Potential role of native pickling cucumber polygalacturonase in softening of fresh pack pickles

This study examined the potential involvement of polygalacturonase (PG) in commercial pickling cucumbers on gradual softening of refrigerated and pasteurized fresh pack pickle products that adversely affects their market-life. PG activity was detected in all sources of commercial pickling cucumbers and refrigerated pickle spears, and activity was detected in some sources of pasteurized spears. Polygalacturonic acid hydrolysis determined from changes in fluidity, reducing groups and oligogalacturonides indicated involvement of both exo- and endo-PG. Treatment of pasteurized pickle mesocarp tissues with concentrated extracts from pickling cucumbers resulted in rapid softening and alteration of pectic substances. D-values for thermal inactivation of pickling cucumber PG at 75, 80, 85, and 90 °C were 22.0, 19.5, 14.5, and 4.2 min, respectively, indicating that residual activity would be expected in commercially pasteurized pickle products. It is concluded that residual cucumber PG could be responsible for softening of processed pickle products, and it is suspected that variations in textural quality of given products are caused by differences in residual types and levels of native PG.

Since enzyme extracts from commercial pickling cucumbers were demonstrated to be capable of softening pickle tissues and that PG activity was present in some processed fresh pack products, methods that inactivate or eliminate the enzyme(s) should reduce softening of products during storage and marketing.