Effect of water activity on browning reaction in chicken extract = ผลของวอเตอร์แอคทิวิตีต่อปฏิกิริยาการเกิดสีน้ำตาลในสารสกัดจากเนื้อไก่


หญิงไท รัตนมูสิก


วิทยานิพนธ์. (2012) 87 หน้า



The effect of water activity (0.95, 0.85 and 0.75) on Maillard reaction in chicken extract was investigated. Brown color formation and reactant consumption (reducing sugar and free amino acids) were monitored under heat treatment at four temperatures (60, 80, 100 and 120 °C ) and various time intervals (0, 5, 10, 15, 20, 30, 60 min). Chicken extract was heated in a hermetically sealed stainless steel tube and kept at a constant temperature. Reducing sugar and free amino acid concentrations were determined by high performance liquid chromatography (HPLC). Brown pigment was determined by spectrophotometric measurement at 420 mm (A420). The results indicated the presence of glucose as a reducing sugar and seventeen amino acids in the chicken extract sample. During heating glucose concentration dramatically decreased, while brown pigment formation increased when the heating temperature and time increased. At a temperature of 60 °C, aw did not significantly affect the loss of glucose and brown pigment formation (p>0.05). However, at temperatures higher than 60 °C, aw significantly affected the loss of glucose and brown pigment (p<0.05). The maximum brown pigment and minimum glucose contents were observed at aw 0.85. As free amino acid contents remained almost constant throughout the study, it was assumed that free amino acids were present in excess and glucose was a rate determining reactant for color formation via Maillard reaction. Multiresponse modelling technique was used to test the kinetic reaction. A first-order reaction in series model could be used to describe brown pigment formation and glucose loss in chicken extract during heating. An increase in the heating temperature led to higher values of the rate constants of glucose loss and brown pigment formation. Temperature dependence of the reaction rates could be described by the Arrhenius equation. The estimated activation energy (Ea) Values of glucose consumption at aw 0.95, 0.85 and 0.75 were 56.41, 74.82 and 73.53 kJ/mol respectively, while Ea values of brown pigment formation were 4.14, 19.06 and 18.32 kJ/mol, respectively. Water activity dependence of the activation energy (Ea) and frequency factor (ko) was represented by the second order polynomial equations. The kinetic model was validated using another set of experimental data at aw 0.8. The results showed that P(%) for glucose loss and brown pigment formation at aw 0.8 at the temperatures of 60, 80, 100 and 120 °C were within the range of 0.6-19.93 and 1.58-12.39, respectively