Chapter 4: Chemistry of Food Composition - Lipids (دهون) PDF

CHAPTER 4: Chemistry of Food Composition – Lipids )‫(دهون‬ Lecturer: Norlelawati Arifin (FST) 20 March 2020 = 25 Rajab 1441 H  CHAPTER OBJECTIVES After completing this chapter, you will be able to: Describe between classes o...

CHAPTER 4: Chemistry of Food Composition – Lipids )‫(دهون‬ Lecturer: Norlelawati Arifin (FST) 20 March 2020 = 25 Rajab 1441 H  CHAPTER OBJECTIVES After completing this chapter, you will be able to: Describe between classes of lipid molecules and the chemical differences of fatty acids (C1) Compare chemical reactions of lipid terminology (C2) Identify the important functional properties of food lipids (C1) Identify the chemical structure and functional properties of food components such as carbohydrates, lipids, proteins, vitamins and minerals (C1 - LO1).  CHAPTER OUTLINE Lipid properties Lipid classification: simple, complex, precursor and derived lipids Fatty acids classification: length of carbon chain, level of saturation, shape Food lipids 1. Structure and types of lipids 2. Chemical reactions of lipids: fractionation, hydrolysis, interesterification, polymerization, hydrogenation, and oxidation 3. The functional properties of lipids in food systems: aeration, crystallization, emulsification, flavor, heat transfer, mouthfeel, plasticity, tenderization  INTRODUCTION Chemical term for what is commonly known as fats (‫)دهون‬ LIPIDS or oils (‫)زيوت‬ Provide a concentrated source of energy : 1 g = 9 kcal Triglycerides: Saturated plants and fats: meat, animals eggs, milk, lard, palm oil and coconut oil Source of lipids: Cholesterols: Plants and liver and egg Animals yolk, small amounts in Unsaturated In foods: whole milk, fats: seeds, contribute to the texture, butter, flavor and aroma nuts and plant cheese, and oils meats In digestive system: fats take longer to digest [Makanan Dan (Kami juga menumbuhkan untuk kamu) pokok (zaitun) yang asal tumbuhnya di kawasan Gunung Tursina, yang mengeluarkan minyak dan lauk bagi orang-orang yang makan. (Surah Al- Mu'minuun 23:20) [Gambaran makanan ahli neraka]: (Makanan ini pula panas) seperti minyak hitam yang mendidih dalam perut. (Surah Ad-Dhukhan 44: 45) [Gambaran hari Qiamat]: Selain itu (sungguh ngeri) ketika langit pecah- belah lalu menjadilah ia merah mawar, berkilat seperti minyak. (Surah Ar-Rahmaan 55:37)  Organic compounds – Contain C, H, O, sometimes N and P Insoluble in water BUT some fats, oils and waxes slightly soluble in water PROPERTIES LIPID Lipid properties  1) * Simple – made of fatty acid and CLASSIFICATION glycerol. e.g: triglyceride, waxes 2) * Complex (compound/ conjugated lipids) – made of fatty acid, glycerol and something else (P or N). e.g: LIPID phospholipids, glycolipids, sulpholipids 3) Precursor – hydrolysis products of simple and complex lipids. 4) Derived – made from metabolic processes. e.g: ketone bodies, steroids, prostaglandins * important in food lipids Lipid classification Lipid classification 1) Simple Lipids (Ester of fatty acids) 1) Triglyceride 2) Waxes (Fats and Oils) – Backbone NOT glycerol – Fatty acids with – Classified as true waxes, long chain cholesterol esters, vitamin A carboxylic esters and vitamin D esters acids – Performs external protective functions Lipid classification – simple lipids Simple Lipids Triglyceride Composed of 3 fatty acids (FAs) and a molecule of glycerol 3 FAs + 1 glycerol → Lipids Lipid classification – simple lipids  The 3 FAs in triglyceride Continue… ✓ Long chains of carbon atoms surrounded by hydrogen atoms ✓ Do not have the same FAs ✓ Differ in length of their carbon chain (2-22C) ✓ Differ in level of saturation - saturated, unsaturated or polyunsaturated ✓ Differ in shape Lipid classification – simple lipids  General Structure of a Fatty Acid Fatty acid Carboxylic acid with a long hydrocarbon tail Generally, R represents: Carboxyl group - the long hydrocarbon tail - a hydrocarbon chain of 3 to 22 carbon atoms Lipid classification – simple lipids Structure of Glycerol Glycerol A 3-carbon alcohol Polyol compound Backbone of a lipid Lipid classification – simple lipids  ESTER BOND Covalent bond Carboxyl group (-COOH) of fatty acids attached * to the hydroxyl group (-OH) of * glycerol molecule * Removal of 3 molecules of water * = Ester bond  Ester bond Example: TG FAs Lipid classification – simple lipids 2) Complex Lipids Also referred to compound or conjugated lipids They contain polar properties Generally have three or more chemical identities: fatty acids, alcohols, phosphates, nitrogenous bases and other compounds Examples: – Phospholipids - contain a phosphoric acid molecule and a fat molecule – Glycolipids - contain carbohydrate – Cerebrosides - contain a carbohydrate and a fat molecule – Sulpholipids - contain a sulfate radical Lipid classification – complex lipids Complex Lipids Phospholipid Phospholipid ✓ Composed of Glycerol 2 fatty acids Phosphate ✓ Soluble in water ✓ Sources: eggs, soybean Lipid classification – complex lipids  Continue… General Structure of a Phospholipid Lipid classification – complex lipids  3) Precursor Lipids Substance (inactive) that can be converted into other substance (active form) Different from TGs Examples: – Sterols – steroid alcohols – Cholesterols – Beta-sitosterols Lipid classification – precursor lipids Precursor Lipids Sterols Sterols ✓ Essential components of cell membranes and many hormones ✓ Soluble in water ✓ Sources: plants and animals Lipid classification – precursor lipids  Precursor Lipids Cholesterols Cholesterols ✓ Important precursor molecule for the biosynthesis of bile acids, steroid hormones and several fat soluble vitamins ✓ Insoluble in water ✓ Sources: found only in animal (organ meat such as liver and kidney) Lipid classification – precursor lipids  Continue… Structure of Sterol and Cholesterol Lipid classification – precursor lipids Precursor Lipids Beta-sitosterol Beta-sitosterol ✓ Reducing cholesterol ✓ Similar to cholesterol structure, EXCEPT they have an extra ethyl group on the side chain ✓ Insoluble in water ✓ Sources: found only in plants Lipid classification – precursor lipids 4) Derived Lipids Ketone bodies are ✓ derived from acetyl-CoA when carbohydrates are so scarce that energy must be obtained from breaking down fatty acids Prostoglandins are ✓ derived enzymatically from fatty acids and have important functions in the animal body Lipid classification – derived lipids  FATTY ACIDS CLASSIFICATION Length of carbon chain Level of saturation Shape Fatty acids classification  FATTY ACIDS CLASSIFICATION: Length of carbon chain Short chain Medium chain Long chain fatty acids fatty acids fatty acids (SCFAs) (MCFAs) (LCFAs) 2C to 6C 7C to 12C > 12C e.g: acetic e.g: caprylic e.g: oleic acid, acid, butyric acid, capric linoleic acid, acid, caproic acid, lauric linolenic acid, acid acid arachidonic acid Fatty acids classification – length of carbon chain FATTY ACIDS CLASSIFICATION: Level of saturation Determined by the number of double bonds between carbon atoms (C=C): 1) Saturated fatty acids: No double bond between carbon atoms 2) Monounsaturated acids (MUFAs): One double bond between carbon atoms 3) Polyunsaturated acids (PUFAs): Two or more double bonds between carbon atoms Fatty acids classification – level of saturation  Continue… Structure of Fatty Acid: Saturated No double bond Fatty acids classification – level of saturation  Continue… Structure of Fatty Acid: Monounsaturated One double bond Fatty acids classification – level of saturation  Continue… Structure of Fatty Acid: Polyunsaturated More than one double bond Fatty acids classification – level of saturation  Continue… Fatty acids classification – level of saturation Examples: Saturated and Unsaturated Fatty Acids Fatty acids classification – level of saturation  FATTY ACIDS CLASSIFICATION: Shape Determined by the saturation of the carbon chains Pack tightly together Solid at room temperature Saturated fatty acids – e.g: animal fats, butter and lard Do not stack together well Unsaturated fatty acids Liquid at room temperature – e.g: plant oils Fatty acids classification – shape Both H atoms are on the same side of the double bond The hydrogen atoms at the unsaturated region can be arranged in different positions H atoms are on opposite sides of the double bond Fatty acids classification – shape  continue… Fatty acids classification – shape  Trans