olive oil), kernel oils (coconut oil) 10/11/2024 55  B. Visible / invisible 1. Visible Butter, margarine, shortening, cooking oils 2. Invisible fat in eggs, meat, poultry, fruits, vegetables , grain C. Based on melting point 1. Fats Solid / semisolid at room temp Usually of animal origin – margarine 2. Oils Liquid (low melting point) below room temp Usually plant origin - sunflower oil) 10/11/2024 56  D. Based on saponification Saponification is the process that produces soaps from the reaction of lipids and a strong base Two major classes based on their reactivity with strong bases. 1. Nonsaponifiable This class includes the "fat-soluble" vitamins (A, E) and cholesterol 2. Saponifiable The saponifiable lipids contain long chain carboxylic acids, or fatty acids, esterified to a “backbone” molecule, which is either glycerol or sphingosine 10/11/2024 57  The major saponifiable lipids are: 1.Triacylglycerides 2.Glycerophospholipids 3.Sphingolipids The first two use glycerol as the backbone Triacylglycerides have three fatty acids esterified to three OH groups on glycerol Glycerophospholipids have two fatty acids esterified at carbons 1 and 2, and a phospho-X group esterifed at C3 Spingosine, the backbone for spingolipids, has a long alkyl group connected at C1 and a free amine at C2, as a backbone 10/11/2024 58  Classification of common phospholipids, glycolipids, and triacylglyerides 10/11/2024 59  F. Based on structure Related structures are usually classed together Some groups of lipids with related structures are: 1. Simple Lipids 2. Compound Lipids 3. Terpenoids and Steroids 4. Derived lipids 10/11/2024 60  (I) Simple Lipids Triglycerides/neutral fats Found in adipose tissue, butterfat, suet, fish oils, olive oil, corn oil, etc Esters of three molecules of fatty acids plus one molecule of glycerol; the fatty acid may all be different Waxes Present in beeswax, head oil of sperm whale, carnauba oil, and lanolin Composed of esters of fatty acids with alcohol other than glycerol; of industrial and medicinal importance. 10/11/2024 61  (II) Compound Lipids Phospholipids (phosphatides) Found chiefly in animal tissues Bound in ester linkage to a nitrogenous base Lecithin Found in brain, egg yolk, and organ meats Important in fat metabolism and transport Used as emulsifying agent in the food industry 10/11/2024 62  Cephalin Occurs predominantly in nervous tissue Plays a role in blood clotting Plasmalogen Found in brain, heart, and muscle Lipositol Found in brain, heart, kidneys, and plant tissues together with phytic acid Important in cell transport processes 10/11/2024 63  Sphingomyelin Found in nervous tissue, brain, and red blood cells Source of phosphoric acid in body tissue Glycolipids 1. Cerebroside Makes myline sheaths of nerves, brain, and other tissues Yields on hydrolysis of fatty acids, sphingosine, galactose (or glucose), but not fatty acids Includes kerasin and phrenosin 10/11/2024 64  2. Ganglioside Present in brain, nerve tissue, and other selected tissues, notably spleen 3. Sulfolipid: Sulfur-containing glycolipid; sulfate present in ester linkage to galactose White matter of brain, liver, and testicle; also plant chloroplast 4. Proteolipids: Complexes of protein and lipids having solubility properties of lipids A part of brain and nerve tissue 10/11/2024 65  (III) Terpenoids and Steroids 1. Terpenes Large group of compounds made up of repeating isoprene units; Vitamin A of nutritional interest; fat soluble Vitamin E and K, which are also related chemically to terpenes. Found in essential oils, resin acids, rubber, plant pigments such as caotenese and lycopenes, Vitamin A, and camphor Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH₂=C−CH=CH₂. 10/11/2024 66  2. Sterols a. Cholesterol A hard, waxy substance that melts at 149°C (300°F) and is made from excess calories that the body does not require Found only in the animal foods like in egg yolk, dairy products etc. The body makes steroid hormones from cholesterol: corticosteroids, and the sex hormones, estrogen, progesterone, and testosterone Bile acids, vital to digestion, are derived from cholesterol It protects the skin, where it is converted to Vitamin D by the sun, and acts as a barrier against substances trying to enter or leave 10/11/2024 68  Acts as an antioxidant when the need arises Cholesterol in the brain and spinal cord accounts for about 25% of the body's total Cholesterol prevents certain liquids from penetrating the body and keeps water from leaving the body too quickly, therefore reducing evaporation losses of water Though body can make it (producing about 800 mg. per day), it cannot break it down It can only be removed from the body through feces in the form of bile acids, the removal is increased with the addition of fiber and water to the diet 10/11/2024 69  b. Ergosterol Found in plant tissues, yeast, and fungi Converted to Vitamin D2 on irradiation c. 7-dehydrocholesterol Found in animal tissues and underneath skin Converted to D3 on irradiation d. Androgens and estrogens Sex hormones, found in ovaries and testes e. Adrenal corticolsteroids Adrenal cortex, blood 10/11/2024 70 (IV) Derived lipids Important groups include fatty acids, alcohols and hydrocarbons Derived lipids are lipid molecules that are derived from simple lipids (like triglycerides and phospholipids) through hydrolysis or other modifications. They typically include compounds that have specific biological functions. Examples of derived lipids include: Fatty Acids: Saturated and unsaturated fatty acids, such as palmitic acid and oleic acid. Glycerol: A backbone for triglycerides and phospholipids.  Properties of Lipids The structure of these molecules determines their function e.g. insoluble triacylglycerides are used as the predominant storage form of chemical energy in the body In contrast to polysaccharides such as glycogen (a polymer of glucose), carbon atoms in the acyl- chains of the triacylglyceride are in a highly reduced state 10/11/2024 73 Fatty Acids Fatty acid - chain of carbon atoms, each with hydrogen atoms attached Chain ends in acidic group (COOH), able to combine with glycerol Dozens of fatty acids in nature Differ in number of carbon atoms and double bonds, they contain Classified on: Chain length Chemical structure Nutritional requirements 74  Classification on Chain Length a. Short chain fatty acids Fatty acids that contain 8 or less than 8 carbon atoms in their structure Examples: Acetic (C-2), butyric (C-4), caproic (C-6) and caprylic acids (C-8) Have low melting point More easily digested than long chain fatty acids. 