Development and characterization of nem enzyme type time-temperature indicator

Time temperature indicators (TTI) are small devices that show time-temperature dependent, easily measurable and irreversible change, that can be correlated to quality changes of food undergoing the same time-temperature exposure. It is necessary to develop new, cheap and biological indicators to apply this system in our country.In this study, mushroom was chosen as a case study and to develop indicator first of all shelf life of the mushroom was determined. In shelf life determination of mushroom, parameters which affect mushroom quality were chosen as color, texture and physical properties. By considering all quality parameters shelf life of mushroom for different temperatures were determined. It was determined that shelf life of mushroom at temperatures of 5, 10, 15 and 25°C are 10, 7, 3 and 1 days, respectively.It was understood that color change of mushroom followed zero order kinetics and k values were determined from the linear slopes of L* versus time graphs. Obtained k values were used in Arrhenius plot and activation energy of mushroom color change was found as 70.8 kJ/mol.Enzymatic time temperature indicator was based on the tyrosinase catalyzed oxidation reaction of L-tyrosine (substrate). Indicator was developed by immobilizing enzyme first and then storing them in the same temperatures of mushroom storage after different concentrations of substrate solutions were added. By using the color changes of indicators during storage, activation energies were determined as 123, 52 and 49 kJ/mol for the substrate concentrations of 0.1, 0.5 and 1 mM, respectively.Activation energies obtained for TTIs with different substrate concentrations were modeled and the substrate concentration should be used to get same activation energy with mushroom was found as 0.25 mM L-tyrosine.Key Words: enzyme, time-temperature indicator, mushroom, shelf life