Effects of Oxygen and Turmeric on the Formation of Oxidative Aldehydes in Fresh-Pack Dill Pickles
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Date
2004-04-07
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Abstract
Oxidative off-flavors can develop in pickle products that are exposed to oxygen. Plastic containers, which are becoming more common in the pickle industry, can allow oxygen to migrate into the containers during storage. Pickled cucumber products have been colored for many years using the spice turmeric. The color in turmeric is a result of the presence of the phenolic compound curcumin, which is also a natural antioxidant. Therefore, the objectives of this research were to determine the effect of oxygen concentration on the formation of aldehydes, and to determine if turmeric, at levels suitable for use in pickle products, would be effective in inhibiting the formation of oxidative aldehydes in cucumber pickles. Aldehydes were monitored using purge and trap, and gas chromatography-mass spectrometry (GC-MS). Hexanal, pentanal, 2-hexenal, and heptanal were detected and quantified, and were used as indicators of oxidative off-flavor formation.
Commercial fresh-pack dill pickles from several processors were analyzed for oxidative aldehydes at the beginning and near the end of their expected shelf life. Hexanal, pentanal, and heptanal were identified and quantified in all commercial samples tested. Mean total aldehyde levels declined from 305 to 202 ppb between the short and long term storage samples. In the laboratory, acidified cucumbers were prepared in an anaerobic hood and then injected with increasing amounts of oxygen to determine the effect of oxygen on the formation of oxidative aldehydes. There was a positive linear correlation between the amount of oxygen injected and the formation of the aldehydes hexanal, pentanal, and heptanal. In anaerobic treatments with no added oxygen, there was still development of oxidative aldehydes, with particularly high levels (~800 ppb) of pentanal after 4 days. Regardless of the amount of oxygen that was injected, pentanal declined between 4 and 28 days of storage while hexanal and heptanal concentrations increased in treatments that had oxygen injected. Finally, fresh-pack dill pickles were made and packed in glass containers. Oxygen and different concentrations of turmeric were added to the pickles and the formation of aldehydes was monitored over a 10-week storage period. Turmeric was found to retard formation of hexanal and other aldehydes, specifically pentanal, 2-hexenal, and heptanal, with greater effectiveness as turmeric concentration increased from 16 to 250 ppm. Dill spices were also found to reduce formation of aldehydes. Turmeric was determined to be an effective antioxidant at concentrations appropriate for coloring in pickles. With a level of oxygen comparable to that which would enter a plastic container during a one-year storage period, turmeric maintained hexanal levels near concentrations found in commercial fresh-pack pickles packaged in glass containers.
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Keywords
pickles, cucumber, antioxidant, curcumin
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Degree
MS
Discipline
Food Science
