MECHANISM OF BROWNING IN FRESH HIGHBUSH BLUEBERRY FRUIT (VACCINIUM-CORYMBOSUM L) - ROLE OF BLUEBERRY POLYPHENOL OXIDASE, CHLOROGENIC ACID AND ANTHOCYANINS

Browning reactions which occurred after crushing fresh blueberries (Va ccinium corymbosum L) were followed by determination of chlorogenic ac id colour density, polymer colour and the level of polymers. A polyphe nol oxidase (PPO) activity plays a dominant role in enzymatic browning . Peroxidase (POD) does not contribute to brown colour formation. The loss of 29% of the colour in a model system containing PPO and blueber ry anthocyanins indicated that PPO could act directly on these pigment s. However, the rate of anthocyanin degradation was stimulated by the addition of chlorogenic acid.