Effect of drying on anthocyanins and polyphenol oxidase (PPO) enzyme in pomegranate (Punica granatum L.) arils

Flavonoids including anthocyanins have been reported to act as anti-inflammatory, cardio-protective, anti-neoplastic and anti-viral agents and their bioactivities have been mainly attributed to their strong anti-oxidant properties. A good amount of evidence suggests that consumption of flavonoids is associated with lower incidences of cardiovascular diseases.

Polyphenolic phytochemicals are thought to be chemically unstable, having many isoforms and structural features usually correlate to their bioactivities. Polyphenol oxidase (PPO) enzymes are responsible for the browning reactions in various fruit and food products as they catalyze the oxidation of polyphenols to respective melanins.

Pomegranate (Punica granatum) contains various polyphenolic constituents and has been studied for its anti-oxidant properties. Little is known about the effect of drying and processing on anthocyanin and PPO activity in this fruit which prompted us to propose this comparative study. Dried pomegranate raisin Anardana, which is commercially-available in many Midwestern countries and is used widely in Asian cuisine, has not been tapped for its nutraceutical value. Anthocyanins have been found to be heat stable and results suggest that PPO is the primary enzyme responsible for oxidative degradation of anthocyanins in dried arils. Also the intact cellular matrix was found to be protective in anthocyanin oxidative degradation.