Ripening and postharvest behaviour of fruits of two Hylocereus species (Cactaceae)

Fruit growth and ripening, and the effect on fruit quality of various storage temperatures, were studied with Hylocereus undatus and Hylocereus polyrhizus plants growing in Beer-Sheva (Israeli Negev desert) under greenhouse conditions. Fruit growth was sigmoidal with a strong decline in growth rate after the onset of peel colour change. The first change in peel colour was recorded 24-25 days after anthesis in H. undatus and 26-27 days in H. polyrhizus. In both species, the peel turned fully red 4-5 days after the first colour change (mean temperature for the study period was 26.6 ± 2.1°C). The slow growth phase was characterised by a decrease in the proportion of peel and concomitant increase in that of pulp, increase in the concentration of soluble solids and soluble sugars and a decline in firmness and the concentration of starch and mucilage. The surge in acidity prior to colour change indicated the beginning of the ripening processes. For H. polyrhizus, which has a red-violet pulp, the increase in pulp pigment paralleled the development of peel colour. Fruits were non-climacteric, and when harvested at close to full colour, they retained market quality for at least 2 weeks at 14°C or 1 week at 20°C. Storage at 6°C is not recommended, because transfer from that temperature to room conditions caused fruits to lose their firmness and flavour rapidly.