Physical, Perceptual, and Bioactive Components of Chocolate

298 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006.Chocolate is in essence cocoa mass and sugar suspended in a cocoa butter matrix. Consumers have come to expect the rich, smooth texture and mouthfeel of chocolate, which is due to unique interactions of polymorphic lipid structures of cocoa butter. Various storage conditions may lead to development of either fat or sugar bloom, each of which compromises both visual and textural quality. The initial goal of this research was to evaluate the impact of various storage conditions on chocolate texture. Temperature fluctuations significantly impacted chocolate appearance and texture. Further investigations were conducted on the influence of storage conditions using several instrumental methods to evaluate lipid polymorphism, fat bloom formation, texture and flavor changes, and antioxidant alterations, as well as perceptual changes in chocolate texture and flavor by a descriptive sensory panel. Storage at high temperature with fluctuations increased the rate of polymorphic transition to form VI. Chocolate stored at high temperature with and without fluctuations were harder, more fracturable, more toothpacking, had longer melt time, less sweet taste, and less cream flavor. These samples had significantly rougher surfaces, less grains in a specific area, and a larger grain size. Volatile release was significantly impacted by storage condition, most likely due to increased solid fat content (SFC) during storage at ambient, frozen and high relative humidity, which has been shown to facilitate volatile loss. Storage at high relative humidity significantly reduced antioxidant capacity. Further experimentation determined the impact of cycling temperature and duration on lipid polymorphism, fat bloom formation, and surface characteristics. Dark chocolate cycled at 34°C transitioned to polymorph VI faster and formed fat bloom more rapidly than samples cycled at 30 and 32°C. Temperature cycling at 37°C resulted in a 'memory-free' chocolate that recrystallized in polymorph V and contained 'sugar-cocoa bloom', similar to characteristics of untempered chocolate. Based on this research, if long-term storage cannot be avoided, it is recommended that chocolate be stored in its original wrapper at frozen temperature (-27.2°C) without fluctuations.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD