Pomegranate
M. Pekmezci and M. Erkan
ekmezci and Erkan are with the Department of Horticulture, Faculty of Agriculture, Akdeniz
University, Turkey.
Scientific Name and Introduction
Punica granatum L., the pomegranate, belongs to the Punicacea family and is one of the oldest
known edible fruits. It is sometimes called Chinese apple and has been cultivated extensively in
Mediterranean countries (Tunisia, Turkey, Israel, Egypt, Spain, and Morocco), Iran, Afghanistan,
India, and to some extent in the United States (California), China, Japan, and Russia. The
pomegranate requires a long, hot summer for fruit to mature, but it can withstand low
temperatures in winter and is drought- and salt-tolerant.
Pomegranate fruit is nearly round with a prominent attached calyx and a hard, leathery skin.
Surface color varies among commercial cultivars from yellow with a crimson cheek to solid
brownish-red and also bright-red. The edible portion is the bright-red pulp (aril) surrounding the
individual seed. The fruit is consumed fresh, or it can be processed into juice, syrup, jams, or
wine. Fruit of the wild-type pomegranate is acidic, but cultivated cultivars bear fruit with a
sweet-sour or sweet flavor. There are several types of edible pomegranate, and there are
ornamental types with double flowers, largely sterile, which are not grown for edible fruit.
Several cultivars are grown commercially around the world, including ‘Wonderful’ in California
and Israel, ‘Mollar’ and ‘Tendral’ in Spain, ‘Schahvar’ and ‘Robab’ in Iran, ‘Hicaznar’ and
‘Beynar’ in Turkey, and ‘Zehri’ and ‘Gabsi’ in Tunisia (LaRue 1980, Onur and Kaşka 1985,
Morton 1987, Patil and Karale 1990, Llacer et al. 1994, Mars 1994).
Quality Characteristics and Criteria
Fruit quality depends largely on sugar and acid content of the juice. A high-quality pomegranate
should also have an attractive skin and small seeds in the aril and should be free from sunburn,
growth cracks, cuts, bruises, and decay. Skin color and smoothness are also quality indices. Sour
and sour-sweet pomegranates have reddish skin, in contrast to sweet pomegranates which have
yellowish-green skin. Skin thickness varies from 1.5 to 4.24 mm (Küpper 1995). Skin contains
30% tannin, which is used in medical and dye industries.
Pomegranates are low in vitamin C, an important nutritional quality component, compared to
many other fruits. Vitamin C content ranges from 0.49 to 30 mg per 100 g juice depending on
cultivar (Hussein and Hussein 1972, Küpper 1995). Juice content of pomegranates is 45 to 65%
of the whole fruit or 76 to 85% of the aril.
Horticultural Maturity Indices
Pomegranates can be harvested when they reach a certain size and skin color. Other maturity
indices are TA and SSC. Each pomegranate type requires a certain TA:SSC at harvest. TA of
pomegranates varies between 0.13 and 4.98% at harvest (Küpper 1995). The TA is 1% in sweet
cultivars, 1 to 2% in sweet-sour cultivars, and >2% in sour cultivars (Onur and Ka?ka 1985).
SSC of pomegranates varies from 8.3 to 20.5% at harvest (Küpper 1995). Thus, maturity indices
depend on cultivar. For example, TA 1.85% and SSC ≥17% are recommended for Californiagrown
‘Wonderful’ fruit (Ben-Arie et al. 1984, Elyatem and Kader 1984). Juice tannin content
0.25% is preferred, and red juice color equal to or darker than Munsell color chart 5R 5/12 is
desirable (Crisosto et al. 1996).
