Lecture 2. Food Chemistry – Lipids PDF

Lecture 4. Food Chemistry – Lipids FDSC 330. FUNDAMENTALS OF FOOD SCIENCE Dr. Oni Yuliarti Content Introduction to Lipids ▪ Terminology ▪ Function in Foods ▪ Source of Fat Fatty Acid ▪ What is fatty acid ▪ Classifications Other...

Lecture 4. Food Chemistry – Lipids FDSC 330. FUNDAMENTALS OF FOOD SCIENCE Dr. Oni Yuliarti Content Introduction to Lipids ▪ Terminology ▪ Function in Foods ▪ Source of Fat Fatty Acid ▪ What is fatty acid ▪ Classifications Other types of lipids ▪ Phospholipids ▪ Sterols ▪ Colouring Compounds ▪ Fat-Soluble Vitamins What are the main differences between fat and oil? 1. Terminology  Definition of lipids: ▪ Defined as a group of non-polar compounds ▪ Normally insoluble in water but soluble in non-polar organic solvents  E.g. Hexane, chloroform, iso-octane ▪ Includes: phospholipids, sterols and triacylglycerol classes  Lipids contain: ▪ Carbon (C) ▪ Hydrogen (H) ▪ Oxygen (O) Terminology  Fats are mixture of lipids ▪ Mainly triacylglycerols (92-98%) ▪ Small quantities of: sterols, mono- and diglycerides. ▪ Solid at room temperature  Oils are fats which is liquid at room temperature ▪ E.g.: soybean oil, canola, sunflower etc. Fat Oil (liquid)  2. Functions of Lipids in Foods 1. Nutritional Aspects  Source of energy: ▪ 30-40% of total calories ▪ Provides 9 cal/g  Carriers of essential nutrients ▪ Fat soluble vitamins (A, D, E, K) ▪ Essential fatty acids (ω3 & ω6 FAs)  Protective role from cancer & heart diseases Functions of Lipids in Foods cont.. 2. Organoleptic properties ▪ Pleasant mouth feel (creamy, smooth) ▪ Flavour carrier ▪ Texturizer (emulsions, margarine, butter) ▪ Off-flavors (oxidative and hydrolytic rancidity) Functions of Lipids in Foods cont.. 3. Cooking properties ▪ As a medium for cooking (frying oil) ▪ High boiling points than water  Fast cooking 4. Food additives ▪ Emulsifiers ▪ Carrier of antioxidants, pigments, flavour 3. Source of Fat and Oils  Animal and plants origin  The amount and types depend on the origin  Some examples: ▪ Meat and Fish ▪ Confectionary ▪ Processed Foods ▪ Butter, Margarine, Lard ▪ Egg yolk ▪ etc  Lipid Classification Simple lipids Complex Derived lipids (compound) lipids Mono-, di-, Phospholipids Fatty acids triglycerides Glycolipids Sterols Waxes Lipoproteins Fat-soluble vitamins Pigments- beta carotene ▪ Saponifiable (alkaline hydrolysis) Triglycerides, phospholipids, glycolipids ▪ Non-saponifiable Free fatty acids (FFAs), carotenoids, tocopherols ▪ Polar (amphiphilic) Phospholipids, glycolipids  Lipid Structure ▪ Formed mainly from glycerol and 3 fatty acids combined together by ester linkage.  GLYCERIDES H2 C OH HC OH O H2 C O C (CH 2 )16 CH3 Monoglyceride O H2 CO C (CH2 )16 CH3 ( C18 ) O HC O C (CH2 )14 CH3 (C16 ) O H2 C O C (CH2 )16 CH3 (C18 ) Diglyceride Triglyceride  Fatty Acids (FA) ▪ Long, unbranched chains of hydrocarbon atoms with methyl (CH3) and carboxyl group (COOH) Methyl end Acid end Non-polar, hydrophobic end polar, hydrophilic end fat soluble tail CH3 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - C - OH II O Omega end Alpha end Omega carbon Carprylic acid (8:0)  Fatty acid classification 1. Saturation 2. Number of double bonds 3. Position of double bonds 4. Configuration of double bonds 5. Occurrence of additional functional groups  Saturated Vs Unsaturated Fatty Acids Saturated FA: CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OH octanoic acid O Saturated FA: 8:0 caprylic acid CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OH Absence Unsaturated octanoic of Double bond! acidFA O caprylic acid 8:0 CH3 CH2 CH2 CH2 CH CH CH2 C OH 3-octenoic acid Unsaturated FA (8:1) O CH3 CH2 CH2 CH2 CH CH CH2 C OH 3-octenoic CH3 CH CH acid CH 2 CH CH CH O (8:1) C OH 2 3,6-octadienoic acid (8:2) O CH3 CH CH CH2 CH CH CH2 C OH 3,6-octadienoic acid (8:2) O Contain