chapter  10
_C000 Final Proof page iii 14.2.2008 6:50am Compositor Name: Lipids: Theory and
Pages 30

I. Introduction ....................................................................................................................... 268 II. Lipid Composition ............................................................................................................ 268 III. A Brief History ................................................................................................................. 268 IV. The Four Faces of Interesterification ................................................................................ 269 V. Interesterification Catalysts ............................................................................................... 270

A. Is a Catalyst Necessary for Interesterification? ......................................................... 270 B. Available Catalysts for Interesterification ................................................................. 270 C. Precautions ................................................................................................................ 270 D. The ‘‘Real’’ Catalyst.................................................................................................. 271 E. Reaction Termination ................................................................................................ 271

VI. Reaction Mechanisms ....................................................................................................... 271 A. Carbonyl Addition Mechanism ................................................................................. 272 B. Claisen Condensation ................................................................................................ 273

VII. Random and Directed Interesterification........................................................................... 275 A. Random Interesterification ........................................................................................ 275 B. Batch Interesterification............................................................................................. 276 C. Continuous Interesterification ................................................................................... 277 D. Regioselectivity in Interesterification........................................................................ 277 E. Directed Interesterification ........................................................................................ 278

VIII. Kinetics of Chemical Interesterification............................................................................ 280 IX. Assessing the Effects of Interesterification on Lipid Properties....................................... 280

A. Physical Properties .................................................................................................... 282 1. Cloud Point ......................................................................................................... 282 2. Dropping Point.................................................................................................... 282 3. Nuclear Magnetic Resonance ............................................................................. 283 4. Differential Scanning Calorimetry...................................................................... 284 5. Cone Penetrometry ............................................................................................. 284 6. X-Ray Diffraction ............................................................................................... 284 7. Polarized Light Microscopy ............................................................................... 284

B. Chemical Properties .................................................................................................. 285 X. Applying Interesterification to Food Lipids...................................................................... 286

A. Shortening ................................................................................................................. 286 B. Margarines ................................................................................................................. 286 C. Palm Oil and Palm Kernel Oil .................................................................................. 287

288 E. Fat Substitutes ........................................................................................................... 289

XI. Oxidative Stability ............................................................................................................ 289 XII. Nutritional Consequences of Interesterification................................................................ 290 XIII. Distinguishing Chemical from Enzymatic Interesterification........................................... 291 XIV. Perspectives....................................................................................................................... 291 Acknowledgments......................................................................................................................... 291 References ..................................................................................................................................... 292

Interesterification, hydrogenation, and fractionation are three processes available to food manufacturers to tailor the physical and chemical properties of food lipids [1,2]. At present, roughly one-third of all edible fats and oils in the world are hydrogenated, whereas ~10% are either fractionated or interesterified [3]. Each operation is based on different principles to attain its goal. Fractionation is a physical separation process based on the crystallization behavior of triacylglycerols [4,5]. Hydrogenation, on the other hand, is a chemical process leading to the saturation of double bonds present in fatty acids to harden fats for use as margarine and shortening basestocks. Interesterification, also a chemical process, causes a fatty acid redistribution within and among triacylglycerol molecules, which can lead to substantial changes in lipid functionality. This chapter discusses the application of the theory of chemical interesterification to the production of edible fats and oils.