75  Classification on Chain Length b. Long chain fatty acids Contain 10 or more carbon atoms in their chain Examples: Capric (C-10), lauric (C-12), myristic (C-14), palmitic (C-16), palmitoleic (C-16), stearic (C-18), oleic (C-18), linoleic (C-18), linolenic (C-18), arachidic (C- 20), and arachidonic (C-20) acids Melting point rises as chain length increases. 76 Classification on chemical structure Saturated Fatty Acids General formula CnH2nO2 or CnH2n+1.COOH. Contain maximum number of hydrogen atoms their chemical structure will permit Have no double bonds in their structure Quite stable Higher melting point Animal fats, hydrogenated fats contain more saturated fatty acids than plant and fish oils. 77 Classificatrion on chemical structure Saturated fatty acids - contd Saturated fatty acids like lauric, myristic and palmitic raise blood serum cholesterol level Occur most commonly Palmitic acid widely distributed, may contribute 10– 50% of total fatty acids in any food Makes up to 35% of all fatty acids in animal fats and up to 17% in plant oils and fish Palm, palm kernel and coconut oils contain more saturated fatty acids than other plant oils Intake saturated fatty acids should not provide more than 10% energy Examples of saturated fatty acids – next slide. 78 Saturated fatty acids contd - sources Fatty Acid Mol. formula C Sources Arachidic C20H40O2 20 ground-nut oil Stearic C18H36O2 18 most fats and oils Palmitic C16H32O2 16 palm oil Myristic C14H28O2 14 butter, coconut Lauric C12H24O2 12 coconut oil Capric C10H20O2 10 coconut oil Caprylic C8H16O2 8 coconut oil Caproic C6H12O2 6 butter Butyric C4H8O2 4 butter 79  Classificatrion on chemical structure Unsaturated Fatty Acids General formula: CnH2n-1COOH or CnH2n-3.COOH or CnH2n-5.COOH One or more double bonds in structure Susceptible to spoilage - react with air Lower melting point than saturated fatty acids Proportionately more unsaturated fatty acids in majority plant and fish oils than animal fats In nature, oleic acid (18 C atoms, one double bond) most common – most fats contain 30 to 65% of their total fatty acids as oleic. 80 Unsaturated fatty acids - contd Monounsaturated fatty acids have no effect on blood cholesterol Polyunsaturated fatty acids ( two or more double bonds) help reduce blood cholesterol level Less effective in reducing than saturated fatty acids in raising Linoleic acid (C 18, 2 double bonds) abundant in plant oils Cotton seed, groundnut, soybean, corn, sunflower and safflower oils contain 70 to 91% polyunsaturated fatty acids, only 9 to 26% saturated fatty acids Examples next slide. 81  Examples: Unsaturated fatty acids & sources Fatty Acids Mol. C dou- Source Caproleic C10H18O2 10 1 Butter fat Lauroleic C12H22O2 12 1 Butter fat Myristoleic C14H26O2 14 1 Butter fat Palmitoleic C16H30O2 16 1 Fish oils, beef Oleic C16H30O2 18 1 Most fats, oils Elaidic C18H34O2 18 1 Butter fat Vaccenic C18H34O2 18 1 Butter fat Linoleic C18H32O2 18 2 Most veg oils Linolenic C16H30O2 18 3 Soybean, canola Cadoleic C20H38O2 20 1 Some fish oils Arachidonic C20H32O2 20 4 Lard Erucic C22H42O2 22 1 canola, rapeseed 82 Nutritional Classification Essential Fatty Acids Cannot be synthesised in human body Linoleic acid, linolenic acid - essential Linoleic acid (18 C, 2 double bonds) found in corn and soya bean oils Linolenic acid (18 C, 3 double bonds) occurs in small amounts in vegetable oils, especially linseed (flaxseed, alsi) 83 Essential fatty acids - contd Precursors for group of hormone-like compounds - regulate variety of physiological functions Needed for formation of: cell membranes retina central nervous system Positive effect on growth and brain development. 84 Essential fatty acids contd Linoleic acid acts also as precursor of other essential fatty acids, considered essential for growth and maintenance of normal skin Deficiency in infants gives rise to eczema - dry thickened and scaly skin with oozing into body folds and changes in hair texture Deficiency very rare Essential fatty acids be present in diet to provide up to about 3% energy intake 85  Nutritional Classification Non-essential fatty acids Except linoleic, and linolenic acids, all others considered as non-essential Available in abundant quantities in foods of animal and plant origin If deficient, can be synthesised in body. 86  Fatty acids The “building blocks” of functional lipids The common fatty acids of plant tissues are C16 and C18 straight-chain compounds with zero to three double bonds of a cis configuration There are many different fatty acids and they can be assembled into their final form in molecules in a number of ways e.g., in phospholipids, a glycerol backbone is linked to two FA molecules and one phosphate 10/11/2024 87  Do not generally exist free in large quantity in vivo but are complexed to other molecules depending on their function Fatty acid chain is composed of an even number of carbon atoms Hydrophobic nature arises from lack of dipoles formed by C-H and C-C bonds present in chains: neither C nor H is very electronegative (versus which 2 elements found commonly in biomolecules 10/11/2024 88 10/11/2024 89  Functions of Essential Fatty Acids: EFA are the precursors for the production of prostaglandins which govern vitality, growth, mental state, and energy production Prostaglandins are a group of lipid compounds derived from fatty acids that perform a variety of physiological roles in the body. These are necessary for oxygen transfer and have the ability to hold that oxygen in cell membranes acting as a barrier to viruses, bacteria, fungi, and other foreign invaders EFA speed healing by reducing inflammation in some immune dysfunctions such as arthritis 10/11/2024 90  Inhibit tumor growth Assist in hemoglobin production - vital to life Hold proteins, as well as oxygen, within cell membranes helping to create electrical currents for neurological transmission. Faulty transmissions result in nervous disorders Facilitate the conversion of lactic acid to water to carbon dioxide thereby speeding up muscular fatigue recovery Maintain stability in cell division by protecting chromosomes 10/11/2024 91  Superunsaturated fats Often referred to as 'Omega 3' EFA which include: 1. Stearidonic acid [SDA](18:4w3) is found in black current seed oil. 2. Eicosapentaenoic acid [EPA](20:5w3) is manufactured by the body to make series 3 prostaglandins. 