Sistema antioxidante de copo-de-leite submetido à baixa temperatura

Abstract

Cooling is one of the most effective techniques for maintaining the quality and durability of cut flowers, which are essential factors in the marketing of these products. Both quality maintenance and increased durability are dependent on plant metabolism factors. Thus, the objective of this study was to evaluate the effect of low temperature on pre-cooling and storage, on the metabolism of calla lily (Zantedeschiaaethiopica (L.) K. Spreng) by the evaluation of the antioxidant system and levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA).Therefore, the first experiment consisted of the post-harvest evaluation of calla lily under two storage temperatures: 4 °C (cold room) and 21 °C. The activity of catalase (CAT) and superoxide dismutase (SOD) was increased with storage at low temperature (4 °C), as well as durability in the commercial standard (approximately 12 days). For storage at 21 °C, the content of H2O2 and MDA was higher and the visual quality reduction of the inflorescences was more accelerate. Thus, the low temperature leads to a higher activity of the enzymes of the antioxidant system (CAT and SOD) and yields greater post-harvest longevityfor calla lily. The second experiment consisted of the application of the pre-cooling technique (cold room at 4 °C) for different periods (0, 2, 6, 12 and 24 hours), followed by storage of floral stems at 21 °C. The inflorescences were visually evaluated and the plant material was extracted in several collections at 9 time intervals during storage to analyze the activity of the enzymes CAT and SOD, and the levels of H2O2 and MDA. Pre-cooling did not influence the visual quality and longevityof calla lily. SOD activity was related to the low temperature. Higherexposure periods to low temperature, with 12 and 24 hours of pre-cooling, besides the temperature difference in relation to storage at 21 ºC, caused stress, evidenced by the high levels of MDA and high CAT activity. Shorter exposureperiods to low temperatures during pre-cooling resulted in better antioxidant system activity and lower levels of MDA.