Pomegranates

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Key Factswiki_pending

  • Due to high amounts of antioxidants, vitamins, potassium, folic acid and iron, pomegranates are frequently categorized as ‘superfoods’.
  • The Centers for Disease Control and Prevention (CDC) confirmed as of September 20, 2013 that approximately 162 people, primarily in the western U.S., became ill after consuming contaminated pomegranate arils.
  • The interior of the fruit is segmented by membranous walls into compartments packed with red, pink, or white flavorful pulp-filled sacs (arils). Ready-to-eat arils in plastic cups have become popular because of their convenience, unique taste, and health benefits.
  • Pomegranate roots and stems are not believed to be safe and should not be consumed, or should only be consumed in small doses.
  • The process of packaging pomegranate fruit into a ready-to-eat form can increase the amount of handling and the risk of contamination with foodborne illness pathogens.

Introduction

Fully matured pomegranates.
Fully matured pomegranates.

A shrub or small tree, standing 20 or 30 ft high, the pomegranate is well branched with thorns and exceptionally long-lived. Flowers on the branch tips can occur singly or in groups up to 5.  Almost rounded, but crowned at the base by the calyx, the pomegranate fruit is 2.5 to 5 inches in diameter and has a tough, leathery skin or rind. The fruit is yellow blanketed with light or deep pink or rich red coloring. The pomegranate is native to areas in the Middle East and across some parts of Asia. In the U.S, pomegranates are grown primarily in the dry zones of California and Arizona although the trees also grow in Utah, Texas, Louisiana, Alabama, Florida, and North Carolina.

Foodborne Outbreaks

Possibly due to the reported antimicrobial properties of pomegranates, there have not been many reported outbreaks. However, in 2013, pomegranate arils from Turkey were implicated in an outbreak of Hepatitis A virus. The Centers for Disease Control and Prevention (CDC) confirmed as of September 20, 2013 that approximately 162 people, primarily in the western U.S., became ill after consuming contaminated pomegranate arils. Three different brands of frozen ‘berries or kernels’ were associated with the outbreak. It was later determined that pomegranate arils which caused illnesses in Wisconsin and New Hampshire had been contaminated by fruit from California and Nevada, respectively.

Production

Pre-harvest

Pomegranates are primarily grown in mild-temperate to subtropical climates and grow in regions with cool winters and hot summers. Colder temperatures below 12º F (-11.11º C) can severely damage the pomegranate fruit. The trees are capable of tolerating drought and prefer a semi-arid climate. In southern Florida, fruit development is enhanced after a cold winter. The pomegranate prospers in soil that is calcareous and alkaline, in deep, acidic loam, and a wide range of soils in between these extremes. The pomegranate tree can grow in any soil that has good internal drainage. Pomegranates are susceptible to a number of insect infestations and plant diseases which can cause the loss of an entire crop or discoloration of fruits and arils unless properly managed.

Harvest and Post-Harvest

PomegranateTree
Pomegranates ripening on tree.

Pomegranate harvesting begins in August just before the fruit is fully mature. Pomegranates do not continue to ripen after harvest and should be picked when fully ripe for best eating quality. The fruit is ready for harvest if it makes a metallic sound when tapped.  Certain environmental conditions can cause pomegranate fruit to crack open including rain, wind, and insufficient irrigation. The stem is generally removed at harvest to prevent damage to other fruits during the shipping and handling process. In north and central Florida, pomegranate fruit ripen from July to October.

The fruit should be transported in cool temperatures and cushioned in wooden crates or in baskets, with paper or straw. Some growers use wax to cover the fruit to enhance the appearance. Improper humidity can lead to grey mold, which is caused by Botrytis cinerea fungus infection. Botrytis cinerea fungus can be prevented by using an approved fungicide or by keeping the pomegranates in a 15% carbon dioxide-enriched atmosphere. In California, an approved fungicide called Fludioxonil (Scholar) is used on pomegranates with a 5 ppm maximum residue limit. The pomegranates have to be dipped in the fungicide solution because the fungal spores are usually in the calyx area of the fruit, which may not be adequately covered by simply spraying. Subsequently, surface moisture must be removed by airflow to avoid having free moisture on the fruit in the transportation box.