isolated double bonds  Isomers Cis Vs Trans (Unsaturated FA) H H CH2 C C CH2 ▪ The cis-trans terms are used Cis form to describe the positions of atoms or groups connected to doubly bonded atoms H ▪ Atoms/groups are cis or trans if they lie on same (cis) or CH2 C C CH2 opposite (trans) sides of a reference plane in the H molecule Trans form Characteristics of Fatty Acids ▪ Most of the natural fatty acids contain an even number of carbon atoms from 4 to 24 or more. ▪ All fatty acids differ in carbon chain length, degree of unsaturation, and position of double bonds → All of these determine melting properties of fatty acids.  SATURATED FATTY ACIDS Short Common Systematic MP MW Formula name name name (oC) 4:0 Butyric Butanoic acid 88.11 -4.5 CH3(CH2)2COOH 6:0 Caproic Hexanoic 116.16 -2.0 CH3(CH2)4COOH 8:0 Caprylic Octanoic 144.21 16.5 CH3(CH2)6COOH 10:0 Capric Decanoic 172.27 31.5 CH3(CH2)8COOH 12:0 Lauric Dodecanoic 200.32 44.0 CH3(CH2)10COOH 14:0 Myristic Tetradecanoic 228.38 58.0 CH3(CH2)12COOH 16:0 Palmitic Hexadecanoic 256.43 63.0 CH3(CH2)14COOH 18:0 Stearic Octadecanoic 284.48 71.0 CH3(CH2)16COOH 20:0 Arachidic Eicosanoic 312.54 77.0 CH3(CH2)18COOH  Unsaturated Fatty Acids Short Common Systematic MP MW Formula name name name (oC) 16:1 Palmitoleic Cis-9- ω7 hexadecenoic acid 254.4 1 CH3(CH2)5CH=CH(CH2)7COOH 18:1 Oleic Cis 9-octadecenoic ω9 282.47 16.3 CH3(CH2)7CH=CH(CH2)7COOH 18:1 Elaidic Trans 9- ω9 Octadecenoic 282.47 45.0 CH3(CH2)7CH=CH(CH2)7COOH 18:2 Linoleic Cis 9, 12- ω6 280.45 -5.0 CH3(CH2)4CH=CHCH2CH=CH(CH2)7CO Octadecadienoic OH 18:3 α-Linolenic Cis 9,12,15- ω3 278.44 -11.3 CH3(CH2)4CH=CHCH2CH=CH(CH2)7CO Octadecatrienoic OH 18:3 γ-Linolenic 6,9,12- ω6 CH3(CH2)3(CH2CH=CH)3(CH2)4COOH octadecatrienoic 20:4 Arachidoni 5,8,11,14- ω6 - 304.47 CH3(CH2)3(CH2CH=CH)4(CH2)3COOH c Eicosatetraenoic 49.5 20:5 EPA 5,8,11,14,17- ω3 - Eicosapentaenoic 54.4 22:6 4,7,10,13,16,19- ω3 - DHA Docosahexaenoic 44.5  Other Lipids: Phospholipids  Oils and fats contain 0.1% - 2.0%  Lecithin extracted from soy beans ▪ High phospholipid content ▪ Used to improve the wettability of powder ▪ Acts as an emulsifier  The uses are based mainly on their amphiphilic properties, due soluble in fat and water → has hydrophilic and hydrophobic properties ▪Remaining part is hydrophobic (non-polar)  Other Lipids: Sterols  Minor component: 0.1% - 0.5%  Principle sterols: ▪ Animal fats: Mainly cholesterol (95% of sterols) ▪ Vegetable oils: Known as phytosterols ▪ β-sitosterol (~50%), campesterol (~33%) & stigmasterol (~4%)  Very non-polar and hence, soluble in oil  Human body needs cholesterol to: ▪ i) make cell membranes, ii) insulate nerves, and iii) produce hormones  Cholesterol issues related to heart disease, is not present in plant systems at a significant level  Commercial Products Containing Phytosterol Phytosterol esters are now being added to spreads at significant levels up to 10% because they are considered to reduce cholesterol levels  Other Lipids: Colouring Compounds 1. Carotenoids  Minor component, typically 5 – 100 ppm  Palm oil has 600 – 1000 ppm  Give yellow to red colour to fats/oils  Highly unsaturated hydrocarbon  Mainly β-carotene  Precursor for formation of vit A in milk 2. Chlorophylls  Greenish tinge to soy bean or olive oil  Are not wanted in refined oils because they produce an undesirable green hue  Level varies according to maturity, source and extraction methods:  Other Lipids: Fat-Soluble Vitamins  Vitamin A ▪ Found in animal fats and not in plants ▪ Plants contains certain carotenoids (provitamin A)  Vitamin D ▪ Derived from sterols ▪ In milk fat, but not vegetable oils ▪ Can be synthesized in the body from a sterol by action of UV light  Vitamin E ▪ Group of compounds known as tocopherols ▪ Rich in vegetable oils, and some in animal fats ▪ Serve as antioxidants Any Questions? Thank you