Agriculture Reference
In-Depth Information
Table 4.3 Most Important Citrus Importing Countries Reflecting Volumes and Types Traded.
Country
Tangerine
Other
Grapefruit
Lemons
Oranges
Total
Russian Federation
479 331
1804
11
203 911
490 955
1 176 012
Germany
353 960
3575
67 735
140 911
487 717
1 053 898
France
355 616
2448
96 921
120 572
427 573
1 003 130
Netherlands
186 403
1779
33
130 372
543 553
862 140
United Kingdom
283 604
952
19 797
94 506
344 180
743 039
United States
112 089
633
46
431 336
115 104
659 208
Saudi Arabia
36 135
10 355
1
64 065
310 086
420 642
Canada
121 331
1776
54 675
58 516
171 600
407 898
Poland
165 917
437
1550
97 011
109 583
374 498
Japan
4605
47
212 838
63 021
85 803
366 314
therefore do not ripen after harvest and should thus be
picked at the correct maturity stage. Citrus contains low
starch reserves and undergoes very slow internal quality
changes during storage (Davies & Albrigo 1994). Several
distinctive tissue types are visible when a fruit is cut
transversely; the most important are the segments con-
taining the juice vesicles and the outer rind or peel. The
peel is important since it protects the edible flesh and
regulates water loss during post-harvest storage. Grierson
(2006) provides a detailed morphological description of
citrus fruit.
Red') contain anthocyanin pigments (Chandler, 1958)
which cause the red colour in the flesh and rind.
The albedo is white in colour and consists of meris-
tematic cells. Initially, albedo tissue consists of tightly
packed cells, but as the fruit enlarges, the cells stretch to
form 'multi-armed' cells which connect with eight neigh-
bouring cells (Davies & Albrigo 1994). The resulting
tissue, a web of thin walled cells with large intercellular
spaces, is an extremely good cushion against pressure and
impact. The albedo in mature citrus can range from a few
millimetres to more than 10 mm depending on the cultivar
and growing conditions. However, the albedo is absent in
kumquats and little developed in mandarins (Tadeo et al .
2008).
External portion
In citrus, the external portion or rind of fruit consists pre-
dominately of two tissues, the exocarp or outer rind, called
the flavedo, and the inner mesocarp or albedo (Ladaniya
2008). The flavedo is the coloured portion of the rind, and
consists of the epicarp, hypodermis, outer mesocarp and oil
glands. The protective cuticle overlays the epicarp, with an
outer layer embedded with waxy material. The surface of
the epicarp is covered with lenticels, which function as the
main pathway for gas exchange (Burg 1990). Epidermal
cells in the flavedo tend to be polygonal in shape with no
intercellular spaces. The hypodermal cells are just below the
epicarp and surround the oil cells. The oil glands greatly
vary in size and may be sunken or bulge from the surface
contributing to the characteristic 'dimples' on the fruit rind.
Fruit contain β-carotene, xanthophylls (diol), cryptoxanthin
(monol) and violaxanthin (5,6-epoxide) as carotenoids,
which are responsible for the orange colour of the rind and
juice (Murata 1997). The carotenoid concentration may vary
depending on the concentration and composition among cit-
rus varieties as well as the growing conditions (Gross 1987).
Some varieties of citrus fruit such as blood orange ('Tarocco',
'Moro', Vascaro', 'Red Oval', 'Malta Blood Red' and 'Ruby
Internal portion
The edible portion of citrus is a spheroid shape consisting
of broadly triangular segments, each resembling a crescent
moon. A continuous membrane (endocarp) surrounds each
segment. Fruit pulp is green, orange, yellow or red, accord-
ing to the carotenoid and anthocyanin composition (Tadeo
et al . 2008). The interior of the segment contains many
small juice vesicles (pulp) and varying numbers of seeds.
Consumer preference is for fresh citrus with few seeds.
Some cultivars are commercially marketed as 'seedless',
but may still contain several seeds. Few cultivars are totally
seedless.
Nutritional value and chemical composition of fruit
The composition of citrus fruit varies with cultivar, climate
rootstock and cultural practices. Mature citrus pulp has a
very high percentage of water (85-90%) and many other
constituents which include carbohydrates, organic acids,
amino acids, folic acid, ascorbic acid (vitamin C), minerals
and small quantities of lipids, proteins, and secondary
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