Vol. 80 No: 6

Title:
Changes in sugars and acids in pitaya (Hylocereus undatus) fruit during development

Authors:
K. NOMURA, M. IDE and Y. YONEMOTO

pp: 711-715

Abstract:
Seasonal changes in skin colour, and sugar and acid contents were studied in pitaya (Hylocereus undatus Britt & Rose) fruits pollinated in July (Summer) and October (Autumn) on Ishigaki Island, Japan. Changes in skin colour pattern (a* and b* values), total soluble solids (TSS) and sugar contents exhibited a sigmoid pattern irrespective of the time of pollination, except for skin colour b* values in Autumn-pollinated fruit. In both groups, mature fruit had higher TSS contents in the centre of the fruit compared with other sections. Malic acid was the main acid in the fruit, with no clear seasonal pattern. Changes in glucose and fructose contents exhibited a similar pattern to that of TSS, but the values were higher in mature Autumn fruit than in mature Summer fruit, and differed among fruit sections. The differences tended to converge during late maturation when a* values and TSS contents reached a constant level. These results indicate that each a* value and TSS content could not be applied solely to a maturity index. By considering accumulated temperature (AT) from pollination (AT-growth) instead of days after pollination, changes in a* values and TSS contents were in good agreement, irrespective of pollination date.These values reached a plateau when fruit had received about 22,500°C AT-growth. In both series, the best harvesting time for white pitaya was when fruits had received approx. an additional 3,000°C AT after the a* value had reached a plateau.

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