form − small amount in nature − formed during food processing − raise blood levels of LDL cholesterol Fatty acids classification – shape  Continue… Cis form – different categories of PUFA – depend on the location of the first bond in the chain (methyl end) Fatty acid containing a Omega-3 (ω-3) C=C between the third fatty acids and forth carbons from the methyl end Omega-6 (ω-6) Fatty acid containing a fatty acids C=C between the sixth and seventh carbons from the methyl end Fatty acids classification – shape  Structure of Omega-3 Fatty Acid 3 4 Examples: Alpha-linolenic acid in vegetable oil, Eicosapentanoic acid (EPA), docosahexaenoic acid (DHA) in fish oils Fatty acids classification – shape  Structure of Omega-6 Fatty Acid 6 7 Examples: Linolenic acid in corn and safflower oils Fatty acids classification – shape Essential and Non-essential fatty acids Essential Fatty Acids Non-Essential Fatty Acids Need to be consumed Do not need to be by human for consumed by human maintaining health Cannot be made by Can be made by human human body body All EFA are Can be saturated or unsaturated fatty acids unsaturated fatty acids continue… Continue… Continue…  Olive oil Have a higher proportion of monounsaturated fats most notably oleic acid and linked with a reduction in the risk of coronary heart disease It also has a 10:1 ratio of fatty acids: 10% Omega-6 and 1% Omega-3 fatty acids An olive oil-rich diet results in higher concentrations of LDL cholesterol and a higher number of LDL subfraction particles than rapeseed oil and sunflower oil diets (Ref: Pedersen et al., 2000, Journal of Lipid Research, (41): 1901-1911) FOOD LIPIDS  1) Structure and characteristics of lipids Fats and Oils a) Saturated and Unsaturated Fat b) Cis and Trans Fat c) Melting Point  Fats and Oils Fats: Solid at room temperature Consisted of saturated fatty acids or by hydrogenation of double bonds (alkenes) Examples: butter, lard, tallow, margarine Oils: Liquid at room temperature Consisted of unsaturated fatty acid Examples: palm oil, coconut oil, soybean oil continue… a) Saturated and Unsaturated Fats FA FA Type Notation Melting Name point (oC) Elaidic Trans- C 18:1 43 unsaturated Oleic Cis- C 18:1 19 unsaturated Stearic Saturated C 18:0 70 Food lipids – structure and characteristics of lipids b) Cis and Trans Fat Food lipids – structure and characteristics of lipids  Continue… * * * Fats * * information (*) * * * * * Food lipids – structure and characteristics of lipids  c) Melting Point (MP) Fatty acids MP SCFAs < MP MCFAs < MP LCFAs chains Shapes MP cis < MP trans Mixture of TAG = range of MP Mixture of Physical = liquid, solid, plastic, triacylglycerols brittle, crystalline at room temperature Food lipids – structure and characteristics of lipids  Continue… Food lipids – structure and types of lipids  Types of Lipids Water soluble because of polar molecules Polar attached Examples: sterol molecule or steroid alcohol lipids Function in food as emulsifiers - e.g: phospholipid (lecithin) Natural pigments from lipids Pigments Examples: carotenoid, carotene (carrot), lycopene (tomato), anthocyanins, betalains, chlorophylls Esters of fatty acids and long carbon chain alcohols Waxes Examples: beeswax, candelilia, carnauba, parrafin 2) Chemical reactions of lipids a) Fractionation b) Hydrolysis c) Interesterification d) Polymerization e) Hydrogenation f) Oxidation  Stereospecific numbering System as recommended by a IUPAC-IUB commission on the nomenclature of glycerolipids IUPAC - INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY  One fatty acids are Monoacylglycerol attached to a backbone of (Monoglyceride) the three carbon molecule glycerol Two fatty acids are Diacylglycerol attached to a backbone of (Diglyceride) the three carbon molecule glycerol Three fatty acids are Triacylglycerol attached to a backbone of (Triglyceride) the three carbon molecule glycerol  Crude Oil Obtained from pressing or rendering Crude oil Compounds may destabilize flavor, stability, color Crude oil is refined to Refined oil improve oxidative stability RBD (Refining, Bleaching, Deodorization)  a) Fractionation FAs and TG in fats and oils are separated based on their chemical properties Produce