3. Docosahexaenoic acid [DHA](22:6w3), and EPA are found in cold water fish and marine animals 10/11/2024 93  Naming the fatty acid The number and placement of the double bonds affects the naming of the FA This also affects its chemical properties, and thus the properties of the lipid molecule into which it is incorporated, as well as the effect of the lipid on health Fatty acids have three naming protocols Consider a FA with 18 C and 1 C=C bond 10/11/2024 94  Least descriptive is the numbering notation 18:1 = 18 Cs, one double bond The traditional name is more descriptive but the position of any unsaturated bonds is not immediately obvious The systematic name tells the number of C in the FA chain, the degree of unsaturation, C=C bond placement in the molecule and its stereochemistry cis-Δ9-octadecenoic acid 10/11/2024 95  Systematic suffixes vary according to unsaturation 0 double bonds = octadecanoic acid 1 “ “ = -----------enoic acid 2 “ “ = -----------dienoic acid Systematic names also inform about position Numbering of C in FAs starts with carboxyl C C2 and C3 often called α and ß 10/11/2024 96  Methyl carbon at distal end of chain called ω- carbon atom Position of double bond(s) also indicated by Δ Cis-Δ9 indicates a double bond in cis between C9 and C10 Trans, trans- Δ9, Δ12 indicates 2 C=C bonds, both in trans between C9-10 and C12-13 10/11/2024 97  In practice, common names are used more often than systematic names When naming fatty acids, all carbons count: the carboxyl group as well as the alkyl chain Counting starts from the carboxyl carbon, and the numbering begins at the first carbon of the double bond In nature, almost all fatty acids have an even number of carbons This is due to the fact that fatty acids are synthesized stepwise from acetyl building blocks 10/11/2024 98  Basic Structure of Fatty Acids Fatty acids have a simple structure consisting of: A carboxyl group (-COOH) at one end (also known as the "alpha" end). A hydrocarbon chain (made of carbon and hydrogen atoms). A methyl group (-CH₃) at the other end (also known as the "omega" end). General formula: CH₃(CH₂)_nCOOH, where "n" refers to the number of carbon atoms in the chain. Examples: Butyric acid (C4:0) – 4 carbon atoms, no double bonds. Oleic acid (C18:1) – 18 carbon atoms, 1 double bond.  Systematic (IUPAC) Nomenclature In systematic (IUPAC) nomenclature, the fatty acid is named based on: The number of carbon atoms in the chain. The presence of any double bonds. The location of the double bonds relative to the carboxyl group. Steps for Naming: Count the total number of carbon atoms (including the carboxyl group). Identify the number and position of double bonds. Use the suffix “-oic acid” for saturated acids, and add “-enoic acid,” “- dienoic acid,” etc., for unsaturated acids..  Example: Palmitic acid (Hexadecanoic acid) Formula: C16:0 16 carbon atoms and no double bonds. IUPAC name: Hexadecanoic acid. Oleic acid (Octadec-9-enoic acid) Formula: C18:1 18 carbon atoms with 1 double bond at position 9 from the carboxyl end. IUPAC name: Octadec-9-enoic acid.  3. Common Nomenclature Fatty acids also have common names, often derived from the natural source where they were first found. Examples: Lauric acid (C12:0) – found in coconut oil. Linoleic acid (C18:2) – a polyunsaturated fatty acid found in plant oils  4. Omega (ω) Nomenclature The omega (ω) system is used to indicate the position of the first double bond relative to the methyl end (omega end) of the fatty acid. This system is important in nutrition, particularly for omega-3 and omega-6 fatty acids. Example: Alpha-linolenic acid (ALA, C18:3, ω-3) It has 18 carbon atoms and 3 double bonds. The first double bond occurs at the 3rd carbon from the omega (methyl) end. Linoleic acid (C18:2, ω-6) It has 18 carbon atoms and 2 double bonds. The first double bond is at the 6th carbon from the omega end.  5. Cis and Trans Isomers Double bonds in unsaturated fatty acids can exist in cis or trans configurations: Cis configuration: The hydrogen atoms attached to the carbons involved in the double bond are on the same side. This causes the molecule to bend. Trans configuration: The hydrogen atoms are on opposite sides, resulting in a straighter chain, similar to saturated fatty acids. Example: Oleic acid (Cis C18:1) – A natural fatty acid with a bent structure. Elaidic acid (Trans C18:1) – The trans version of oleic acid found in partially hydrogenated oils.  Physical Properties of Fatty Acids The physical properties of fatty acids are largely determined by the length and degree of unsaturation of the hydrocarbon chain Length The longer the fatty acid chain length, the poorer the solubility in water Because the carboxylic acid of the fatty acid is polar, it accounts for the moderate solubility of short-chain (less than 10 carbons) fatty acids in water 10/11/2024 107  The longer the fatty acid chain (assuming the degree of unsaturation remains the same), the higher the melting point Degree of Unsaturation Very important in determining the physical properties of fatty acids The fewer the double bonds in a fatty acid (assuming that the length of the fatty acid remains the same), the lower the solubility of the fatty acid in water 10/11/2024 108  The fewer the double bonds in a fatty acid, the higher the melting point of the fatty acid (assuming, the length of the fatty acid remains the same, and the double bonds present are all in the cis configuration The effect of the double bond on the physical properties of lipids is due to the conformation of the lipid that is caused by the double bond 10/11/2024 109  In saturated lipids (especially those of the same length), the most stable arrangement is very close packing of the side chains of the lipids, which is due to van der Waals interactions The packing is such that the lipids assume an almost crystalline array 10/11/2024 110  Because of the kink that results from cis double bonds, tight packing of fatty acid chains cannot take place Since the interactions between the these arrays are less extensive, it takes less energy to disrupt them, resulting in a lower melting point 10/11/2024 111  Double Bonds In nature, double bonds are most often found in the cis conformation There are cases where trans double bonds are known, however, these are seldom found in membranes A trans double bond fixes a given fatty acid in an extended conformation, similarly to how a cis double bond fixes a given fatty acid in a kinked (curved) conformation 10/11/2024 112  Key Points: Chain Length: Shorter chains (SCFAs) are more volatile, have lower melting points, and are generally liquid or volatile at room temperature. Longer chains (LCFAs and VLCFAs) have higher melting points, are solid at room temperature, and are more stable. Degree of Unsaturation: Saturated fatty acids (no double bonds) are more rigid, have higher melting points, and are solid at room temperature. Unsaturated fatty acids (1 or more double bonds) are less stable due to double bonds, have lower melting points, and are usually liquid at room temperature. The presence of cis-double bonds causes "kinks" in the structure, preventing tight packing and lowering the melting point.  