Dates - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 174

DATE CONSUMPTION TRENDS
Date can be consumed at any of the three stages of its ma-
turity: Khalal, Rutab, and Ta m a r (Mortazavi et al., 2007).
The dates are a very marginal product in the consumer's
food basket, thus the typical supply-demand price dynam-
ics barely apply. In conventional date processing, dry or
soft dates are eaten as whole fruit, seeded and stuffed, or
chopped and used in a great variety of ways: as ingredients
in cereals, puddings, breads, cakes, cookies, ice cream, and
confectionaries. Surplus dates are processed into cubes,
paste, spread, powder (date sugar), jam, jelly, juice, syrup,
vinegar, or alcohol. Decolored and filtered date juice yields
a clear invert sugar solution (Morton, 1987).

stage sprayed with ethanol, sealed in thick plastic bags for
24 hours, then incubated at 22 ◦ Cfor6days(Faragand
AI-Konaissi, 2001). Such study provides evidence about
the role of ethanol fumes in removing astringency and in-
ducing Rutab development in 'Helali' dates. Successful ap-
plications of Ethrel were either obtained with non-stringent
cultivars at the Khalal stage (El-Hamady et al., 1983) or
were accompanied with fruit thinning (El-Hamady et al.,
1992). There were no significant differences in Rutab yield
per bunch between sprays or injection of Ethrel into the
bunch peduncle.
Postharvest dipping of fruit at the Bisir stage in Ethrel
at 4.2 ml/l and abscisic acid at 1.0 mM significantly en-
hanced ripening. Neither treatment showed any negative
impact on the overall quality characteristics of ripe fruit,
suggesting that they may be practical tools for increasing
the ripening rate of 'Helali' dates at Bisir stage (Awad,
2007). It has been reported that ethephon application at
500 ppm, 1000 ppm, or 1500 ppm shortly after full bloom
on 'Zaghloul' and 'Samani' date palms grown in Egypt
advanced fruit ripening by about 1 month, especially at
the concentration of 1500 ppm (Kamal, 1995). Accord-
ingly, Musa (2001) reported that the effectiveness of Ethrel
in enhancing fruit ripening of 'Mishrigi Wad Khatib' and
'Mishrigi Wad Lagi' dates grown in Khartoum, Sudan,
was two- to threefold higher by injecting 2 ml of Ethrel
(480 g/l) into a pit made in the peduncle compared with
1,000 ppm of Ethrel spraying over the fruit. However,
especially in hot arid regions, the effectiveness of ethep-
hon sprays was very low, more variable, and gave unpre-
dictable results even when applied at a high concentration
(1000 ppm) (El-Hamady et al., 1993; Al-Juburi et al., 2001).

POSTHARVEST PHYSIOLOGY
The postharvest losses in date palm fruits can be minimized
to a great extent by harvesting dates at the right stage and
storing fruit under appropriate storage conditions. A dis-
cussion of the postharvest processes that affect date quality
follows.

Role of ethylene in date ripening
Ethylene plays a key role in the initiation of ripening in cli-
macteric fruits, although the mechanism by which ethylene
carries out its action has not been fully understood (Ecker,
1995). Abdel-Latif (1988) reported that the ethylene pro-
duction rate was very high in 'Zahdi,' 'Derey,' and 'Sultani'
date cultivars during early stages of fruit development and
decreased as the fruit advanced in maturity but rose again
to a high level at the fruit-ripening phase. Similarly, Ser-
rano et al. (2001) reported that in early ripening stages of
dates, a small peak in ethylene production was detected,
followed by a peak in respiration rate, suggesting that dates
are climacteric fruit.
When date fruit ripens, the rate of respiration increases
2.5-fold, whereas the rate of ethylene production increases
360-fold. The rate of ethylene production by ripe date fruit
is considered moderate (Kader and Kasmire, 1984). Espla
et al. (1999) found that the amount of ethylene produced
varied from 10 − l

Enzyme activity
Prolonged storage of dates under refrigeration or freez-
ing is based mainly on the slowing down of enzyme ac-
tivity. Enzymes such as phytase, invertase and peroxidase
(POD), and polyphenoloxidase (PPO) have been isolated
in dates (Nadkarni, 1976). The PPO activity of 'Deglet
Nour' date extracts decreased after heat treatment in the
25 ◦ -70 ◦ C range (Belarbi et al., 2001c). Enzyme activity
normally takes place in solution or atmosphere. Date fruit
POD and PPO activities increase after 4 days at 21 ◦ C,
14 days at 5 ◦ C, and are slightly affected after 90 days at
−

10 − l kg/hr, according to the
palm tree group growing in Elche (Spain), suggesting dif-
ferential ethylene production as one of the causes leading
to fruit ripening.

to 20-30 ×

18 ◦ C (Alkhalifa and Dilshad, 1998).

Artificial ripening
Induction of Rutab development in some dates varieties
such as 'Helali' dates is a major concern for date producers
that can result in unmarketable fruit. Ethanol fumes alone at
50% could be used after harvest to fully induce Rutab devel-
opment (ripening) in 'Helali' date fruits at the full Khalal

Water activity and water sorption isotherms
Dates are hydroscopic and lose or gain moisture until
equilibrium is reached with the relative humidity of the
surrounding air. This relationship is expressed in terms of
equilibrium moisture content (EMC) or in terms of ERH