Pectic Enzymes in the Clarification of Apple Juice

To know the role of pectic enzymes in the clarification reaction of apple juice, a simplified model for apple juice, that is, aqueous re-suspension of ultracentrifugal precipitates of apple juice, was employed. It was found that the precipitates (i.e., suspended materials) contained 36% of protein and that the surface of the suspended materials was negatively charged at pH 3.5. Positively charged colloids at pH 3.5 such as gelatin enhanced the clarification reaction or mutually coagulated with the suspended materials. While negatively charged colloids at pH 3.5, such as sodium alginate completely inhibited the clarification reaction. The direct participation of pectic enzymes in the clarification of apple juice was shown, and a supposed mechanism of the enzymic clarification was presented.