Trans fatty acids can pack similarly to saturated fatty acids, and thus they have markedly higher melting points Trans fatty acids are often produced from healthy unsaturated fatty acids in a process called hydrogenation 10/11/2024 114  The goal of hydrogenation is to reduce the double bond by adding hydrogen gas across it This results in the raising of the melting point of oils like corn oil, safflower oil, or sunflower oil, so that they are solid around room temperature, this is how margarine is made Trans fatty acids have recently gained notoriety as being worse with respect to heart disease than even saturated fatty acids 10/11/2024 115  Trans fatty acids are found in a variety of cookies, chips, and commercial baked goods They can also be produced when oil is used for frying foods Double bonds can also be oxidized and cleaved to aldehydes and carboxylic acids when they sit in air for too long; this is what results in rancidity of oils 10/11/2024 116  Health hazards of trans fatty acids Essential fatty acids with a trans-configuration can no longer perform its critical function These imposters can interfere with the formation of long chain omegas, increasing the body's need for them and are basically misfits The cis molecules are "non-sticky," that is, able to disperse readily, while the trans molecules are "sticky," able to clump together making platelets more likely 10/11/2024 117  The body prefers to use trans fatty acids only as energy-creating fuels Trans molecules change cell membrane permiability impairing the protective barrier, increasing the likelihood of such foreign substances as allergens gaining entry The rate at which the body is able to break down the trans molecules is much slower than for the cis, important pertaining to the heart, whose normal fuel is fatty acids 10/11/2024 118  Due to changes in shape, trans molecules cannot take up sulfur-rich proteins, oxygen, and light vital to body reactions, thereby short- circuiting the messages to do so Trans fatty acids can increase blood cholesterol levels by as much as 15% and blood fat levels by 47% very quickly, leading to atherosclerosis Trans fatty acids disrupts the vital function of essential fatty acid designation of activity 10/11/2024 119  They worsen the activity by interfering with enzyme systems that can transform fatty acids into unsaturated fatty acid derivatives found in concentrated forms in the brain, sense organs etc. They also interfere with the production of prostaglandins that regulate muscle tone in the walls of the arteries, affecting blood pressure, kidney function, inflammation response, and immune system competences Neither the brain nor the placenta are completely protected from the permeation of trans fatty acids 10/11/2024 120  Emulsifiers Food is a complicated mixture of carbohydrate protein, oil and fat, water, and air, as well as a variety of other minute components such as minerals, vitamins, and flavors Food processing subjects this mixture to a wide range of thermal treatments, such as baking, boiling, steaming, freezing; and mechanical treatments, such as kneading, mixing, extruding etc, all of which further complicate the structure of the food The desired result of these treatments is good tasting food 10/11/2024 121  EMULSIFIERS  Emulsifiers are the molecules with one water-loving (hydrophilic) and one oil-loving (lipophilic) end that make possible for water and oil to become finely dispersed in each other, creating a stable, homogenous and smooth emulsion  On the basis of particle size, emulsions can be classified as 1. Micro emulsion Micro-emulsions are defined as the clear thermodynamically stable dispersions of two immiscible liquids, in which the dispersed particles consist of small droplets, whose size varies in the range of 100-1000 Å 2. Macro-emulsion Macro-emulsions are “mixtures of two immiscible liquids, one of them being dispersed in the form of fine droplets with diameter greater than 0.1 µm in another liquid Such system possesses a minimal stability, which may be accentuated by surface active agents and finely divided solids Food macro-emulsion systems are turbid, milky and thermodynamically unstable even after the addition of emulsifiers 123  There are two categories of emulsions with respect to phase system 1. An oil-in-water emulsion which contains small droplets of oil that are dispersed in water 2. Water-in-oil emulsion in which small droplets of water are dispersed in oil  Usually the water and oil will not mix and the emulsifier, or emulsifying agent, keeps the mixture stable and prevents the oil and water from separating into two phases 124  HISTORY  Egg yolk was probably the first emulsifier ever used in food production back in the early 19th century  Due to the short-term stability of egg yolk, the manufacturers switched to lecithin, derived from soybean that has been an important food product since the 1920  The most important breach for emulsifiers came after few years later when certain derivatives of acyl glycerol (mono- and di-glycerides) were introduced. Their use was patented for ice-cream production in 1936  Nowadays, food emulsifiers play an important role in the manufacture of food products such as margarine, mayonnaise, creamy sauces, candy, packaged processed foods, confections and a range of bakery products 125  FUNCTIONS OF EMULSIFIERS 1. To assist in the formation and stabilization of emulsions by decreasing the surface tension at the oil-water interface 2. To alter the functional properties of other food components and to modify the fat crystallization 3. To make a food appealing e.g. mayonnaise without the emulsifier shows how unappealing it would be if the oil and water separated before it was used 4. To modify the structure and texture of many food products 5. The processing of foods and also to help maintain quality and freshness 6. To prevent the growth of molds which can happen if oil and fat separated in low fat spread 126  MODE OF ACTION  Emulsifiers are molecules that have two distinct ends 1. One end likes to be in water (hydrophilic) 2. The other end likes to be in oil (lipophilic)  This means that an emulsifier will coat the surface of oil droplets in an oil-in-water emulsion and effectively 'insulate' the oil droplets from the water  It keeps them evenly dispersed throughout the emulsion and stops them from clumping together to form their own, separate layer. 