Agriculture Reference
In-Depth Information
Table 14.7
Commercial Harvest Indices to Maximize Post-harvest Quality for Selected Melons.
Stem abscission
zone
Typical soluble solids
content (°brix)
Total titratable acidity
(% major acid)
Melon type
Fruit shape
Epidermis
Cantaloupe
Round
Fully formed
Green
12-17
—
Honeydew
Round
None
White
9-12
—
Galia
x
Round
Fully formed
Light yellow, some
green
10.8
0.054
Charantais
Round
Fully formed
Smooth sutures
Watermelon
Oblong;
round
None
According to type;
yellow groundspot
9.8 (cv. Millionaire)
0.3 (cv. Millionaire)
Source: Artes
et al
. (1993), Bower
et al
. (2002), Cartaxo (1998), Evensen (1983), Fallik
et al
. (2001) and Lester and
Shellie (1992).
has the highest singlet oxygen quenching capacity in vitro.
Other outstanding features are its high concentrations in tes-
tes, adrenal gland and prostate. In contrast to other carote-
noids, its serum values are not regularly reduced by smoking
or alcohol consumption, but with increasing age. Remarkable
inverse relationships between lycopene intake or serum val-
ues have been observed in particular for cancers of the pros-
tate, pancreas, and to a certain extent of the stomach. In
some studies, lycopene was the only carotenoid associated
with risk reduction. Accordingly, although watermelon con-
sumption may help reduce risk of certain cancers, tomato
has a larger role in risk reduction because of greater per
capita consumption, 165 lb, compared to 17 lb for watermel-
ons (Clinton & Giovannucci 1998; Maynard 2001). The
Food and Agriculture Organization of the United Nations
has compiled a thorough list of the regional data centres that
report nutritional composition of foods (FAO 2002).
harvested either immature or mature, while those consumed
as dessert fruits are always harvested mature during ripen-
ing. Immature-harvested types (e.g., summer squash and
cucumber) are selected for tenderness and characteristic
epidermal and stem colour, and are normally graded dimen-
sionally according to applicable grade standards. Chayote
should be harvested immature firm, with tender, smooth
skin (absence of spines) with natural gloss (Aung
et al
.
1996). Bitter melon is harvested immature, until seed hard-
ening, and should have uniform green colour and freedom
from splitting (sign of over-maturity) (Zong
et al
. 1995).
On the other hand, winter squashes must be harvested
upon reaching physiological maturity or during ripening
when the fruit has reached a minimal level of acceptable
quality. For example, immature-harvested spaghetti squash
(
6 weeks after anthesis), have poor quality when cooked
(Edelstein
et al
. 1989).
Melons and watermelon consumed as dessert fruits have
special harvest considerations (Table 14.7). Netted melons
have climacteric respiratory and ethylene patterns and,
hence, must be harvested after physiological maturity is
reached for proper post-harvest ripening (Larrigaudiere
et al
. 1995). Evensen (1983) found that cantaloupe had
best post-harvest quality and storage life when harvested
with green epidermis and at full-slip (complete formation
of the stem scar); those harvested at half-slip stage
had poorer flavour following storage and ripening. Best
post-harvest quality for honeydew melons was obtained by
sampling for the following parameters at harvest: white
epidermal colour, soluble solids above minimally required
value and typical fruit shape, as determined by length-to-
diameter ratio (Lester & Shellie 1992). Galia-type melons
harvested when background colour became light yellow
(Plate 14.1) had higher soluble solids content and higher
<
POST-HARVEST PHYSIOLOGY
OF CUCURBITS
Quality maintenance from harvest through handling and ship-
ping is crop dependent. In the case of cucurbits, post-harvest
physiology varies widely due to the great number of pheno-
types that are commercially grown around the world. In this
section we will briefly discuss the underlying physiological
factors that affect post-harvest quality. Two comprehensive
reviews have been written regarding post-harvest physiology
of melons (Pratt 1971; Seymour & McGlasson, 1993); another
excellent resource is Rubatzky and Yamaguchi (1997).
Maturity and ripening, and harvest indices
As fruits, cucurbits are harvested at several maturities
(or stages of maturation), depending on the crop and on
the intended market. Those consumed as vegetables are
