Kiwifruit Juice Clarification using a Fungal Proteolytic Enzyme

A commercial fungal proteolytic enzyme from Aspergillus niger was used in kiwifruit juice as a replacement for conventional fining agents to produce a stable clarified juice. Reductions in detectable protein levels of 73% and 82% were achieved using 500 mg/kg of enzyme and incubating at 60°C for 20 and 60 min respectively. Concentrates prepared from proteolytic enzyme-treated juice had reduced browning and haze formation compared to a control, without affecting ascorbic acid level. When stored at 20°C, proteolytic enzyme treated concentrates (60 min) remained clear up to 90 days and had minimal haze (A650 nm= 0.047) and browning (A420 nm= 0.93) after 6 mo storage. The molecular size of the protein as well as protein concentration are important factors in haze formation.