127  In a water-in-oil emulsion, the emulsifier coats the water droplets to stop them separating from the oil  This property makes emulsifiers indispensable in the modern food industry where foams, suspensions (particles of solid dispersed evenly through a liquid) and emulsions are often used  Milk is a natural emulsion. It is a mixture of fat droplets in water  Proteins in the milk help to coat the fat droplets and allow them to stay dispersed in the water phase of the milk 128 FOOD EMULSIFIER CATEGORIES I. Lecithin and Lecithin Derivatives  Lecithin is a mixture containing phospholipids as the major component and widely found in plants and animals lipids  Soybean is the primary source of lecithin for use in the food industry  Soybean oil contains 1 to 3% phospholipids  Corn, sunflower, cotton seed, rape seed and egg are less significant sources 129  Lecithin is obtained by aqueous extraction from the soybean oil  Phase separation occurs on hydration of the phospholipids that is facilitated by centrifugation  The crude extract after water removal contains about 35% phospholipids and small amount of non- phospholipids materials  Extraction with acetone is used to produce an oil free lecithin  The term lecithin has been used to describe both phosphatidylcholine and mixtures of phospholipids  Triglycerides are soluble in acetone whereas phospholipids are insoluble 130  Classification of lecithin  Plant lecithin derived from soybean, corn, rapeseed, etc.  Fractionated lecithin isolated from special components of the raw materials  Yolk lecithin made by excluding the rest of phospholipids, which occupies about 30% of the egg yolk 131  Food applications of lecithin  Dairy products, e.g. imitation creams, desserts, edible ices  Confectionery, e.g. chocolate, chewing gum, toffees  Fats, e.g. margarines, spread, shortenings  Baked goods, e.g. bread, cakes, biscuits  Starch, e.g. mashed potatoes, pasta  Salad dressings and sauces  Instant drinks 132 2. Acetic Acid Esters of Monoglycerides  Acetic acid esters of monoglyceride called acetylated monoglycerides (AMG) are emulsifier in which acetic acid is bound with monoglyceride  It has little emulsifying activity Applications  Soft acetylated monoglyceride is able to expand by more than 8 times with tension  The combination of liquid acetylated monoglyceride and hydrogenated fats can improve the quality of fats e.g. margarine characterized with small temperature changes and wide plasticizing range can be produced 133  It is extremely stable oil whose peroxide value does not increase even when heated at 97.7 °C for long time  It is a liquid characterized by being less oily even at low temperatures and is available as a solvent, lubricant, plasticizer for vinyl acetate etc.  It is usable for foaming fats and oils by itself or in combination with other emulsifiers because of its stable alpha crystal structure  It is practically used as powdered foaming agents, solvents, plasticizers for gums and coating agents for food 134 3. Lactic Acid Esters of Monoglycerides (LMG)  In LMG lactic acid is bound with monoglyceride  It is used in shortening for cakes, desserts and foaming for cream by itself or in combination with monoglyceride 4. Citric Acid Esters of Monoglycerides (CMG)  In CMG citric acid is bound with monoglyceride and the products are mixtures containing a few monoglycerides  It is a highly hydrophilic emulsifier with a stable α- crystal structure used for margarine, dairy products such as, coffee whitener and cream  It is also used as an emulsion stabilizer for mayonnaise and dressing by utilizing its strong acid resistance 135 5. Succinic Acid Esters of Monoglycerides (SMG)  In CMG succinic acid is bound with monoglyceride  It is insoluble in cold water, dispersible in hot water and soluble in hot alcohol, fats and oils  Succinylated monoglyceride forms a complex with starch which is able to react with protein and is used as a dough modifying agent and as an emulsifier for shortening 6. Polyglycerol Polyricinoleate (PGPR) This is a strong lipophilic w/o emulsifier It is a highly-viscous liquid, insoluble in water and ethanol, and soluble in fats and oils It is used as a viscosity-reducing agent for chocolates 136 6. Diacetyl Tartaric Acid Esters of Monoglycerides (DATEM) In diacetyl tartaric acid ester of monoglyceride emulsifier, diacetyl tartaric acid is bound with monoglyceride It is dispersible in both cold and hot water, soluble in fats and oils It is a hydrophilic emulsifier and acid resistant, it is used for emulsification and foaming of margarine, mayonnaise and dressing It can also act on starch and protein and is used as a dough modifier 137 7. Polyglycerol Esters of Fatty Acids (PGE)  Polyglycerol esters of fatty acids are called polyglyceryl esters, in which fatty acids are bound by esterification with polyglycerine  It is dispersible in water and soluble in oil  Its hydrophilicity and lipophilicity greatly change with the degree of polymerization and with the nature of fatty acid  It has a variety of functions and is used for various purposes in many types of food as an o/w and w/o emulsifier such as in milk products containing acid, salt and a modifier to control the crystallization of fats 138  EMULSIFIER SELECTION Approval of the emulsifier by the appropriate government agency Desired functional properties End product application Processing parameters The synergistic effect of other ingredients Home preparation Cost 139 Types of Fat Deterioration Fat deterioration is a process by which fats degrade due to various factors like oxygen, light, heat, and microorganisms. The main types of fat deterioration include: Oxidative Rancidity (Lipid Oxidation) Hydrolytic Rancidity Microbial Degradation Thermal Decomposition Oxidative Rancidity (Lipid Oxidation) Oxidative rancidity is the most common and important form of fat deterioration. It occurs when fats react with oxygen, especially unsaturated fatty acids. This reaction leads to the formation of peroxides and further breakdown products such as aldehydes, ketones, and short-chain fatty acids, which cause off-flavors and odors. Stages of Oxidative Rancidity: Initiation: Free radicals are formed, often catalyzed by exposure to heat, light, or metals. Propagation: Free radicals react with unsaturated fatty acids, forming lipid peroxides. Termination: The reaction stops when free radicals are depleted or antioxidants neutralize them.  Initiation: The hydrogen atom is removed from the unsaturated fatty acid, producing a free radical: RH is the unsaturated fatty acid (lipid). R is the lipid radical. Propagation: The lipid radical reacts with molecular oxygen to form a peroxyl radical, which further reacts with another unsaturated lipid to propagate the reaction ROO is a peroxyl radical. ROOH is a lipid hydroperoxide (unstable and breaks down into smaller volatile compounds).  