Anthocyanins and polyphenol oxidase from dried arils of pomegranate (Punica granatum L.)

Anthocyanins are natural pigments responsible for red, purple, and blue colouration in plants. Human consumption of anthocyanins is increasing because of the rising awareness and interest in their potential health benefits. Pomegranate is one of the major sources of polyphenolic phytochemicals, such as anthocyanins. Dried pomegranate raisins (anardana) are consumed in large quantities in Asian countries, and contain substantial amounts of anthocyanins. Five anthocyanins were found to be present in pomegranate raisins. Drying adversely affected the amount of anthocyanins, with polyphenol oxidase (PPO) playing a possible role in oxidative degradation of anthocyanins. Anthocyanins are heat-stable compounds, and inactivation of PPO by processing at high temperature for short periods may prevent PPO-catalysed anthocyanin oxidation in pomegranate arils. Pomegranate PPO kinetics were partially characterised by investigating the effect of substrate (catechol) concentration; optimum pH for PPO activity was found to be 6.0.