Grades, Sizes, and Packaging
There are no U.S. grades. Only a small number of pomegranates have been grown historically in
the U.S., mostly in California and Arizona. Therefore, most fruit are imported for the U.S.
market. Pomegranates are classified into four groups based on size. Under Turkish standards,
sizes are defined as—
Small |
150 to 200 g |
65 to 74 mm diameter |
25 to 34 fruit per 5-kg carton |
Medium |
201 to 300 g |
75 to 84 mm diameter |
17 to 25 fruit per 5-kg carton |
Large |
301 to 400 g |
85 to 94 mm diameter |
13 to 17 fruit per 5-kg carton |
Extra Large |
401 to 500 g |
94 to 104 mm diameter |
10 to 13 fruit per 5-kg carton |
Fruit are generally packed into 2-layer tray packs or bulk cartons
Optimum Storage Conditions
Optimum storage temperature varies by cultivar, production area, and postharvest treatment
(Mercantilia 1989, Hardenburg et al. 1990, Köksal 1989, Snowdon 1990, SeaLand 1991, Onur et
al. 1995). The recommended conditions for storage of ‘Hicaznar’ are 6 °C (43 °F) with 90% RH
(Onur et al. 1992, 1995, Pekmezci et al. 1998). Storage of ‘Wonderful’ at < 5 °C (41 °F) resulted
in chilling injury, and severity of symptoms increased with time and temperature below 5 °C
(Elyatem and Kader 1984). Control of RH is critical in storage because skin desiccates readily at
low RH, resulting in hard, darkened rinds, which are unattractive and reduce marketability. RH
of 90 to 98% is preferred for storage (Salunkhe and Desai 1984). Waxing fruit and storage in
plastic liners can reduce weight loss (Küpper 1995).
Controlled Atmosphere (CA) Considerations
CA storage has the advantage of reducing loss of TA and vitamin C (Küpper et al. 1995).
Optimal CA levels for pomegranate storage are 3% O2 and 6% CO2 (Küpper et al. 1995).
‘Hicaznar’ fruit can be stored for 6 mo at 6 °C (43 °F) under CA (Pekmezci et al. 1998).
Retail Outlet Display Considerations
Pomegranates should not be water-sprinkled or top-iced.
Chilling Sensitivity
Pomegranates are susceptible to chilling injury and should not be stored at < 5 °C (41 °F).
External symptoms include rind pitting, brown discoloration of the skin, and increased
susceptibility to decay. Internal symptoms include a pale aril color and brown discoloration of
the white segments separating the arils (Elyatem and Kader 1984).
Ethylene Production and Sensitivity
Pomegranates produce very low amounts of ethylene: < 0.1 μL kg-1 h-1 at up to 10 °C (50 °F) and
< 0.2 μL kg-1 h-1 from 10 to 20 °C (50 to 68 °F) (Elyatem and Kader 1984). Fruit are not
particularly sensitive to ethylene exposure, though ethylene at ≥1 μL L-1 stimulates respiration
and autocatalytic ethylene. Ben-Arie et al. (1984) reported that ethylene treatment of
‘Wonderful’ pomegranates caused a rapid but transient rise in CO2 but no change in SSC, TA, or
fruit and juice color. Pomegranates do not ripen after harvest and must be picked fully ripe.
Respiration Rates
Pomegranate is a nonclimacteric fruit and has a very low respiration rate that declines with time
in storage.
Temperature |
mg CO2 kg-1 h-1
|
5 °C |
4 to 8 |
10 °C |
8 to 16 |
20 °C |
16 to 36 |
Data from Crisisto et al. (1996). |
To get mL CO2 kg-1 h-1
, divide the mg kg-1 h-1 rate by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F),
and 1.8 at 20 °C (68 °F). To calculate heat production, multiply mg kg-1 h-1 by 220 to get BTU
ton-1 day-1 or by 61 to get kcal tonne-1 day-1
.