Termination: The reaction ends when two radicals combine to form a non-radical product: R +R →R-R  Factors Influencing Oxidative Rancidity: Degree of unsaturation: Polyunsaturated fats are more prone to oxidation than saturated fats. Presence of antioxidants: Compounds like vitamin E can inhibit oxidation. Exposure to light, oxygen, and metals: Light, air, and metal ions (iron, copper) can accelerate the oxidation process. Effects of Oxidative Rancidity: Off-flavors and odors (rancid, metallic taste) Decrease in nutritional value (loss of essential fatty acids, destruction of fat- soluble vitamins) Formation of toxic compounds (e.g., aldehydes, free radicals) Hydrolytic Rancidity Hydrolytic rancidity occurs when water molecules break down triglycerides into free fatty acids and glycerol. This reaction is often catalyzed by enzymes like lipases or exposure to moisture. The free fatty acids produced can have unpleasant odors and tastes. Factors Influencing Hydrolytic Rancidity: Presence of water: Moisture increases hydrolysis. Enzymes: Lipases from microbes or natural enzymes in food can accelerate the process. High temperatures: Heat can increase the rate of hydrolysis. Effects of Hydrolytic Rancidity: Unpleasant flavors: Free fatty acids, particularly short-chain ones (e.g., butyric acid), contribute to off-flavors. Reduced quality: Decrease in the sensory appeal and shelf life of the product. Impact on texture: Free fatty acids can affect the texture of food products, making them less desirable. Microbial Degradation Certain microorganisms, especially molds and bacteria, can degrade fats. Microbes produce lipase enzymes that break down triglycerides into glycerol and free fatty acids, causing off-flavors, odors, and spoilage. Factors Influencing Microbial Degradation: Storage conditions: Warm, humid environments promote microbial growth. Presence of moisture: Microbial activity increases in the presence of water. Hygiene practices: Poor hygiene can introduce microorganisms that degrade fats. Thermal Decomposition (Polymerization) When fats are exposed to high temperatures (e.g., during frying), they can undergo thermal decomposition. This involves the breaking of chemical bonds in the fatty acids, leading to the formation of toxic compounds like acrolein and polymerized triglycerides. Factors Influencing Thermal Decomposition: Type of fat: Saturated fats are more stable at high temperatures than unsaturated fats. Cooking temperature: Higher temperatures increase the rate of decomposition. Duration of heating: Prolonged heating accelerates thermal breakdown. Effects of Thermal Decomposition: Formation of harmful compounds like trans fats and polymerized fatty acids. Reduced nutritional value (destruction of essential fatty acids). Deterioration of flavor, color, and texture of food. Preventing Fat Deterioration To prevent or slow down fat deterioration, various methods can be employed: Use of antioxidants: Adding natural or synthetic antioxidants (e.g., vitamin E, BHA, BHT) can slow down lipid oxidation. Proper storage: Store fats and oils in cool, dark, and airtight conditions to reduce exposure to oxygen, light, and heat. Minimal processing: Avoid excessive heating or frying at high temperatures, which accelerates fat degradation. Reduction of moisture: Limiting water content can prevent hydrolytic rancidity and microbial growth. Hygiene and sanitation: Proper hygiene during food production and storage can minimize microbial contamination.  FAT DETERIORATIONS There are four types of undesirable changes which can occur in oils and fats that mainly lead to rancidity 1. Autoxidation It refers to objectionable off-flavor usually formed by the autoxidation of unsaturated fatty acids resulting in a mixture of volatile components mostly aldehydes and ketones 2. Hydrolytic In oils and fats the formation of free fatty acids and glycerol by de-esterification is often characterized by a “soapy” flavor The reaction is catalyzed by lipolytic enzymes i.e. lipases and is accelerated at low pH and high temperature conditions 150  Triglycerides containing fatty acids with short chain lengths (>12 carbon atoms) usually produce off-flavor upon hydrolysis such as in butter 3. Reversion Reversion is a type of odor and flavor degradation usually associated with fish and other highly unsaturated oils and fats. The flavor degradation is possibly brought about by oxidation of linolenic type acids 4. Polymerization Polymerization term is used to describe the cross- linking of oxidized unsaturated fats through two carbon atoms 151  Factors affecting rancidity Lipid oxidation moves through each of these three phases as a product ages and a number of factors can influence the rate of lipid oxidation in a product These include: 1. The initial quality of the fat or oil used for manufacturing the product, 2. Conditions used to manufacture the product, 3. Storage conditions (heat, light, packaging) 10/11/2024 152  4. Surface area exposed to atmospheric oxygen 5. Presence of transition metals Concentration of active lipoxygenases, 6. Application of appropriate of synthetic or natural preservatives 7. Presence of chemical oxidizers 10/11/2024 153 Phytochemicals in Food Chemistry: Reactions, Constituents, and Effects Dietary Intervention The branch of therapeutics that deals with the application of diet, dietary components and combinations in the prevention and treatments of the diseases Tools for Dietary intervention Functional Foods Nutraceuticals Designer foods Immune nutrition foods Anti-malgnient Foods  Goals Diet based therapies emerged as promising strategies addressing challenges;  Nutritional deficiencies  Better treatment tolerance  Protect immune function  Facilitate recovery and healing  Minimize nutrition-related side effects  Maintain strength and energy  $150 billion Global Nutrition Industry Vitamins & Minerals 14% Functional Food Herbs/ 37% Botanicals 13% Sports, Meal, Hom & Spec Natural/ Nutraceutic 8% Organic als Food 8% 20% 158 BENEFITS OF NUTRACEUTICALS OVER DRUGS Dietary Intervention DRUGS Energy/nutrition/necessary Treatment of disease for life Life long use and benefits Immediate effect All populations Target population Safe Benefit > risk Consumer selects Health provider prescribes 159 OXIDATION AND OXIDATIVE STRESS 160 Oxidation Aerobic metaboilsm reduces 95 to 98% inhaled oxygen into water Remaining fraction converted to reactive oxygen species (ROS) Singlet Oxygen Superoxide (O2- ) Hydroxyl (OH-) H2O2 ROS cause oxidative damage to Nucleic acid Carbohydrate Protein Lipids 161 Oxidative stress “A situation in which the amount of ROS exceeds the levels of antioxidants” Sources of oxidative stress Activation of phagocytic cells of immune system Production of nitric oxide by the vascular endothelium Release of iron and copper ions Vascular damage (Opara, 2004; Vina et al., 2006). 