Harvest maturity, storage temperature and relative humidity affect fruit quality, antioxidant contents and activity, and inhibition of cell proliferation of strawberry fruit

The physical qualities, antioxidant content and activity, and antiproliferation activity of ‘Jewel’ strawberry fruit that were harvested at the white tip and red ripe maturity stages and stored in 65 or 95% relative humidity (RH) at 3 and 10 °C for 12 d were studied. Overall quality and firmness of fruit harvested at the red ripe stage declined more rapidly than at the white tip stage, and decreased more rapidly at 10 °C than at 3 °C in fruit of both maturity stages. RH did not affect fruit quality in any treatment. Lightness (L*) and hue angle decreased, and anthocyanin concentrations increased, more rapidly at 10 °C than at 3 °C in the white tip fruit. The L* of red ripe fruit decreased by day 3 and was maintained during the rest of the storage time. The initial anthocyanin concentrations of red ripe fruit were about five times greater than that in white tip fruit and declined during the storage. Total flavonoid and phenolic concentrations, and total antioxidant activity of fruit harvested at the white tip stage were greater than those harvested at the red ripe stage. These differences were maintained during the storage, except for red ripe fruit, where concentrations and activity decreased rapidly by day 12 in fruit stored at 10 °C, especially at 95% RH. Total ascorbic acid concentrations of white tip fruit were lower than in red ripe fruit at harvest, but increased slightly over time, while those in red ripe fruit were relatively stable until they decreased at 10 °C at 12 d. Overall changes of total antioxidant activity were similar to those of total flavonoid and total phenolic concentrations, but not anthocyanin or ascorbic acid concentrations. Fruit quality was correlated with firmness and color attributes as well as with total flavonoid and phenolic concentrations and with antioxidant activity. A 50 g L−1 concentration of strawberry extracts inhibited HepG2 human liver cancer cell proliferation by approximately 80%. The EC50 of antiproliferative activity of strawberry fruit value was not affected by the maturity stage at harvest or by storage temperature.