1. Lipid Oxidation FDSC400

2. Types of Rancidity Hydrolytic rancidity –Lipase –Free fatty acids provide aroma Oxidative rancidity –Radical oxidation –Aldehydes and other compounds provide aroma

3. Oxidative Rancidity Part 1: Form lipid hydroperoxides Part 2: Break down lipid hydroperoxides

4. Oxidative Rancidity Initiation –A radical is formed Propagation –Radicals react and transfer their unpaired electron to other compounds Termination –Two radicals combine to stop the reaction

5. The Pentadiene Structure RHR H. …Radical Migration

6. Addition of Oxygen - Propagation - R+O 2 ROO ROO +RHROOH+R.... Each methylene interrupter can lead to three possible lipid hydroperoxides!

7. Termination

8. Part 2: Hydroperoxide Breakdown (1) (2)

9. Factors affecting rate Fatty acid composition Temperature Water activity Metal ions Oxygen Light

10. Antioxidants Metal chelators citrate, EDTA Radical scavengers (primary and secondary) BHA, BHT, tocopherol

11. Radical Scavenging Antioxidants

14. e.g.:  3 PUFA Supplemented Yogurt w3 oil water w3 emulsionmilkCulture ingredients Pasteurize Homogenize Pack Ferment Store Pasteurize Store/ship Homogenize