By Malinda Geisler, content specialist, AgMRC, Iowa State University, malindag@iastate.edu.

Profile revised November 2007.


Overview
Pomegranate is a colorful fruit that is gaining attention from food manufacturers. According to Productscan Online, 190 new pomegranate-flavored foods and beverages were introduced in the United States in 2005, up from 31 products in 2003. The rich color, sweet-sour flavor and high antioxidant content are reasons why manufacturers are adding pomegranate to such products as jelly, ice cream bars, truffles and chewing gum.

There is no worldwide information about pomegranate production or sales. The United States Department of Agriculture stopped collecting pomegranate data in 1989. According to the Pomegranate Council, however, about 250 growers in the San Joaquin Valley of California produce 80 percent of the U.S. pomegranate crop on approximately 14,000 acres.

Steeped in history and romance and almost in a class by itself, the pomegranate, Punica granatum L., belongs to the family Punicaceae, which includes only one genus and two species. The other one, little-known, is P. protopunica Balf., peculiar to the island of Socotra.

An attractive shrub or small tree, to 20 or 30 feet high, the pomegranate is much-branched, more or less spiny and extremely long-lived. Some specimens at Versailles are known to have survived two centuries. It has a strong tendency to sucker from the base.

Nearly round, but crowned at the base by the prominent calyx, the fruit, 2 1/2 to 5 inches wide, has a tough, leathery skin or rind, basically yellow more or less overlaid with light or deep pink or rich red. The interior is separated by membranous walls and white spongy tissue (rag) into compartments packed with transparent sacs filled with tart, flavorful, fleshy, juicy, red, pink or whitish pulp (technically the aril). In each sac, there is one white or red, angular, soft or hard seed. The seeds represent about 52 percent of the weight of the whole fruit.

The pomegranate tree is native from Iran to the Himalayas in northern India and has been cultivated since ancient times throughout the Mediterranean region of Asia, Africa and Europe. The fruit was used in many ways as it is today. 

In Mexico it is frequently planted, and it is sometimes found in gardens in Hawaii. The tree was introduced to California by Spanish settlers in 1769. It is grown for its fruit mostly in the dry zones of that state and Arizona. In California, commercial pomegranate cultivation is concentrated in Tulare, Fresno and Kern counties, with small plantings in Imperial and Riverside counties. There were 2,000 acres of bearing trees in these areas in the 1920s. Production declined from lack of demand in the 1930s, but new plantings were made when demand increased in the 1960s.

The species is primarily mild-temperate to subtropical and naturally adapted to regions with cool winters and hot summers, but certain types are grown in home dooryards in tropical areas, such as various islands of the Bahamas and West Indies. In Southern Florida, fruit development is enhanced after a cold winter. Elsewhere in the United States, the pomegranate can be grown outdoors as far north as Washington County, Utah, and Washington, D.C., though it does not fruit in the latter locations. It can be severely injured by temperatures below 12 degrees F. The plant favors a semi-arid climate and is extremely drought-tolerant.

The pomegranate thrives on calcareous, alkaline soil and on deep, acidic loam and a wide range of soils in between these extremes. The pomegranate is both self-pollinated and cross-pollinated by insects. There is very little wind dispersal of pollen.

Pomegranate seeds germinate readily. Even when merely thrown onto the surface of loose soil, the seedlings spring up with vigor. However, to avoid seedling variation, selected cultivars are usually reproduced by means of hardwood cuttings 10 to 20 inches long. Treatment with 50 ppm. indole-butyric acid and planting at a moisture level of 15.95 percent greatly enhances root development and survival. The cuttings are set in beds with one or two buds above the soil for one year and then transplanted to the field. Grafting has never been successful, but branches may be air-layered and suckers from a parent plant can be taken up and transplanted.

