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Polifenol oksidaz enziminin ısı-ultrason kombinasyonu ile inaktivasyonu sırasında enzimin yapısında meydana gelen değişimin fourier değişim kızıl ötesi (FTIR) spektroskopisi ile incelenmesi

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2013
Bayındırlı, Alev
Baltacıoğlu, Hande
This project was related to understand the conformational changes of PPO after inactivation by heat and heat-ultrasound at different power, temperature and time combinations. The secondary structure change was analyzed by using FTIR spectroscopy and compared with the change in the enzyme activity. When stability of mushroom PPO after heat treatment was investigated, the enzyme remained fully active up to 40oC. There was a slight decrease during the period of 30 min at 40°C; between 50oC and 70°C higher inactivation was achieved and 99% inactivation was detectable at 70°C for 5 min. Furthermore, no activity was observed over 80°C. When the effect of ultrasound on PPO activity was examined, the activities of PPO dropped slightly during the period of 30 min at 20°C after ultrasound treatment, higher PPO inactivation was observed after treatments between 30 and 60 °C with ultrasound. In thermosonicatiion, residual enzyme activity decreased with increasing amplitude, time and temperature. Similar trend was also observed for 80 and 60% amplitude ultrasound treatment. In contrast, it was observed that the remaining enzyme activity increased with decreasing amplitude. When the second derivative spectra was investigated in order to determine the effect of heat and ultrasound treatment on the secondary structure of the enzyme, it was observed that applied heat treatment and thermosonication caused an irreversible change on the secondary structure of the enzyme. However, thermosonication seemed to be more effective on the secondary structural change compared to the heat treatment. In conclusion, enzyme inactivation by combination of heat and ultrasound treatment can be said to be more effective than heat treatment. The result of this study is thought to reference for the similar studies related to the application of ultrasound for enzyme inactivation and can make a significant contribution for the industrial application of ultrasound for enzyme inactivation.