Introduction
Globally, plums are one of the most popular stone fruits in today’s world. Nations such as the United States of America, China, and Romania are a few of the leading producers of this fruit and it is well known for its health benefits as well as its commercial success. There are over 2000 species of plums and they are usually eaten fresh.
To ensure an all-year-round preservation, plums are sometimes dried, canned or made into a beverage. Dehydration to a desired moisture content is a preferred preservation method than sun drying especially due to the high sugar content of plums. Additionally, controlled dehydration (especially using sub-atmospheric conditions) helps retain the sensory integrity and nutritional quality of the fruits.
Drying techniques available include osmotic dehydration, hot air drying, vacuum drying, and microwave drying. Drying is an essential process for fruit preservation. It helps significantly reduce the moisture content of the fruits and thereby creates an unfavourable environment for microbial survival and/or growth.
This hinders the invasion of spoilage organisms and ensures the fruit retains its nutritional and sensory quality for a longer period and can withstand the rigours of transportation and climate variations.1
Plums: types and historical background
Plums are known to have different varieties and therefore, have quite a widespread origin all over the world. Records show that since pre-historic times, plum cultivation has been in existence. European plums are believed to be more than 2,000 years old while records that date as far back as 470 B.C. provide data on plums. Similarly, ancient Romans were known to consume European plums with a record of about 300 types of plums!
Plums that are referred to as Japanese plums today are known to have originally originated in China about 200 to 400 years ago before it was further introduced to the rest of the World. Fortunately, plums have adapted to different climates over the decades and can be cultivated across the globe. Hence, there are different varieties of the fruit. These include
- the European plum (Prunusdomestica)
- the Damson plum of West Asia (Prunussalicina)
- the American plum (Prunus Americana)
- and the Cherry plum of South Asia (Prunuscerasifera)1
Poland is also popular for its commercial trade of plums. Here, plum trees rank the 3rd highest (6.7 %) after apple and cherry trees, 71.4 and 13.5 % respectively. These fruits are cultivated as cash crops in commercial orchards, gardens and allotments. They are consumed fresh, frozen, dried or processed (such as into plum jam).2
Plums: characteristics and chemical composition
There are a broad variety of plums and they are in many colours and sizes. Colours range from red, green, and yellow to white. They have a high concentration of bioactive components. Some of these include pectins, carotenoids, phenolic acids, and anthocyanins. They are popular in Indian herbal medicines in the treatment of irregular menstruation and even miscarriages.1
The existence of various species of plum equals the variations in the concentrations of their compositions. Plums generally contain a high concentration of carbohydrates (as much as 15 g/ 100 g) which make up a significant dietary requirement of available energy. It also contains a high content of fiber, sorbitol and fructose which helps ensure improved glycemic control.
The high content of pectin which is up to 1 % fresh weight also makes it of high nutritional value. The mineral potassium is very predominant (up to 200 mg/ 100 g) as well as β-carotene (up to 780 μg/100 g). They are a prominent source of antioxidants that help remove harmful free radicals and oxidants which are results of metabolic breakdowns and pollutants from human bodies, protecting against genetic mutations and diseases. Some examples of antioxidant compositions include phenolic acids and flavonoids among others.2
Health benefits of plum
The dried forms of plum or their juice extracts are advantageous in the treatment of constipation due to their high fibre content. This fibre composition also provides the benefits of glucose tolerance and the metabolism of lipids. The chlorogenic acid content of dried plum may be associated with glucose metabolism benefits and also provide immune enhancement benefits, particularly against some cancer tumour cells.
As earlier stated, this fruit also provides antioxidant properties which play a huge role in cardiovascular disease prevention, and bone loss such as osteoporosis which is very beneficial for post-menopausal women. There is an emerging body of evidence that affirms that dried plums exert benefits on bones and that daily consumption has been shown to slow down bone cell turnover and overall increase bone mineral density and confer bone-protective properties on post-menopausal women. Studies have also shown that dried plums have cholesterol-lowering benefits in human and animal consumption.3,5
Plums are generally considered a popular healthy food in the West. They are used along with other medicinal plants in India in the treatment of Leukorrhoea. The phenolic component not only contributes to the colour of many vegetables and fruits but is also essential in the health-benefit functionality of these foods.
They protect humans from diseases that are associated with advancement in age through the prevention of low-density lipoprotein (LDL) from oxidation. Dried plums are a great source of vitamin K and potassium.4 Plums ingested in their dried forms or extracts are a means to meet daily dietary requirements for food consumption. They enhance the formation of bone through cell signaling which is essential in osteoblast and osteoclast differentiation.5
Dried plums have been shown to elicit anti-microbial effects on food spoilage microbes as well as in the urinary tract and gastrointestinal tract. This is due to their distinct components such as sorbitol. Sorbitol also finds use in the control of dental decay because of its low cariogenicity in comparison with glucose or sucrose present in many other dried fruits.
