chapter  4
40 Pages

Surimi Gelation Chemistry

Natural foods, despite their high water content, are made solid by the conning water within the cells. In contrast, fabricated foods with solid-like (visco-elastic) properties are almost always hydrogels (water conned in a polymer matrix). Most gelling carbohydrates and gelatin (protein) form hydrogels when their concentrated solutions are cooled; subsequently, however, these melt upon

4.1 Introduction .......................................................................................................................... 101 4.2 Protein Components of Surimi ............................................................................................. 102

4.2.1 Myobrillar Proteins................................................................................................. 102 4.2.1.1 Myosin........................................................................................................ 103 4.2.1.2 Actin ........................................................................................................... 104 4.2.1.3 Other Myobrillar Proteins of Fish Muscle ............................................... 104 4.2.1.4 Thick Filament Assembly .......................................................................... 106 4.2.1.5 Paramyosin ................................................................................................. 107

4.2.2 Stroma Proteins ........................................................................................................ 108 4.2.3 Sarcoplasmic Proteins .............................................................................................. 108

4.2.3.1 Heme Proteins ............................................................................................ 110 4.2.3.2 Enzymes ..................................................................................................... 111

4.3 Lipid Components of Fish Muscle ........................................................................................ 113 4.4 Heat-Induced Gelation of Surimi Myobrillar Proteins ....................................................... 114 4.5 Bonding Mechanisms during Heat-Induced Gelation of Fish Myobrillar Proteins ........... 116

4.5.1 Hydrogen Bonds ....................................................................................................... 116 4.5.2 Ionic Linkages (Salt Bridges).................................................................................... 117 4.5.3 Hydrophobic Interactions.......................................................................................... 118 4.5.4 Covalent Bonds ......................................................................................................... 119

4.5.4.1 Disulde Bonds .......................................................................................... 120 4.5.4.2 Rheological Behavior of Cross-Linked Protein Gels ................................ 120 4.5.4.3 Role of Disulde Bonding in Myosin/Actomyosin Gelation ..................... 121 4.5.4.4 Covalent Cross-Linking during Setting ..................................................... 121 4.5.4.5 Protein Stability Effects on Setting ........................................................... 125 4.5.4.6 Endogenous Transglutaminase .................................................................. 125 4.5.4.7 Exogenous TGase Addition ....................................................................... 126

4.6 Factors Affecting Fish Protein Denaturation and Aggregation ............................................ 128 4.6.1 Importance of Muscle pH (Acidity) .......................................................................... 130 4.6.2 Frozen Storage Stability of Surimi ........................................................................... 130

4.7 Summary: Factors Affecting Heat-Induced Gelling Properties of Surimi .......................... 130 4.8 Acid-Induced Surimi Gels .................................................................................................... 131 References ...................................................................................................................................... 131

heating (i.e., are thermo-reversible). Surimi, on the other hand, like the muscle proteins of other animal species, as well as egg white, wheat gluten, and milk b-lactoglobulin, forms thermo-irreversible gels upon heating, which do not melt with further temperature change. Furthermore, surimi is known to produce gels of very high strength and deformability. It is the excellent heat-induced gelation properties of surimi that make it useful as a food ingredient. This chapter will review the chemistry of muscle proteins with regard to surimi gelation, as affected by various factors associated with the manufacturing of surimi and surimi seafoods.