DIFFUSION PLATE ASSAY FOR MEASUREMENT OF POLYGALACTURONASE ACTIVITIES IN PICKLE BRINES

A modified diffusion plate assay was evaluated for its efficacy in measuring polygalacturonase (PG) activities in simulated and commercial cucumber pickle brines. The diffusion plate assay was capable of detecting low PG activities (7 X 10(-5) PG units/mL). Clear zone diameters formed in the diffusion plate assay were highly correlated to changes in specific viscosity obtained by the conventional viscometry assay procedure. Slight, dark-stained zones appeared with an ionic strength of 1. 6 (NaCl) and increased in diameter with increasing ionic strength. Ionic strengths of commercial pickle brines (0. 9-1.8) did not interfere with the diffusion plate assay for detecting PG activity. The diffusion plate assay was observed to be a suitable and convenient alternative to the viscometry procedure for monitoring PG activities in brines used for the bulk storage of pickles.