INVESTIGATIONS ON THERMAL DEGRADATION OF PRUNUS SPINOSA PHYTOCHEMICALS BY FLUORESCENCE SPECTROSCOPY AND INACTIVATION KINETICS

The present study focuses on the heat-induced structural changes and the degradation kinetics of polyphenolic compounds correlated antioxidant activity from Prunus spinosa fruit extract at temperatures ranging from 60 to 90 degrees C. The influence of heating on anthocyanins was evaluated by using fluorescence spectroscopy technique. The most effective fluorescence intensity was observed at the UV absorption maxima of 300 nm, whereas the extract exhibited a fluorescence emission maximum at 408 nm. By increasing the temperature, a significant decrease in the fluorescence intensity was registered, accompanied by a 12 nm blue-shift at 60 degrees C, followed by 3-8 nm red-shift at 70 degrees C and 80 degrees C and again a 2 nm blue-shift at 90 degrees C, when excited at 270 mn The presence of the chalcone derivative induced by thermal treatment was also suggested. First-order and fractional conversion kinetic models were used to describe the heat-induced changes of the phytochemicals and antioxidant activity in terms of reaction rate constant and activation energy. A higher degradation rate for polyphenols was observed, whereas the antioxidant activity degrades at the lowest rate. The activation energies for anthocyanins, polyphenols, flavonoids and antioxidant activity were 6.95 +/- 1.22, 5.99 +/- 1.20, 42.50 +/- 9.42 and 13.35 +/- 5.01 kJ/mol, respectively. A higher E-a value demonstrated a higher stability of flavonoids at lower temperatures, while a faster degradation rate was observed at higher temperatures.