Extraction and clarification of apple juice with polygalacturonase obtained from apple (Malus domestica) fruits deteriorated by Aspergillus niger

Abstract

Pectinase is used commercially in the clarification and extraction of fruit juice from different fruits. Green apples and Red apples obtained from the fruits section of a supermarket, Idiroko road, Ota were surface sterilized and inoculated with Aspergillus niger. The stock culture was subcultured on Sabouraud Dextrose  agar plates and 72-hr-old culture of Aspergillus niger served as the inoculum. The fruits were incubated for twenty-five days at room temperature (25 °C). Control fruits were similarly treated except that sterile inoculum was used for the inoculation. Extracts from the inoculated fruits exhibited appreciable polygalacturonase activity while those from the uninoculated fruits possessed only traces of the enzyme activity. The polygalacturonase obtained after enzyme extraction was applied to freshly ripe apple fruits under controlled experimental conditions to investigate the role of polygalacturonase in the production of apple juice. The juice in the cylinder to which polygalacturonase was added was visually clearer  and more than that with distilled water. The optimum temperature of incubation for the clarification of apple fruits with polygalacturonase obtained from apple fruits deteriorated by Aspergillus niger was 25 °C.