Selecting fruit quality characteristics to predict optimum harvest time of red pitaya (Hylocereus Polyrgizus) fruit.

• Main Authors: Melly Novita,, Ahmad, Siti Hajar, Ding, Phebe
• Format: Conference or Workshop Item
• Language: English; English
• Published: 2007
• Online Access: http://psasir.upm.edu.my/id/eprint/18982/1/ID%2018982.pdf; http://psasir.upm.edu.my/id/eprint/18982/

This study was carried out to predict optimal harvest time of red pitaya (hylocereus polyhizus) fruit using selected fruit physical and eating quality characteristics. Pitaya fruits were harvested at 5-day interval beginning from 25 to 40 days after anthesis (DAA) and the fruit characteristics were measured. The growing degree days (GDD) were calculated from 5 to 40 DAA. Regression analysis was carried out to study the relationship between fruit characteristics and GDD. The correlation between selected peel and pulp,L*,C*,h⁰,firmness, sugar/acid ratio and flavour were determined for fruits at 483 to 765 GDD. Characteristics that were significantly correlated were used in a forward multiple regression analysis to develop a model to predict optimal harvest time.There were significant relationship between GDD and peel L*,C*,h⁰ with R²=0.90,0.95,0.93, respectively. There were also significant relationship between GDD and pulp *,C*,h⁰ with R²=0.95,0.76,0.92 respectively. Significant positive relationship were also obtained between GDD and sugar/acid ratio (R²=0.92) and flavour (R²=0.97), while significant negative relationship (R²=0.98) occured between GDD and firmness. There were significant correlations between peel L*,C*,h⁰, pulp L* and h⁰. There were also significant correlations between firmness and both peel and pulp L*,C*,h⁰. Sugar/acid ratio was negatively correlated with peel L*, peel h⁰, pulp L* and firmness and positively correlated with peel C*, pulp h⁰ and flavour. Flavour was positively analysis showed 50%and 35% of the variability in sugar/acid ratio was accounted for by peel L* and firmness, respectively (Sugar/acid ratio=480.97 - 8.16 (Peel L*) - 39.57 (Firmness)). The peel C* and firmness accounted for 38% and 35% respectively of the variability in flavour of red pitaya (Flavour = 1.58 - 0.01 (Peel C*) - 0.16 (Firmness). The peel C* and h⁰ accounted for 45% and 51% of the variability in firmness (Firmness = 5.83 - 0.10 (Peel C*) + 0.05 (Peel h⁰). These results suggest that peel C* and h⁰ could be used to predict optimal harvest time of red pitaya.