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  • Author or Editor: Peter Toivonen x
  • Journal of the American Society for Horticultural Science x
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In order to determine the effects that 1-methylcyclopropene (1-MCP) may have on antioxidant metabolism during cold storage, apples (Malus ×domestica Borkh. cv. Golden Smoothee) were treated with 625 nL·L−1 1-MCP immediately after harvest and stored in air for 3 months. Differences in total antioxidant activity and ascorbate levels were determined during storage and related to the activity of the antioxidant enzymes superoxide dismutase [SOD (EC 1.15.1.1)], catalase [CAT (EC 1.11.1.6)], and peroxidase [POX (EC 1.11.1.7)] in pulp. The level of oxidative stress in the pulp tissue was also established by determining changes in levels of hydrogen peroxide and in the content of peroxidative markers during storage. Controls and 1-MCP-treated fruit exhibited similar changes in total antioxidant activity and ascorbate levels. However, significant differences in oxidative stress levels were found between treated and untreated fruit. 1-MCP-treated fruit exhibited lower levels of hydrogen peroxide and significantly lower levels in peroxidative markers, especially at the end of the storage period. In line with this last result, 1-MCP-treated fruit also exhibited greater enzymatic antioxidant potential and, more specifically, a higher level of POX activity. Collectively, these results showed that 1-MCP did not detrimentally affect the antioxidant potential of the fruit and provided evidence to support the hypothesis that the beneficial effects of 1-MCP on ripening are not exclusively limited to its effect on ethylene, but also include direct effects on peroxidation and POX enzyme activity.

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Replacing postharvest moisture loss in carrots (Daucus carota L., `Caro-choice') by single and repeated recharging (rehydration in water) treatments, interaction between the duration of recharging and temperature during recharging, and the effects of these treatments on moisture loss during subsequent short-term storage were studied. Carrot mass gain increased with increase in duration of single recharging treatments. Carrots that had lost 2.96% of their mass during storage at 13 °C and 35% relative humidity regained as much as 83% of the mass during recharging for 12 hours. Longer rechargings had little additional effect. Recharging at 13 °C and 26 °C was more effective at replacing water than at 0 °C. The rate of moisture loss (percent per day) during subsequent storage was not affected by recharging duration and temperature during recharging. With repeated recharging every 3.5 days, increase in recharging duration up to 9 hours increased carrot mass gain. Most of the mass gain occurred following 0 to 7 days of storage. These treatments, however, did not affect the rate of moisture loss during subsequent storage. These results suggest that the beneficial effect of recharging on carrot quality is due to replacement of the lost moisture and not to a decrease in moisture loss during storage following recharging. Abrading increased mass loss in non-recharged carrots and increased mass gain during recharging. Recharging should be explored as an option to improve the shelf life of carrots.

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The market value of the apple (Malus ×domestica Borkh.) cultivar Ambrosia is closely linked to the characteristic blush on the skin surface. For ‘Ambrosia’ orchards that produce consistently low levels of surface blush, the implementation of reflective rowcovering has improved surface coloration, but the reflected wavebands responsible for this enhanced color production have not been confirmed. This study consisted of two separate experiments: one conducted in the field to confirm reflective rowcovering efficacy and the other in a controlled environment cabinet to determine which waveband was enhancing red blush production. The red blush production in orchards with and without reflective rowcovering was then directly compared with the red blush produced on the surface of apples that were poorly colored at harvest and then exposed to visible, fluorescent, ultraviolet A (UVA), or ultraviolet B (UVB) light sources within the controlled environment chamber. Consequent analysis of the red blush color within the Commission Internationale de l’Eclairage a* and b* color space was conducted to evaluate the quality of the red blush pigment under each treatment in the field and the controlled environment chamber. The analysis revealed that the red blush that developed on apples from the reflective rowcover treatment most closely matched the red blush that developed in response to UVB exposure in the controlled environment cabinet. Further analysis of gene expression and anthocyanin contents in the ‘Ambrosia’ apples support the hypothesis that the primary driver for the characteristic red blush development, when reflective rowcovers are used, is increased exposure to UVB light.

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