 Although the fruits have a long storage life, pomegranates are prone to water loss and physical damage by abrasions, impacts, compression, and even vibrations.,

Maintaining the fruits at a temperature of 32 ºF to 41 ºF and sustaining a relative humidity of 80-85% can extend the storage life of a pomegranate fruit for up to 6-7 months while maintaining market quality.,, When the fruits are kept at room temperature, they continue to develop darker skin color and may last up to several weeks. Warmer temperatures and prolonged storage results in internal breakdown and increases dehydration, causing the fruit skin to harden and shrink. Shrink-wrapping is sometime used to preserve quality, surface color and reduces moisture loss. Chilling injury is a common occurrence due to improper storage. Chilling injury occurs when the fruit is exposed to temperatures below 41ºF during storage., The fruit will have a brown discoloration of the skin, pitting, and increased susceptibility to early decay., The arils will lose their rich red color and the white membranes will turn brown.,

Harvesting Arils

Pomegranate arils.
Pomegranate arils.

Two methods are typically used to collect the arils from the pomegranate: by hand and by commercial extraction. There are three commonly used techniques to collect the arils by hand:   (1) cut off the calyx end and lightly score the rind in quarters from top to bottom and then break the fruit open, peel the membrane back, and remove the arils;  (2)submerge the scored pomegranate in a bowl of cold water and soak for approximately 5 minutes. While holding the fruit under water, split the sections of the pomegranate and the arils will sink to the bottom; or (3) arils can also be removed by cutting the pomegranate in half, placing the cut face down while hitting the shell firmly with a blunt instrument. The section walls will break loose freeing the arils. To efficiently collect the arils by commercial extraction, a  6-step process is used. The benefits of commercial collecting via machine include increased efficiency and improved hygiene. Plastic containers with a thin, plastic film covering the arils are commonly used to commercially store the fruit. The arils are packed with air, nitrogen, and enriched oxygen to extend quality and shelf life. The commercial shelf life is estimated to be up to 18 days.

Food Safety

Some people have experienced allergies when consuming pomegranates or when rubbing the fruit on their skin or gums as a health supplement. Pomegranate roots and stems are not believed to be safe and should not be consumed, or should only be consumed in small doses.

Pomegranates may pass through many hands before selection by the consumer at the grocery store so consumers should be encouraged to wash the fruit well under running water before opening to remove the arils, this may also help in removing any pesticide residues. One method of removing the arils involves submerging and soaking scored pomegranates in a bowl of cold water for five minutes. Using this technique should begin with washing the whole fruit first to prevent cross contamination.

Consumption

To contribute to the Pomegranates Consumption section, please follow this link: http://fsi.colostate.edu/suggest-a-topic/

Nutrition

Pomegranates have a long history of being used to treat a variety of ailments and current scientific evidence does suggest this unique fruit provides health benefits. Over 120 different phytochemicals have been identified from pomegranate juice and antioxidant levels are reported to be higher than green tea or red wine. It has also been reported that consumption of pomegranate fruit or juice can reduce inflammation, combat heart disease, inhibit cancer and may slow the effects of aging., There are hundreds of arils in each pomegranate and each aril ‘sac’ houses a tiny seed called the embryo, which can be soft or hard. The tart flavor and refreshing sweetness of pomegranate is popular with consumers. An 8 oz. serving has 150 calories and is a good source of folate and potassium and a very good source of vitamin K. There has even been some limited evidence that theorizes that pomegranate fruit contains antiviral and antibacterial properties which protect against foodborne illnesses. More research is needed to confirm or deny this hypothesis.

 References

 

Authors

Nicole Breuner

Nicole Breuner

Corinna Gorgon

Corinna Gorgon

Kelsey Hanley

Kelsey Hanley

Marisa Bunning

Marisa Bunning