Phytochemicals content and antioxidant properties of sea buckthorn (Hippophae rhamnoides L.) as affected by heat treatment – Quantitative spectroscopic and kinetic approaches

The effect of thermal processing (50-100°C) on the degradation of the phytochemicals in sea buckthorn extract was investigated using chromatographic, fluorescence and FT-IR spectroscopy techniques and degradation kinetics. Heating the sea buckthorn extract resulted in structural changes that led to red- or blue-shifts in maximum emission, depending on temperature and excitation wavelengths. The attenuated total reflectance analysis of the sea buckthorn extract revealed a satisfactory thermostability of compounds at high temperatures. A fractional conversion kinetic model was used to describe the mechanism of degradation in terms of rate and activation energy. Activation energies for total carotenoids, polyphenolic, flavonoids, and antioxidant activity were 8.45±0.93kJ/mol, 2.50±0.66kJ/mol, 22.50±7.26kJ/mol and 15.22±2.75kJ/mol, respectively. The kinetic parameters evidence a higher thermal stability of carotenoids and polyphenols, suggesting higher degradation rates for flavonoids and antioxidant activity. Our results demonstrate that industrial process optimization in terms of time-temperature combinations demands product specific kinetic data.