Food Chemistry Chapter 17 in Green / Damjii F.2: FATS AND OILS

Read F2 – Fats and Oils - pp Do Q 7-11 on p 491 Homework

F.2: Fats and Oils F.2.1: Describe the difference in structure between saturated and unsaturated (mono- and poly-unsaturated) fatty acids Remember… 3 molecules of fatty acids react with 1 molecules of glycerol to form a lipid

F.2: Fats and Oils F.2.2: Predict the degree of crystallization (solidification) and melting point of fats and oils from their structure, and explain the relevance of this property in the home and in industry.

F.2: Fats and Oils Melting point and hardness (degree of crystallization) depend on – Length of hydrocarbon chain Longer chain = greater molar mass = more vdW forces = higher mp – Degree of unsaturation More double bonds = crooked chains = less contact = fewer vdW forces = lower mp – Cis or trans conformation more cis = more crooked chains = less contact = fewer vdW forces = lower mp more trans = less crooked chains = more contact = more vdW forces (compared to cis) = higher mp

Triglycerides SATURATED (no double or triple bonds) – Tend to be SOLIDS at room temperature – Tend to come from animal products – “Fat” – Examples: Coconut oil Butter lard

Triglycerides Unsaturated (has one double or triple bond) – Tend to be LIQUIDS at room temperature – Tend to come from plant material – “Oil” – Examples Olive oil Canola oil Peanut oil Polyunsaturated (has multiple double or triple bonds) – Example Sunflower oil Corn oil Fish oil

F.2: Fats and Oils F.2.3: Deduce the stability of fats and oils from their structure. Unsaturated – More reactive, less stable – C=C double bond reacts with oxygen (auto- oxidation) Especially in sunlight (photo-oxidation) Margarine gets discolored – Hydrogenation – Degradation by microbes

F.2: Fats and Oils F.2.4: Describe the process of hydrogenation of unsaturated fats. Hydrogenation Addition of hydrogen – high pressure – Temp ~ 200 C – Nickel catalyst

F.2: Fats and Oils F.2.5: Discuss the advantage and disadvantages of hydrogenating fats and oils. A hydrogenated product is –more saturated… or fully saturated… –semi-solid or solid… Advantages of a hydrogenated product is – Form is more convenient for some cooking techniques – More stable (rate of oxidation is decreased) – Texture can be controlled ( hardness / plasticity) can be controlled

F.2: Fats and Oils Disadvantages: …. health related Mono- and poly-unsaturated are healthier for the heart than saturated fat. Partial hydrogenation can form trans-fats – trans-fats don’t occur naturally – difficult to metabolize – accumulate in fatty tissues of body – Increase levels of LDL chloesterol (associated with atherosclerosis… strokes… heart problems)

What is this? Olestra – a fat substitute that is not digested by the body Copyright © 1997 by Daniel J. Berger. alphysiology/websites/2005/castle/page2.htm&usg=__Cs_ytB4MhyvgZs-tnVxiYR1rCrM=&h=360&w=341&sz=16&hl=en&start=11&um=1&itbs=1&tbnid=24- OiiaHITJTsM:&tbnh=121&tbnw=115&prev=/images%3Fq%3Dunsaturated%2Bfat%2B(ester)%26um%3D1%26hl%3Den%26safe%3Dactive%26rlz%3D1R2RNTN_enUS347%26tbs%3Disch:1