Physiological Disorders
Chilling injury (CI) is the most common physiological disorder during storage. Incidence and
severity of CI depend on temperature and duration. Symptoms are especially apparent upon
removal of fruit from cold storage to 20 °C (68 °F). External CI symptoms include surface
pitting, skin discoloration, scald, and dead skin tissues. Internal symptoms include dead tissues,
brown discoloration of the white segments separating the arils, and pale aril color (Elyatem and
Kader 1984). Husk scald (brown superficial discoloration) is another manifestation of CI in
pomegranate; it is a restricted to the husk. At advanced stages, scalded areas became moldy.
Scald symptoms become evident after 8 weeks of storage at 2 °C (36 °F).
Splitting and cracking occur in fruit on the tree. The rind shows various degrees of cracking,
which often serves as entry points for decay organisms (Salunkhe and Desai 1984). Splitting and
cracking can be prevented by using regular irrigation; the last irrigation must be done 15 to 20
days before harvest
Internal breakdown is another physiological disorder in pomegranate fruit. The pulp-bearing
seeds (arils) do not develop their typical red color and are somewhat flattened rather than plump
(Ryall and Pentzer 1974).
Postharvest Pathology
Gray mold rot (Botrytis cinerea), green mold rot (Penicillium digitatum), and Cladosporium spp.
are the main postharvest diseases of pomegranate fruit. Gray mold usually starts at the calyx. As
it progresses, the skin becomes light-brown, tough, and leathery. Heart rot is another disorder; it
may be caused by Aspergillus spp. and Alternaria spp. Affected fruit show slightly abnormal
skin color and a mass of blackened arils; disease develops while fruit are on the tree (Salunkhe
and Desai 1984).
Quarantine Issues
There are no known quarantine issues.
Suitability as a Fresh-Cut Product
Possibly, but none are fresh-cut at this time.
Special Considerations
Pomegranates do not ripen after harvest and must be picked fully ripe to ensure the best eating
quality.
References
Ben-Arie, R., N. Segal, and S. Guelfat-Reich. 1984. The maturation and ripening of the
‘Wonderful’ pomegranate. J. Amer. Soc. Hort. Sci. 109:898-902.
Crisosto, C.H., E.J. Mitcham, and A.A. Kader. 1996. Pomegranates. Perishables Handling
Quarterly 85:17-18. At http://postharvest.ucdavis.edu/pffruits/pomegranate.
Elyatem, M.S., and A.A. Kader. 1984. Postharvest physiology and storage behavior of
pomegranate fruit. Sci. Hort. 24:287-298.
Hardenburg, R.E., A.E. Watada, and C.Y. Wang. 1990. The Commercial Storage of Fruits,
Vegetables, and Florist and Nursery Stocks, rev. Agricultural Handbook 66, U.S. Department of
Agriculture, Washington, DC.
Hussein, M.A.H., and M.A.S. Hussein. 1972. Suitability of pomegranate varieties for processing.
Assuit J. Ag. Sci. 3:303-307.
Köksal, I. 1989. Research on the storage of pomegranate cv. ‘Gökbahçe’ under different
conditions. Acta Hort. 258:295-302.
Küpper, W. 1995. Wirkungen von Temperatur und CO2-Konzentration in der Langfristigen CALagerung
auf Verschiedene Qualitaetsmerkmale und die Respiration Waehrend der
Nachlagerungsphase des Granatapfels (Punica Granatum L.) der Sorte ‘Hicaznar.’ Ph.D. thesis,
Institut für Obstbau und Gemüsebau der Rheinschen, Friedrich-Wilhelms-Univertat., Bonn,
Germany.
Küpper, W., M. Pekmezci, and J. Henze. 1995. Studies on CA-storage of pomegranate (Punica
granatum L., cv. ‘Hicaz’). Acta Hort. 398:101-108.
LaRue, J.H. 1980. Growing pomegranates in California. Leaflet 2459, University of California,
Division of Agricultural Science, Davis, CA.
Llacer, G., R. Martinez Valero, P. Melgarejo, et al. 1994. Present status and future prospects of
underutilized fruit tree crops in Spain. pp. 63-75. In First Meeting CIHEAM Coop. Res. Network
Underutilized Fruit Trees, 1994, Zaragoza, Spain.
