ARS | Publication request: DEVELOPMENT OF OXIDIZED ODOR AND VOLATILE ALDEHYDES IN FERMENTED CUCUMBER TISSUE EXPOSED TO OXYGEN

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 1999
Publication Date: February 1, 2000
Citation: Zhou, A., McFeeters, R.F., Fleming, H.P. 2000. Development of oxidized odor and volatile aldehydes in fermented cucumber tissue exposed to oxygen. J. Agric. Food Chem. 48:193-197.

Interpretive Summary: Off-odors or flavors in food products can result in large economic losses to food processors and their customers. Development of so-called "oxidized odors" is a common problem in food products, including pickled vegetable products. This work was done to understand the chemistry of the development of oxidized off-odors when cucumbers fermented in low-salt conditions are exposed to oxygen. We identified five compounds that form at parts per billion levels when the fermented cucumber tissue is put in oxygen. The intensity of the off-odor, as perceived by a trained sensory panel of human judges, was strongly correlated with the formation of the five compounds. This result indicated that those specific compounds are the likely cause of the off-odor. Future work will be directed toward finding practical means to prevent formation of the off-odor causing compounds in pickled vegetable products.

Technical Abstract: Changes in volatile compounds in fermented cucumber tissue during exposure to oxygen were investigated by purge and trap sampling, followed by GC-MS. Hexanal and a series of trans unsaturated aldehydes, (E)-2-pentenal, (E) 2-hexenal, (E)-2-heptenal, and (E)-2-octenal, increased in fermented cucumber slurries exposed to oxygen. Sensory evaluation of oxidized odor was correlated with the increase in aldehyde concentrations. Other identified volatile components present after fermentation did not show major changes during exposure to oxygen. Lipoxygenase activity was not detected in fermented cucumbers. There was no decrease in formation of aldehydes in fermented cucumber samples which were heated to inactivate enzymes before exposure to oxygen. These results indicated that formation of aldehydes in oxygen was due to non-enzymatic reactions.