Example: Higher melting point (HMP) Fractions with - e.g: stearic acid different melting + points Lower melting point (LMP) - e.g: oleic acid Chemical reactions of lipid – fractionation Example: Multi-step dry fractionation of palm oil (for commodity oils and specialty fats) Chemical reactions of lipid – fractionation  Continue… Not the same as Saturated fatty hydrogenation acids is removed fractionated oil? to make them More solid softer, and more liquid Application Frying oil Margarine Butter Palm olein (liquid fraction) - good resistance to Eliminate Improved spreadability oxidation trans fat out of the - longer shelf life of refrigerator finished products Chemical reactions of lipid – fractionation https://www.youtube.c om/watch?v=NkGspW AGDM8 Link to fractionation process of palm oil  b) Hydrolysis TG break down to free fatty acids and glycerol with presence of water, heat and enzyme (lipase) → LIPOLYSIS Produce Example: Production of butyric and DG, FFAs and caproic acid in butter glycerol It Creates CAUTION! hydrolytic rancidity Chemical reactions of lipid – hydrolysis  Continue… Water TG Glycerol 3 FFAs Chemical reactions of lipid – hydrolysis  Continue… Glycerol Lypolysis FFAs Undergo autoxidation hydrolytic LCFAs – no off-flavor rancidity SCFAs – smell and taste bad Effects Milk Milk, fruits Cheese chocolate and vegetables Small quantities of FFAs Small quantities of FFAs - contribute desirable flavor - contribute to off-flavor Chemical reactions of lipid – hydrolysis  c) Interesterification The removal of FAs from glycerol then rearrangement or recombination of FAs into many configurations Produce Example: Modified fats for nutritional and physical properties Chemical reactions of lipid – interesterification  Involves an interchange of fatty acid groups FA groups may exchange position within a TG or among TG molecules Enzymatic or non- enzymatic reaction S – Stearic O – Oleic L – Linoleic Chemical reactions of lipid – interesterification  Continue… Application This is generally done in order to modify the melting point and slow down rancidity process Oil Create oil more suitable for deep frying Create margarine in Margarine - good taste - low content of saturated FAs - high stability Shortening Create low-trans-fat products Chemical reactions of lipid – interesterification  d) Polymerization Hydrolized FAs link together to form large molecules of lipids or FAs polymers Produce Longer chain FAs Increase viscosity of oil Chemical reactions of lipid – polymerization  e) Hydrogenation Addition of hydrogen atoms to unsaturated fatty acids Produce Example: Convert oleic acid (liquid) More solid to stearic acid (solid) form of lipids Often creates CAUTION! trans fatty acids Chemical reactions of lipid – hydrogenation  Continue… Chemical reactions of lipid – hydrogenation  Continue… Example: Partially hydrogenation of linoleic oil create trans fats Chemical reactions of lipid – hydrogenation  Create Continue… Partially Fully trans fat Semi solid form hydrogenated Solid form Creamy, semi- oil? soft, butter-like Improves consistency oxidative Application stability Shortening, margarine, Peanut snacks, fried foods, Margarine butter pastries Prevent lipids from separating out in liquid (oil) Create trans fat form Chemical reactions of lipid – hydrogenation  Continue… Chemical reactions of lipid – hydrogenation https://www.youtube.c om/watch?v=6J26Wm vltzs Video on hydrogenation  f) Oxidation Oxygen react with double bond of unsaturated fatty acid → LIPOXIDATION Produce Examples: Off-flavor development - e.g: rancid smell and taste Major cause of oil Small organic compounds Food - e.g: aldehydes, ketones, deterioration FAs of lower molecular weight, hydroxyl acids Creates oxidative rancidity Chemical reactions of lipid – oxidation  Continue… Lipoxidation: Describe lipid oxidation mechanism in which heat, light, or metal trigger Autoxidation: Referred to as rate of oxidation increases as the reaction proceeds Lipoxidation involve three stages: 1) Initiation - formation of free radicals 2) Propagation - free-radical chain reaction 3) Termination - formation of non-radical products Prevent oxidative Antioxidant rancidity Chemical reactions of