Agriculture Reference
In-Depth Information
to be associated with varieties having high amounts of ly-
copene, such as 'Dixie Lee.' Unripe watermelons can ap-
pear pink (low in lycopene), while overripe watermelons
can be orange-red (more beta-carotene) (Perkins-Veazie
and Collins, 2006). Watermelons picked unripe then stored
too long develop a muted orange color but have a “green”
taste rather than the “squash” taste of an overripe fruit
(Saftner et al., 2007).
More details on the processing steps and food safety con-
siderations for fresh-cut melons are given later in this chap-
ter, under “Minimally Processed/Fresh-Cut Cantaloupe.”
Juice and juice concentrate
Production of watermelon juice is mainly for processing
into juice concentrate. Watermelon juice, on a limited scale,
is also prepared on site and on demand, rather than as a
heated or stored product. The flavor of the juice changes
quickly after processing, primarily from lipoxygenase ac-
tivity. Methods to stop lipoxygenase activity have been
marginally successful.
Juice extraction methods, (cold [22
◦
C] or hot macerate
[50
◦
C, 30 min] and heated and enzyme-treated macerate
[cellulose-pectinase enzyme added at 50
◦
C and held for
60 min]) can affect the content of lycopene, beta-carotene,
and total carotenoids in watermelon macerate (Fig. 28.2)
(Siddiq et al., 2005). The juice yield was also shown to im-
prove from cold macerate (82.50%) to 83.75% and 86.25%
from heated macerate and heated and enzyme treated mac-
erate, respectively. There was a significant decrease in the
amount of pomace (residue left) in heated and enzyme
treated macerate as compared to the other two methods
(Siddiq et al., 2005).
Watermelon concentrate is now being made and sold in
the United States and incorporated into juice blends (Milne
Fruit Products is one such company that has marketed
watermelon concentrate since around 2004). Concentrates
and juices may incorporate clarified or cloudy watermelon
juice. The watermelon juice powder is being made and dis-
tributed by one US company (Blue-California).
Processing and processed products
Minimally processed or fresh-cut products
The high pH and sugar content of fresh-cut watermelon
encourages microbial growth. Fresh-cut watermelon is pre-
pared and packaged in various ways. In Spain, water-
melons are cut transversely and sold as slices (Tarazona-
Diaz et al., 2011). In the United States, cubes are often
prepared and sold in polystyrene (plastic) containers, or
slices with rind are sold packaged in Styrofoam trays or
polystyrene containers. In Australia, most watermelons are
sold as cut fruit, rather than the large intact fruit found in
most stores in the United States (Gordon Rodgers, pers.
comm.).
Fresh-cut watermelon prepared as cubes can last up to
14 days at 5
◦
C (Perkins-Veazie and Collins, 2004; Fonseca
and Rushing, 2006). Drip loss, where cubes sit in juice that
has leaked from cubes, is an indicator of watermelon that is
close to the end of its shelf life, and the juice contains sug-
ars that can promote microbial growth. Factors that appear
to control this problem are the firmness of the watermelon
flesh and temperature management. Watermelons that are
slightly underripe or of firm fleshed seedless varieties have
less drip loss (Perkins-Veazie and Collins, 2004). Applica-
tion of chlorine dips, sprays, ozone, or hydrogen peroxide
sprays failed to extend shelf life of watermelon cubes, but
use of ultraviolet light-C (UV-C) up to 4.1 kJ/m
2
on pack-
aged watermelon reduced microbial load without adverse
quality changes (Fonseca and Rushing, 2006); higher UV-
C dozes were reported to induce higher CO
2
production
(Artes-Hernandez et al., 2010).
A number of studies have reported on the processing or
quality aspects of fresh-cut watermelons: precut sanitizer
treatment (McGlynn et al., 2003); calcium dips (Mao et al.,
2006); bioactive compounds and antioxidants (Perkins-
Veazie and Collins, 2004; Tarazona-Diaz et al., 2011);
volatile compounds (Beaulieu and Lea, 2006; Saftner et al.,
2007); respiration rate and shelf life (Fonseca et al., 2004);
and controlled atmosphere (CA) storage (Cartaxo et al.,
1999).
Juice blends
The very low acidity level of watermelon juice imparts
it a rather bland flavor, therefore, acidification with cit-
ric or ascorbic acid is necessary to attain an optimum
sugar-acid ratio and improve flavor significantly (Siddiq
et al., 2006). Since the juice blends (especially, using trop-
ical and subtropical fruit juices) market has seen a phe-
nomenal growth in recent years, the development of wa-
termelon juice blends with other fruit juices presents an
excellent opportunity for market expansion of lycopne-
rich, watermelon-based juices. Siddiq et al. (2006) investi-
gated the sensory quality of watermelon juice blends with
cherry, pineapple, mango, and white grape juice (Table
28.2). The watermelon-pineapple, watermelon-mango, and
watermelon-apple juice blends showed overall acceptabil-
ity scores of 6.15 to 7.25 on a 9-point hedonic scale.
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