The mechanism of action of sorbitol here is attributed to the fact that bacteria causing dental plaque do not break down sugar alcohols, therefore, cariogenic flora is suppressed when dried plum is chewed. The phenolic components can also provide antimicrobial activity in the mouth. The high content of fibre and sorbitol in dried plum may also help in the prevention of certain cancers such as colon cancer.
This has been attributed to their ability to decrease the transit time of faecal matter in the colon and the dilution of faecal bile acids increasing their weight. This is outside the beneficial effect of phenolic components which help prevent DNA damage in the epithelium of the colon. Plums (both fresh and dried) have been shown to have the ability to bind bile acids better especially in their powder forms.
Dried plums contain sorbitol and therefore have low GI (Glycemic Index) of 9. Low GI foods are known to be more satiating than their high GI counterparts and are desirable in the management of diabetes as well as weight control because they do not cause a significant rise or fall in blood glucose levels. Generally, daily dried fruit consumption (1 oz/day) has been shown to lead to reduced abdominal obesity.6
Summary
Plums are globally recognized as one of the most popular stone fruits and they are celebrated for their countless health benefits. Plums are made up of over 2000 species with different shapes, colours and sizes, some of these are:
- The European plum (Prunusdomestica)
- The Damson plum of West Asia (Prunussalicina)
- The American plum (Prunus Americana)
- The Cherry plum of South Asia (Prunuscerasifera)
They can be consumed fresh, frozen, dried or processed into a delicious jam or other beverage product.
Plums date back to prehistoric times and it boasts of historical use across Europe, Asia and America, ranking third after apple and cherry as cash crops!
Plums have been used for centuries in Indian cultures in the treatment of irregular menstruations and adjunct treatments in miscarriages. It is also globally known for its antioxidant benefits due to its ability to mop up free radicals and harmful oxidants in the human body. Dried plums are also used in the treatment of constipation because of their high content of fibre.
Additionally, this fibre component has been found to contribute to improved glucose-blood level control and lipid metabolism. Dried plums also contribute to immunity against some cancer tumour cells and research shows that daily consumption of at least two servings slows down bone cell turnover which is a beneficial characteristic among post-menopausal women that may be pre-disposed to loss of bone density.
Moreover, dried plums provide some antimicrobial properties which prevent spoilage and help retain the nutritional benefit of the fruit for longer periods as well as protect invasion of pathogenic microorganisms in the urinary tract system and gastrointestinal systems.
Conclusion
Plums have a rich history and different varieties. They provide a high amount of dietary support and they are a powerhouse of health benefits. They aid digestion and glycemic control, support bone health and provide antimicrobial protection within and outside the body. As research continues to reveal more benefits, plums are likely to gain more scientific and medical attention globally, securing their place as a delicious and nutritious fruit with countless beneficial characteristics.
References
- Birwal, Preeti, et al. ‘Plums: A Brief Introduction’. Journal of Food, Nutrition and Population Health, vol. 1, no. 1, 2017, pp. 1–5.
- Walkowiak-Tomczak, Dorata. ‘CHARACTERISTICS OF PLUMS AS RAW MATERIAL WITH VALUABLE NUTRITIVE AND DIETARY PROPERTIES- A REVIEW’. Polish Journal of Food and Nutrition Sciences, vol. 58, no. 4, 2008, pp. 401–05.
- Lucas, Edralin. A., et al. ‘Daily Consumption of Dried Plum by Postmenopausal Women Does Not Cause Undesirable Changes in Bowel Function’. The Journal of Applied Research, vol. 4, no. 1, 2004, pp. 37–43.
- Fang, Nianbai, et al. ‘LC/MS/MS Characterization of Phenolic Constituents in Dried Plums’. Journal of Agricultural and Food Chemistry, vol. 50, no. 12, June 2002, pp. 3579–85. DOI.org (Crossref), https://doi.org/10.1021/jf0201327.
- Wallace, Taylor. ‘Dried Plums, Prunes and Bone Health: A Comprehensive Review’. Nutrients, vol. 9, no. 4, Apr. 2017, p. 401. DOI.org (Crossref), https://doi.org/10.3390/nu9040401.
- Stacewicz-Sapuntzakis, M. ‘Dried Plums and Their Products: Composition and Health Effects–An Updated Review’. Critical Reviews in Food Science and Nutrition, vol. 53, no. 12, Jan. 2013, pp. 1277–302. DOI.org (Crossref), https://doi.org/10.1080/10408398.2011.563880.