Annals of the University Dunarea de Jos of Galati. Fascicle VI: Food Technology (Nov 2018)
Investigations on thermal degradation of Prunus spinosa phytochemicals by fluorescence spectroscopy and inactivation kinetics
Abstract
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°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°C, followed by 3-8 nm red-shift at 70°C and 80°C and again a 2 nm blue-shift at 90°C, when excited at 270 nm. 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 heatinduced 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 Ea value demonstrated a higher stability of flavonoids at lower temperatures, while a faster degradation rate was observed at higher temperatures.
