Dragon Fruit and Durian - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 569

indices include soluble solids content (SSC), titratable acid-
ity (TA), and a minimum of 32 days from flowering (Paull,
2004). Generally, SSC or TA alone is not a good measure
of maturity but a SSC:TA ratio of 40 has been suggested
as an optimum harvest index by Paull (2004). The physical
and chemical properties of white- and red-fleshed dragon
fruit, as reported by Wichienchot et al. (2010), are shown
in Table 30.2.
Wanitchang et al. (2010) reported that nondestructive
parameters could be used to predict the maturity indices
of red-fleshed dragon fruit such as number of days af-
ter fruit set (DAFS), with relatively high levels by partial
least squares regression analysis. These authors further re-
ported that with a multivariate maturity index, created from
the original destructive parameters and DAFS by princi-
pal component analysis, the prediction performance was
improved.
For dragon fruit grades and sizes, no US or international
standards have been established (Paull, 2004). Generally,
fruits are graded by size and color. Size grades for Viet-
nam (Le et al., 2000a) are “extra large” ( 500 g; 1.1 lb),

“large” (380-500 g; 0.84-1.1 lb), “regular” (300-380 g;
0.66-0.84 lb), “medium” (260-300 g; 0.57-0.66 lb), and
“small” (

>

260 g). Paull (2004) reported that fruit exported
from Israel to Europe is graded by number of fruits as 6, 8,
10, 12, 14, or 16 per 4 kg (8.8 lb) cardboard box.

<

Postharvest physiology and pathology
Dragon fruit is a nonclimacteric fruit with a very low ethy-
lene production rate of 0.03-0.09 μ l/kg/hr. As is the case for
some other fruits, ethylene treatment does not induce any
color development in dragon fruit (Nerd and Mizrahi, 1999;
Le et al., 2000b). Maximum respiration rate for dragon fruit
occurs during early stages of fruit growth; a respiration rate
range of 75-144 mg CO 2 /kg/hr at 20 ◦ -23 ◦ C has been re-
ported (Nerd and Mizrahi, 1999; Le et al., 2000a).
Le et al. (2000a) reported that chilling injury, mechani-
cal injury, and water loss are the three main postharvest
disorders. Nerd and Mizrahi (1999) reported that flesh
translucency is a symptom of chilling injury; other typical
symptoms include softening, wilting, darkening of scales,
browning of outer flesh, and poor flavor. These symptoms
rapidly develop on fruit held at 6 ◦ C or 42.8 ◦ F for 2 weeks
then transferred to ambient temperature (Nerd and Mizrahi,
1999). Early harvested fruit (25 days from flowering) was
shown to be more sensitive to chilling injury than that which
was harvested 30-35 days after flowering (Paull, 2004).
Mechanical injury leads to the development of sunken ar-
eas on fruit surfaces. More mature fruit is susceptible to
mechanical injury (Le et al., 2000a). It has been reported

Figure 30.1. Dragon fruit tree (top), fruit (middle),
and red- and white-fleshed cut fruits (bottom). For
color detail, please see color plate section. For color
detail, please see color plate section.

2010). The common varieties of dragon fruit with their
fruit/flesh characteristics are listed in Table 30.1.

Harvesting, grades, and sizes
The dragon fruit is harvested manually. Nerd and Mizrahi
(1999) reported that the commonly used index of matu-
rity is skin color change to almost full red; other harvesting