Ethanolic Fermentation of Carrot Root Shreds under Low Oxygen

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  • 1 1Dept. of Bioresouce Science, Fac. Agriculture, Kagawa Univ., Kagawa 761-07, Japan
  • 2 2Beltsville Agricultural Research Center, USDA–ARS, Beltsville, MD, 20705

Although a number of studies have been conducted to evaluate the effect of control and modified atmosphere on the quality and storability of carrot roots (Daucus carota L.) under low O2 atmosphere, little is known about the underling biochemical changes in particular changes in anaerobic respiration. Carrot root shreds were stored under a continuous flow of 0.5% and 2% O2 (balance N2), or air for 7 days at 5 and 15°C to study the regulation of glycolysis and the accumulation of glycolytic end products, such as ethanol and/or lactic acid. Low O2 atmosphere caused increases in the concentrations of ethanol and acetaldehyde and the activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC). By day 3, ethanol increased 38-, 25-, 13-, and 9.5-fold, acetaldehyde increased 20-, 13-, 7.7-, and 5.6-fold, ADH increased 7.6-, 6.3-, 3.8-, and 2.7-fold, and PDC increased 4.2-, 3.9-, 2.3-, and 2.2-fold for 0.5% O2 at 15 and 5°C, 2% O2 at 15 and 5°C, respectively, compared with corresponding air control. These results shows that the production of ethanol was higher in 0.5% O2 than in 2% O2 at both temperatures. The enhancement of the glycolytic flux under 0.5% O2 indicates that under these conditions the mitochondrial terminal oxydases were restricted, hence, the enhancement of ethanol synthesis, to compensate partly for the decrease in ATP production.

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