Symptoms and sensitivity to chilling injury of pitahaya (Hylocereus undatus (HAW.) Britton & Rose) fruits during postharvest
Dragon fruit or pitahaya (Hylocereus undatus (Haw.) Britton & Rose) is an exquisite and exotic fruit with attractive aroma and flavor, and a characteristic red-skinned color. Its production and supply for regional and foreign markets is limited to its storage life. The objective of this study was to evaluate physiological alterations and sensitivity to chilling injuries during postharvest of pitahaya. Fruits harvested at the Tehuacán Valley, Puebla, México, were stored at three postharvest temperatures: 3, 7, and 11±1 °C, for 7, 14, and 21 d and under these conditions plus a 4 d period at 22±1 °C. Evaluated fruits were then contrasted with fresh fruit (control 1), and non-cold stored fruits maintained 4 d at 22 °C (control 2). Variables were epicarp color, fruit firmness, total soluble solids (TSS), titratable acidity, and vitamin C content in the mesocarp; and a maturity index was calculated. The experimental design was completely randomized, with 10 repetitions, where one fruit was the experimental unit. Results were analyzed using ANOVA and treatment means were compared with the Tukey test. In order to recognize symptoms of chilling injury a multivariate data analysis of Principal-Component (PC) was also carried out. Control 1 fruits was red, with relatively low-lightness and bright suitably index of L* 38, hue angle 38 and chroma 39. The color of control 2 fruits significantly changed compared to control 1 (L* 46, hue angle 6, and chroma, 53). Fruit on cold storage maintained color, firmness (5 N), TSS (9.7 °Brix), acidity (0.37 g malic acid g-1 ), maturity index (42 °Brix g malic acid g-1 ) and vitamin C content (0.78 mg 100 g-1 ) partially stable. Changes depending on temperature and time of storage did not follow identifiable trends. Chilling injury in pitahaya fruits does not occur progressively, and is higher under cold and room storage temperature. PC analysis indicated that 7 d of storage partially maintained fruits quality, regardless of the extra 4 d time at room temperature; thus, implying that postharvest handling of pitahaya fruits may extend its shelf life several days.