| Chocolate bars have become increasingly gourmet in the types of chocolate used and addition of a variety of inclusions such as nuts, fruits, and cereal grains. These factors all have marked impacts on shelf life, as do storage conditions and handling. Understanding interactions among ingredients is crucial for developing improved approaches to maximize shelf life and maintain quality of chocolate products over time.;The most noticeable defect in chocolate is bloom, which presents itself as a white haze on the chocolate surface. Bloom is inevitable over time, but the goal is to prolong its onset as long as possible. One of the many theories proposed to explain the complex phenomenon of bloom is that migration of incompatible fats, specifically from nuts, imposes a second crystal phase, dissolves some cocoa butter, and causes a rearrangement of cocoa butter crystals to highly structured, high melting point forms that deposit on the chocolate surface. Nuts readily develop rancidity and introduce off-flavors into chocolate. Migration of oil from nuts also affects the chocolate matrix itself, altering snap, molding, and gloss as well as crystal form and texture stability. Although nuts are extensively added to chocolate as inclusions, very little basic research has focused on how different nuts affect chocolate properties and stability.;To provide a base of fundamental information that can be applied to improving a wide variety of chocolate products, this study follows migration of oils from roasted monounsaturated almonds and polyunsaturated walnuts into dark chocolate with and without anhydrous milk fat as a crystallization modifier. Oil migration kinetics, nut fatty acid and antioxidant profiles, as well as chocolate melting patterns, crystal forms and shifts, texture properties (snap), bloom, lipid oxidation products and oxidative storage stability, and sensory qualities are being measured to determine the major failure mode (texture, flavor, or bloom) in chocolate. Current industry theories are based primarily on unsaturation and oxidative instability of nuts, but there is little data available. An investigation of nut fatty acid profiles and effects on chocolate crystallization may offer new ways to use nuts that previously have been avoided. |