162 Oxidative stress (COnt…) Oxidative stress causes Process of aging Degenerative brain disorders Amyotrophic lateral sclerosis (ALS) Alzheimer's disease (AD) Parkinson's disease (PD) Gastrointestinal cancers Hypertension Diabetes and its complications (Kidd, 2005; Lau et al., 2005; Bjelakovic et al., 2004) 163 Antioxidants Antioxidants are compounds typically found in foods that significantly decrease the adverse effect of oxidative stress on body functions. Two principle mechanisms of action Chain-breaking mechanism Removal of ROS initiators 164 Types of Antioxidants Antioxidant Enzymes: Superoxide dismutase Catalase Glutathione peroxidase Antioxidant Vitamins: Tocopherol (vitamin E) Carotenes (vitamin A) Ascorbic acid (vitamin C) Other antioxidant free radical scavengers: Reduced glutathiones P- 450 enzymes 165 THEORY OF ANTIOXIDANTS Oxygen free radical Fatty acids, DNA, or cholesterol Antioxidant Antioxidants stops the chain reaction by changing the nature of the free radical. 166  Reactive Species Antioxidant O 2- Superoxide free radical. OH Hydroxyl free radical SOD, Vitamins, B-Carotene - RO Alkoxyl free radical ROO- Peroxyl free radical Vitamin E, Vitamin C H2O2 Hydrogen peroxide Catalase, Glutathione peroxidase LOOH Lipid peroxides Glutathione peroxidase 167  DNA repair Carcinogen metabolism Hormonal regulation Bioactive food components Cell cycle Differentiation Apoptosis 168  Phytochemical & free radical interaction in cancer progression Step Healthy cells attacked by Step Pre-cancer cell attacked by Step Cancer cell progresses into 1 free radicals 2 promoters 3 tumors Phytochemicals Slow down the process Phytochemicals preventive effect on from pre-cancer to overwhelmed cell degeneration cancer 169 Arteriosclerosis ROS--------Oxidation of Liver membranes---------oxidized cholesterol LDL+OXIC-------Blood vessel---------Damage the PUFA WBC+LDL-OC= Foam cells or plaque formation What are Phytochemicals? Definition: Phytochemicals are bioactive compounds produced by plants. While not classified as essential nutrients like carbohydrates or proteins, they play significant roles in maintaining food quality and imparting health benefits. Types of Phytochemicals: Flavonoids: Found in fruits, vegetables, and grains. Carotenoids: Color pigments in carrots, tomatoes, and peppers. Phenolic acids: Present in coffee, cereals, and berries. Alkaloids: Examples include caffeine (in coffee) and capsaicin (in chili peppers). Glucosinolates: Found in cruciferous vegetables like broccoli and Brussels sprouts. What are Phytochemicals? Definition: Phytochemicals are bioactive compounds produced by plants. While not classified as essential nutrients like carbohydrates or proteins, they play significant roles in maintaining food quality and imparting health benefits. Types of Phytochemicals: Flavonoids: Found in fruits, vegetables, and grains. Carotenoids: Color pigments in carrots, tomatoes, and peppers. Phenolic acids: Present in coffee, cereals, and berries. Alkaloids: Examples include caffeine (in coffee) and capsaicin (in chili peppers). Glucosinolates: Found in cruciferous vegetables like broccoli and Brussels sprouts.  Vitamins Minerals Vitamin A, C, E, K Zinc, Selenium Organosulphur compounds Carotenoids Allium, allyl sulphide, indoles ß-carotene, lycopene, Lutein, Zeaxanthin Antioxidants Antioxidant cofactors Low molecular Coenzyme Q10 weight antioxidants glutathione, uric acid Polyphenols Flavonoids Phenolic acids Flavonols -quercetin, kaempferol Hydroxy-cinnamic acids- ferulic, p-coumaric Isoflavonoids -genistein, daidzein Hydroxy-benzoic acids- Flavanols -catechin, EGCG gallic acid, ellagic acid Flavanones -hesperidin Anthocyanidins -cyanidin Flavones -chrysin 173 Phytochemicals as Food Constituents Phytochemicals serve critical roles in food systems, influencing various physical, chemical, and biological aspects. They contribute to the color, flavor, texture, and preservation of foods, making them valuable food constituents in the food industry. A. Color: Carotenoids and Anthocyanins: These pigments are responsible for the color of fruits and vegetables. For instance, carotenoids give an orange color to carrots, while anthocyanins provide red, purple, or blue hues in foods like berries and grapes. pH Sensitivity: The color of some phytochemicals, especially anthocyanins, is pH-dependent. For example, red cabbage turns reddish in acidic conditions and blue-green in alkaline conditions. Conti… B. Flavor: Volatile Phytochemicals: Compounds like terpenes and sulfur-containing phytochemicals affect the aroma and taste of foods. These contribute to the sensory profile of spices, herbs, and vegetables. Bitterness and Astringency: Tannins, found in grapes, tea, and some fruits, impart bitterness and astringency, influencing food's palatability. C. Texture: Tannins: The presence of tannins in foods like wine and fruits contributes to astringency, which alters the perception of food texture, making it feel dry or puckery in the mouth. D. Food Preservation: Natural Preservatives: Phytochemicals like phenolic acids, flavonoids, and tannins possess antioxidant properties that protect food from oxidation and spoilage. Their antimicrobial activities can also inhibit the growth of harmful microorganisms. Example: Rosemary extract, rich in polyphenols, is used as a natural preservative in processed foods. Conti… 3. Chemical Reactions Involving Phytochemicals in Food Systems A. Antioxidant Reactions: Oxidation-Reduction: Phytochemicals, particularly flavonoids and phenolic acids, act as antioxidants. They neutralize free radicals, thereby preventing oxidative degradation of lipids and proteins in food systems. Food Application: The use of antioxidants from natural sources like green tea extract in oils and fats helps extend shelf life by reducing rancidity. B. Maillard Reaction: Role of Phytochemicals: Phenolic compounds can modulate the Maillard reaction during cooking, affecting color and flavor development in roasted and baked foods. Food Example: Coffee beans contain phenolic compounds that participate in the Maillard reaction, influencing the dark color and rich aroma during roasting. 