Effect of blanching treatment on antioxidant activity and color values of sugarcane juice

Abstract

Sugarcane is largely grown for manufacturing of table sugar, jaggery and khandsari sugar. Sugarcane juice is a popular natural beverage in India due to its thirst quenching property. It is an instant source of energy and has significant antioxidant activity. The quality and shelf life of sugarcane juice is often judged by its natural yellowish-green color, however enzymatic degradation of this color reduces the acceptability. Enzymatic browning also plays an important role in decreasing the antioxidant activity of juice which is the result of activities of polyphenoloxidase (PPO) and peroxidase (POD). The objective of this research investigation is to study the relation between enzymatic browning and natural antioxidant properties of sugarcane juice. The contribution of PPO is more than POD in browning of sugarcane juice and it is oxygen dependent reaction. To inactivate both PPO and POD before extraction of juice to arrest the browning process completely, fresh sugarcane stalks of Co86032 variety were blanched at 80 °C for different time intervals. The blanching process was optimized according to the color value of extracted sugarcane juice measured by using a tintometer. Enzyme activity of peroxidase and polyphenoloxidase of sugarcane juice extracted from blanched and unblanched cane stalks were measured. Sugarcane juice extracted from unblanched cane stalks showed quick degradation of its natural color resulting into high color values whereas the juice extracted from blanched cane stalks showed better retention of the natural yellowish green color. Antioxidant activity (measured by DPPH method) of sugarcane juice extracted from blanched cane stalk was significantly high as compared to the juice extracted from unblanched cane stalk. Thus, blanching treatment given to the cane stalks before extraction of sugarcane juice was found to preserve the natural yellowish green color and the antioxidant activity of sugarcane juice by inactivating PPO and POD enzymes.