Rooted cuttings or seedlings are set out in pre-fertilized pits 2 feet deep and wide and are spaced 12 to 18 feet apart, depending on the fertility of the soil. Initially, the plants are cut back to 24 to 30 inches in height, and after they branch out, the lower branches are pruned to provide a clear main stem. Because fruits are borne only at the tips of new growth, it is recommended that, for the first three years, the branches be judiciously shortened annually to encourage the maximum number of new shoots on all sides, prevent straggly development and achieve a strong, well-framed plant. After the third year, only suckers and dead branches are removed. For good fruit production, the plant must be irrigated. In California, irrigation water is supplied by overhead sprinklers, which also provide frost protection during cold spells. The pomegranate may begin to bear in one year after planting, but two and a half to three years is more common.

The fruits ripen six to seven months after flowering. In California, maturity has been equated with 1.8 percent titratable acidity (TA) and SSC of 17 percent or more. The fruit cannot be ripened off the tree even with ethylene treatment. Growers generally consider the fruit ready for harvest if it makes a metallic sound when tapped. The fruit must be picked before over maturity when it tends to crack open if rained upon or under certain conditions of atmospheric humidity, dehydration by winds or insufficient irrigation. Of course, one might assume that ultimate splitting is the natural means of seed release and dispersal.

The fruits should not be pulled off but clipped close to the base, leaving no stem to cause damage in handling and shipping. Appearance is important, especially in the United States where pomegranates may be purchased primarily to enhance table arrangements and other fall (harvest-time) decorations. Too much sun exposure causes sunscald–brown, russeted blemishes and roughening of the rind. The fruit ships well, cushioned with paper or straw, in wooden crates or, for nearby markets, in baskets. Commercial California growers grade the fruits into eight sizes; pack in layers, unwrapped but topped with shredded plastic, in covered wood boxes; precool rapidly; and ship in refrigerated trucks.

The pomegranate is equal to the apple in having a long storage life. It is best maintained at a temperature of 32 degrees to 41 degrees F. The fruits improve in storage, become juicier and more flavorful; may be kept for a period of 7 months within this temperature range and at 80 to 85 percent relative humidity, without shrinking or spoiling. At 95 percent relative humidity, the fruit can be kept only two months at 41 degrees F, but for longer periods at 50 degrees F. After prolonged storage, internal breakdown is evidenced by faded, streaky pulp of flat flavor.

According to the Pomegranate Council, fresh pomegranates are available from September through January. Concentrate is available throughout the year.

In South Carolina, people make pomegranate jelly by adding 7 1/2 cups of sugar and 1 bottle of liquid pectin for every 4 cups of juice. Pomegranate juice is widely made into grenadine for use in mixed drinks. In the Asiatic countries, it may be made into a thick syrup for use as a sauce. It is also often converted into wine. In the home kitchen, the juice can be easily extracted by reaming the halved fruits on an ordinary orange juice squeezer.

All parts of the tree have been utilized as sources of tannin for curing leather. The trunk bark contains 10 to 25 percent tannin and was formerly important in the production of Morocco leather. The root bark has a 28 percent tannin content, the leaves, 11 percent, and the fruit rind as much as 26 percent. The latter is a by-product of the "anardana" industry. Both the rind and the flowers yield dyes for textiles. Ink can be made by steeping the leaves in vinegar. In Japan, an insecticide is derived from the bark. The pale-yellow wood is very hard and, while available only in small dimensions, is used for walking sticks and in woodcrafts.

Pomegranate juice was found to have high levels of antioxidants. Research indicates consumption of pomegranate juice may help prevent hardening of the arteries.

http://www.foodproductdesign.com/articles/631news.html

Pomegranate Juice May Clear Clogged Arteries, WebMD.com, 2005. 

http://www.webmd.com/content/article/102/106690.htm

Pomegranate, In: Fruits of Warm Climates, Purdue University, 1987. 

http://www.hort.purdue.edu/newcrop/morton/pomegranate.html

Pomegranate Council

http://www.pomegranates.org/techinfo.html