3.Chemical Reactions Involving Phytochemicals in Food Systems A. Antioxidant Reactions: Oxidation-Reduction: Phytochemicals, particularly flavonoids and phenolic acids, act as antioxidants. They neutralize free radicals, thereby preventing oxidative degradation of lipids and proteins in food systems. Food Application: The use of antioxidants from natural sources like green tea extract in oils and fats helps extend shelf life by reducing rancidity. B. Maillard Reaction: Role of Phytochemicals: Phenolic compounds can modulate the Maillard reaction during cooking, affecting color and flavor development in roasted and baked foods. Food Example: Coffee beans contain phenolic compounds that participate in the Maillard reaction, influencing the dark color and rich aroma during roasting. Conti… C. Enzymatic Browning: Polyphenols: Phenolic compounds, when exposed to oxygen in the presence of the enzyme polyphenol oxidase, can undergo oxidation leading to browning (as seen in cut apples and bananas). Prevention: To prevent browning, foods are often treated with ascorbic acid (Vitamin C), which inhibits the oxidation of phenolic compounds. Phytochemicals in Food Chemistry: Reactions and Effects A. Color, Flavor, and Stability: Pigmentation: Carotenoids, anthocyanins, and chlorophylls provide pigmentation to foods, but they are susceptible to environmental factors such as light, oxygen, and temperature. Understanding their stability is key to maintaining the appearance of processed foods. Flavor Compounds: Phytochemicals like terpenes and sulfur compounds (from garlic and onions) impact the sensory quality of foods by imparting characteristic aromas. B. Interaction with Nutrients: Nutrient Bioavailability: Some phytochemicals can enhance or inhibit the absorption of nutrients. For instance, flavonoids in tea can inhibit iron absorption, while carotenoids can increase the bioavailability of fat-soluble vitamins like Vitamin A. 5. Role of Phytochemicals in Health and Food Preservation A. Natural Antimicrobial Agents: Preservation Function: Phytochemicals like allicin (from garlic) and eugenol (from cloves) have antimicrobial properties that make them useful in preventing spoilage and extending the shelf life of food products. B. Antioxidant Properties: Health and Preservation: The antioxidant activity of phenolic compounds, flavonoids, and carotenoids helps protect cells from oxidative damage and also preserves food from lipid oxidation. Example: Green tea extract is rich in catechins, a type of flavonoid that exhibits strong antioxidant properties. Conti… C. Nutraceuticals and Functional Foods: Health Benefits: Phytochemicals are increasingly being used in the development of functional foods due to their potential health benefits, such as reducing inflammation, preventing cancer, and promoting heart health. Food Application: Fortifying foods with phytochemicals like resveratrol (in grapes) or lycopene (in tomatoes) can enhance their health-promoting properties while preserving food quality. Example of the role of phytochemicals Raw Tomatoes → Lycopene in natural trans-form. Processing → Peeling, chopping, breaking cell walls. Heat Treatment → Isomerization of trans-lycopene to cis-lycopene, enhancing bioavailability. Lycopene Release → Antioxidant effects, color stabilization. Finished Sauce → Bright red color, stable product with enhanced antioxidant properties. Impact of Processing on Phytochemical Activity in Food Chemistry Thermal degradation: Some phytochemicals like vitamin C, certain flavonoids, and anthocyanins are heat-sensitive, leading to losses during cooking, baking, or roasting. Enzyme inactivation: Heat and processing methods can deactivate enzymes like polyphenol oxidase, which prevents undesirable reactions such as browning in fruits. Transformation of compounds: In some cases, processing can convert phytochemicals into more bioactive forms (e.g., lycopene in tomatoes or beta-carotene in carrots).  | **Phytochemical Name** | **Processing Methods** | **Effect on Bioavailability in Food Products** | |------------------------|-----------------------------|---------------------------------------------------------------------------| | **Lycopene** | Cooking, boiling | Increased bioavailability through isomerization (trans- to cis-lycopene). | | **Anthocyanins** | Heat processing, HPP | Heat can degrade; HPP retains bioavailability and color. | | **Catechins** | Drying, brewing | Moderate heat increases bioavailability; excessive heat degrades. | | **Glucosinolates** | Steaming, boiling, fermentation | Steaming preserves; boiling reduces; fermentation increases bioavailability of breakdown products like sulforaphane. | | **Flavonoids** | Juicing, blending, thermal processing | Juicing increases release; thermal processing can degrade sensitive compounds. | | **Beta-carotene** | Cooking, pureeing | Increased bioavailability through cooking; enhanced in fat-containing matrices. | | **Isoflavones** | Fermentation (e.g., soy) | Increased bioavailability through microbial action. | | **Tocopherols (Vitamin E)** | Roasting, baking | Bioavailability increased with moderate heat; excessive heat degrades. | | **Phenolic Compounds** | Ultrasound, microwave processing | Enhanced extraction and bioavailability without significant degradation. | | **Vitamin C** | Boiling, freezing | Degraded by heat; freezing retains bioavailability in food products. |  Quiz Questions 1. How does reducing water activity (aw​) affect the shelf life of perishable foods? Explain using examples of dried fruits and cured meats 2. "Water is considered the universal solvent. Explain why water can dissolve ionic compounds like salt but not hydrophobic compounds like oil.“ 3. Explain how the water content in dough affects the final texture of bread. What role does gluten development play in this process 4. Differentiate between water activity (aw_ww​) and moisture content in foods. Can two foods with the same moisture content have different water activities?“ 5. "Describe how water contributes to gel formation in pectin-based jams and jellies. Why is the presence of sugar important in this process?" Dr. AlI imran 2018  Conti………………. 1. "Why does the freezing of water contribute to the degradation of food texture, particularly in fruits and vegetables?“ 2. "Explain the role of water in heat transfer during cooking. Why do foods cooked in water (e.g., boiling) often cook more evenly than those cooked in dry heat (e.g., baking)?“ 3. "Why can low-moisture foods like crackers and powdered milk still spoil despite having low water content? Discuss the relationship between water activity and microbial growth.“ 4. "How does water activity affect enzyme-catalyzed reactions in foods? Provide an example of a reaction that is influenced by water activity.“ 5. "Discuss the role of water in non-enzymatic browning (Maillard reaction) in baked goods. How does water content influence the extent of browning?" Dr. AlI imran 2018  Fats Question: "Compare and contrast the structures of saturated and unsaturated fatty acids. How does the presence of double bonds affect their physical state at room temperature?“ "Explain the chemical process by which trans fats are formed. Why are trans fats considered more harmful than cis fats for heart health?“ "Linoleic acid and alpha-linolenic acid are considered essential fatty acids. Why are these important for human health, and what foods are rich sources of these acids?“ "Describe the process of lipid oxidation and its effects on food quality. Which types of fatty acids are most susceptible to oxidation, and why?“ "Using the