lipid – oxidation  Continue… Heat, light, metal Free radical Peroxide Hydroperoxide Affects characteristics such as flavor, color, texture and nutritive Chemical reactions of lipid – oxidation 3) The functional properties of lipids in food systems a) Aeration b) Crystallization c) Emulsification d) Flavor e) Heat transfer f) Mouthfeel g) Plasticity h) Tenderization  Edible Lipids Can be 1. Triglycerides divided into three 2. Phospholipids major Visible groups 3. Sterols Invisible  a) Aeration Process of incorporating air into a substance and makes product porous and light Fat crystal molecules hold air bubbles Produce expanded product, desirable volume and weight Important in bakery products = aerated batter creaming Examples: whipping foaming The functional properties of lipids in foods systems – aeration  b) Crystallization Process of intermolecular interactions to favor packing molecules close together Arrangement of the fatty acids on triglyceride molecules in solid phase Affect structure, texture, solubility, mouthfeel, aeration Important in chocolate making = crystalline structure [(α) , (ß), (ß’)] Examples: chocolate – beta - fat bloom lard – beta - fat crystal The functional properties of lipids in food system – crystallization  c) Emulsification Process of homogenous dispersion of oil and water Fat and water mix together in food system [O/W or W/O] Important in mayonnaise, salad dressing, ice-cream Emulsion = food emulsion Stabilized by cake Emulsifier / Examples: chocolate emulsifying agents ice-cream salad dressing The functional properties of lipids in foods systems – emulsification  d) Flavor and Aroma Fat as carrier of fat soluble flavors compounds and as solvent for carrying hydrophobic flavors and aromas Fat contribute flavor and aroma directly owing [vegetables oils] to their own intrinsic flavor or indirectly [absorb fat-soluble flavor from other food] Important to contribute flavor = contribute flavor - free fatty acids = remove flavor - reduced fat or fat free in processed foods Essential oils – terpenoids (spices, herbs) Examples: Fruit flavor – citrus fruit Meat flavor The functional properties of lipids in foods systems – flavor  e) Heat Transfer Oil provide most efficient modes of heat transfer during cooking Fat will enter to the food resulted in higher fat content, moisture migrate from food Important in = fried foods Example: frying foods in oils sautéing The functional properties of lipids in food systems – heat transfer  f) Mouthfeel Fat as lubricant in mouth Fat provide mouthfeel sensation - creaminess, smoothness in mouth Important in production of = fat substitutes / fat mimics - low calorie but retention of fat functional properties - provide satiety - resistant to digestion The functional properties of lipids in food systems– mouthfeel  Continue… Examples: Fat-based Substitutes - Caprenin - Salatrim- Short And Long chain Acid TRIglyceride Molecule - Olestra Protein-based Fat Substitute – Simplesse - from whey protein concentrate Carbohydrate-based Substitutes – Avicel – Carrageenan – Dextrins – Inulin The functional properties of lipids in food systems– mouthfeel  g) Plasticity Ability to hold its shape but still molded or shaped under light pressure Fats become pliable, flexible, and moldable by create homogenous structure BUT holds its shape Important = plasticity characteristics Examples: margarine, palm stearin, chocolate The functional properties of lipids in food systems– plasticity  h) Tenderization Fat can acts as a tenderizer Fat melts during cooking add moisture and flavor to the meat and serves as a natural tenderizer, moisture is trapped Important in = meat juiciness Cooked lean cut meat (low fat content) Examples: seems dry and tough to chew Marbled cut meat (high fat content) seems moist, tender and easier to chew The functional properties of lipids in food systems – tenderization  CONCLUSIONS Three major lipid functions in foods 1.Energy and health: fat contributes to making us feel satiated because 2.Flavor and aroma 3.Texture Solid vs liquid Emulsions Attributes and physicochemical properties of lipids are determined by types and positions of fatty acids on glycerol backbone Thank you ‫شكرا‬