Agriculture Reference
In-Depth Information
Maturity indices and harvesting
Maturity at harvest
Generally, watermelons are harvested before the fully ripe
stage if they are intended for shipment to distant markets.
In ripe fruit, the placental tissue can become quite soft,
especially if the production environment is cloudy or wet.
By harvesting about 4 days before full ripeness, placental
texture is firmer, and red color will continue to develop.
Unripe fruit often has a “green” flavor associated with the
flavor volatile hexenals (Beaulieu, 2006a). Overripe fruits
are avoided as the texture is usually soft, the color may
change from red to orange-red, and flavor may be more
like squash or pumpkin, originating from C
9
aldehydes
(Rushing et al., 2001; Perkins-Veazie and Collins, 2006;
Saftner et al., 2007).
The sensory quality of watermelon is mainly dependent
on sweetness and flesh crispness. The soluble solids con-
tent of watermelon is 85-90% sugars, and these sugars are
fructose, glucose, and sucrose (Table 28.1). The amount of
sucrose varies greatly among varieties and does not appear
until watermelon is about 50% ripe (Elmstrom and Davis,
1981). The ratios of fructose, glucose, and sucrose can be
1:1:1, 2:2:1, and 2:1:1, respectively (Elmstrom and Davis,
1981; Leskovar et al., 2004; USDA, 2010). The sugar con-
tent of watermelons will not increase after harvest, as the
plant provides all of the carbohydrate to the fruit. Over the
years, watermelons have become relatively high in soluble
solids content (SSC) a few days before full ripening. A
fruit at 10-12% SSC is highly desired, and this level can be
Table 28.1.
Composition of red-fleshed
watermelon.
Per
Serving
(280 g)
%DV
1
per
Serving
Per
100 g
Units
Water
g
91.45
256.06
∗
Total sugars
g
6.2
17.36
∗
Carbohydrate
g
7.55
21.14
7
Protein
g
0.61
1.71
3
Total lipid (fat)
g
0.15
0.42
1
Total dietary fiber
g
0.4
1.12
4
Vitamin C
mg
8.1
22.68
38
Vitamin A
IU
569
1593.2
32
Potassium
mg
112
313.6
9
Magnesium
mg
10
28
7
Copper
mg
0.042
0.12
6
Thiamin
mg
0.033
0.09
6
Pantothenic acid
mg
0.221
0.62
6
Vitamin B6
mg
0.045
0.13
6
1
Daily value, calculated as percentage of nutrient
recommended dietary intake based on a 2,000 calorie
daily diet.
Source: USDA (2010).
are triploid (3N), created by crossing 4N and 2N parents. It
is speculated that the flesh is firmer in these fruit because of
a higher number of fruit cells per unit area (Rushing et al.,
2001).
Peel (Epicarp)
Rind (mesocarp)
United lateral bundles
Heart
Inter locule
Locule (placental bundles)
Figure 28.1.
Photo of unripe watermelon showing tissues (dark areas around seeds indicate lycopene
formation).
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