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Title: Evaluation of enzymatic and non-enzymatic softening in low salt cucumber fermentations

Author
item MARUVADA, RASHMI - NC STATE UNIVERSITY
item McFeeters, Roger

Submitted to: International Journal of Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2009
Publication Date: 4/30/2009
Citation: Maruvada, R., McFeeters, R.F. 2009. Evaluation of enzymatic and non-enzymatic softening in low salt cucumber fermentations. International Journal of Food Science and Technology. 44:1108-1117.

Interpretive Summary: Retention of a firm, crisp fruit texture is a major consideration for pickled vegetables including pickles made from fermented cucumbers. It is known that cucumbers soften rapidly when fermented at low salt concentrations (<3%) without added calcium. This investigation provides evidence that there are both enzymatic and non-enzymatic components to the softening that occurs in low salt fermentation and storage of cucumbers. Enzymes that may be involved in softening are shown to be partially inhibited by high concentrations of salt and calcium chloride. The activity of most of these enzymes is lost within the first week of fermentation.

Technical Abstract: Retention of a firm, crisp fruit texture is a major consideration for pickled vegetables including pickles made from fermented cucumbers. It is known that cucumbers soften rapidly when fermented at low salt concentrations (<3%) without added calcium. This study has shown that there is non-enzymatic softening in low salt fermentations because cucumbers soften even when heated sufficiently to inactivate pectinesterase and several glycosidases that can hydrolyze glycosidic linkages that are present in cell wall polysaccharides. Though pectinesterase activity declines and these glycosidases lose activity within the first week of fermentation there is generally greater loss of cucumber tissue firmness when enzymes are not inactivated by heat. While heating cucumbers prior to fermentation reduces softening during subsequent storage, a heat treatment after two weeks of fermentation does not reduce softening. This result suggested that the enzymatic reactions responsible for softening occur early in the fermentation process even though the softening does not become evident until later in the storage period. Despite the evidence of an enzymatic component of tissue softening in low salt cucumbers, softening could not be associated with specific enzymes.