RESISTANCE TO CHILLING INJURY IN RED, LYCOPENE-ACCUMULATING TISSUE OF COLD-STORED GRAPEFRUITS

Abstract

Grapefruits are widely recognized by their extreme sensitivity to develop chilling injury (CI) during postharvest storage at low temperature. Moreover, many cultivars and mutants of grapefruits exhibit important differences in both external and internal coloration, from yellow to deep red, due to a distinctive accumulation of the red carotene lycopene. Thus, in this study the genetic variability in external peel coloration of grapefruits has been used to examine the potential relationship between carotenoid content and composition, and susceptibility to CI. CI increased progressively after 2 weeks storage at 2°C in fruit of the yellow grapefruit ‘Marsh’ (M) but in the fruits of red cultivar ‘Star Ruby’ (SR) CI symptoms were exclusively restricted to the yellow areas of the peel. Thus, CI was absent in red peel tissue, even after prolonged cold storage, in which lycopene content was about 14-times higher than in yellow tissue. In addition, SR grapefruits growing under shaded conditions developed an intense external red coloration and accumulated large amount of lycopene, and were also highly resistant to CI upon subsequent postharvest cold storage. To further explore the mechanisms involved in the resistance to CI induced by lycopene, total antioxidant activity was determined in yellow and red peel tissue of grapefruit, and the potential relationship between carotenoids and the development of CI is discussed.