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  • Author or Editor: Anthony Kilili x
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`Beauregard' sweetpotatoes (Ipomoea batatas L. Lam) were stored under a continuous flow of 0%, 1%, 1.5%, 2%, 5%, 10%, or 21% O2 (balance N2) for 14 days. Respiration rate was significantly lower at 1.5%, 2%, 5%, and 10% O2 compared with 21% O2, while respiration at 0% and 1% O2 was higher than at 1.5%, 2%, 5%, and 10% O2. Respiration rate at 0% O2 remained high for several days after exposure to air while that at 1.5%, 2%, 5%, and 10% O2 increased rapidly to equal that of 21% O2. Ethanol and acetaldehyde accumulated rapidly at 0% and 1% O2 but were lower at the other O2 levels. Ethanol increased 16- and 4-fold after 14 days of storage at 0% and 1% O2, respectively, compared to 21% O2. In addition, acetaldehyde increased 11- and 8-fold at 0% and 1% O2 respectively, compared to 21% O2. Sucrose and total sugar concentration increased under low O2 concentration while reducing sugars (fructose and glucose) and pH decreased.

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`Beauregard' sweetpotato (Ipomoea batatas L. Lam) roots were maintained under different controlled atmospheres ranging from 0% to 21% O2 at 22 °C in two separate trials for 14 days to study changes in activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH). Trial I showed no difference in activities of PDC and ADH between 0% and 1% O2, or among 2%, 5%, and 21% O2. Both PDC and ADH activities were significantly higher at 0% and 1% O2 compared to the 2%, 5%, and 21% O2 atmospheres. In trial II, both enzyme activities were lower at 1.5% O2 than at 0% O2, but higher than at 10% and 21% O2 atmospheres. The combined data of the two trials showed a very strong correlation between PDC and ADH activities (R 2 = 0.86). In addition, a strong correlation existed between PDC activity and acetaldehyde concentration (R 2 = 0.95). The maximal activities were at pH 6.5 for PDC and at pH 8.5 for ADH in the direction of acetaldehyde-to-ethanol. The results suggest that 1.5% O2 is the critical point for the transition from aerobic to anaerobic metabolism in CA storage of sweetpotato roots, and PDC is the key enzyme in alcoholic fermentation.

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