Mars, M. 1994. La culture du granadier (Punica granatum L.) et du figuier (Ficus carica L.) en
tunisie. pp. 76-83. In First Meeting CIHEAM Coop. Res. Network Underutilized Fruit Trees,
1994, Zaragoza, Spain.
Mercantila. 1989. Guide to Food Transport. Fruit and Vegetables. Mercantilia, Copenhagen,
Denmark.
Morton, J. F. 1987. Fruits of Warm Climates. Julia F. Morton, Miami, FL.
Onur, C. 1989. Nar muhafazas?nda bir yenilik [News on pomegranate storage]. Derim 6:88-93.
Onur, C., and N. Kaska. 1985. Akdeniz bölgesi narlar?n?n (Punica granatum L.) seleksiyonu
[Selection of pomegranate of Mediterranean region]. Turkish J. Agric. For., D2, 9, 1:25-33.
Onur, C., M. Pekmezci, H. Tibet, et al. 1992. Hicaznar?n?n so?ukta muhafazas? üzerinde bir
ara?t?rma [Research on cold storage of pomegranate cv. Hicaznar]. In Proceedings of Turkey 1st
National Horticulture Congress, October 13-16, 1992, Ege University Agricultural Faculty, pp:
209-212.
Onur, C., M. Pekmezci, H. Tibet, et al. 1995. Nar (Punica granatum L.) muhafazas? üzerinde
ara?t?rmalar [Investigations on pomegranate storage]. In Proceedings of 2nd National
Horticulture Congreess, 3-6 October, 1995, Adana, Turkey, vol 1, pp. 696-700. çukurova
University,
Patil, A.V., and A.R. Karale. 1990. Pomegranate. In T.K. Kose and S.K. Mitra, eds., Fruits:
Tropical and Subtropical, pp. 614-631. Naya Prokash, Calcutta, India.
Pekmezci, M., M. Erkan, H. Gübbük, and S. Gözlekçi. 1998. Effect of modified atmosphere on
storage of pomegranate fruits (cv. Hicaznar). 25th International Horticultural Congress, Brussels,
Belgium. Acta Hort. PP2/04/A10:368
Ryall, A.L., and W.T. Pentzer. 1974. Handling, Transportation and Storage of Fruit and
Vegetables, vol. 2. AVI, Westport, CT.
Salunkhe, D.K., and B.B. Desai. 1984. Postharvest Biotechnology of Fruits, vol. 2. CRC Press,
Boca Raton FL.
SeaLand Service. 1991. Shipping guide to perishables. SeaLand Service, Iselim, NJ.
Snowdon, A.L. 1990. A Colour Atlas of Postharvest Diseases and Disorders of Fruits and
Vegetables, vol. 1, General Introduction and Fruits. Wolfe Scientific, London, U.K.
Additional Reading
Artes, F., J.G. Marin, and J.A. Martinez. 1996. Controlled atmosphere storage of pomegranate.
Z. Lebensm. Unters. Forsch. 203:33-37.
Ben-Arie, R., and E. Or. 1986. The development and control of husk scald on ‘Wonderful’
pomegranate fruit during storage. J. Amer. Soc. Hort. Sci. 111:395-399.
Gil, M., F. Artes, and F. Tomas-Barberan. 1996. Minimal processing and modified atmosphere
packaging effects on pigmentation of pomegranate seeds. J. Food Sci. 61:161-164.
Gil, M.I., R. Sanchez, J.G. Marin, and F. Artes. 1996. Quality changes in pomegranates during
ripening and cold storage. Z. Lebensm. Unters. Forsch. 202:481-485.
Kader, A.A., A. Chordas,, and S. Elyatem. 1984. Responses of pomegranates to ethylene
treatment and storage temperature. Calif. Agri. 38(748):14-15.
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