Pitaya (Dragon Fruit)

MATURITY & QUALITY

Maturity Indices

Dragon fruit are generally harvested close to full ripe stage because they do not continue ripening after harvest.  As the fruit matures and ripens, skin color changes to red or yellow, total soluble solids (TSS) increases to a peak, and titratable acidity (TA) as well as flesh firmness start decreasing. The commonly-used maturity indices are days after flowering (minimum of 27 to 33 days, depending on cultivar and production area) and intensity of red or yellow skin color.

Quality Indices

• Fruit size
• Skin color (red, purple, or yellow)
• Absence of defects, including insect damage, skin splitting, mechanical damage, chilling injury, water loss, and decay.
• The flesh can be white (Hylocereus undatus) or various hues of red (Hylocereus polyhizus), depending on the species and cultivar.
• Top quality fruit should be well shaped, have firm, fleshy and green bracts, firm flesh, and a minimum TSS:TA ratio of 40.

TEMPERATURE AND CONTROLLED ATMOSPHERES (CA)

Optimum Temperature

Red pitaya (Hylocereus undatus and H. polyrhizus) and yellow clones of H. undatus: 10ºC (50ºF)

Yellow pitaya (Selenicereus megalanthus): 6ºC (43ºF)

Potential Postharvest Life

4 weeks, depending on growing location and maturity

Optimum Relative Humidity

85-90%

Rates of Respiration

41-79 ml CO₂/kg.h at 20-23ºC (68-73ºF)
To calculate heat production, multiply ml CO₂/kg•h by 440 to get Btu/ton/day or by 122 to get kcal/metric ton/day.

Rates of Ethylene Production

0.01-0.09 µl C₂H₄/kg•h during fruit growth and development. Ethylene production does not increase during fruit ripening. Based on the pattern of CO₂ and C₂H₄ production, pitaya is a non-climacteric fruit.

Responses to Ethylene

Ripening changes in the fruit are independent of ethylene. Ethylene treatment has no effect on the initiation of fruit color development.

Responses to Controlled and Modified Atmospheres

Modified atmosphere studies show that fruit harvested 30 days after flowering and stored in modified atmosphere bags with oxygen, transmission rate of 4 L m^-2 day^-1 for ~5 weeks at 10ºC (50ºF) had less dehydration and scale wilting, and better maintenance of fruit color with greener scales compared to fruit stored without bags at the same temperature. It is unknown how much benefit is due to a modified atmosphere as compared to the higher relative humidity within the bags. More mature fruit and storage at higher temperatures reduces the beneficial effects of modified atmospheres.