Blueberries.

Introduction


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Blueberries (Karki, 2008)
Blueberries are species of plant belonging to the genus Vaccinium; which is a member of the sub-family Vaccinioidiae, of the family Ericaceae. This family also includes such plants as cranberry, azalea, rhododendron and heather (USHBC, 2002). Blueberries contain multiple nutrients, phytonutrients, polyphenols, salicylic acid, caratenoids, fiber, folate, vitamin C, vitamin E, manganese, iron, riboflavin, niacin and phytoesterogens. Research studies have shown that blueberries are one of the richest sources of antioxidant phyto-nutrients, with higher levels of anthocyanin and phenolic contents than other fruit or vegetable. Because of their diverse range of phyto-nutrients, blueberries have a beneficial effect on human health. Antioxidant can neutralize free radicals; which are unstable molecules that cause the development of a number of diseases such as cancers, heart, cardiovascular and neurodegenerative diseases (Prior et al, 1998). They have also shown the ability to slow the aging process (Mason et al, 2007).

History


The Blueberry is one of a few native fruits of North America and was revered by the Northeast Native Americans. During the seventeenth century, settlers from England arrived in the new world to begin colonies. The colonists learnt; from the Native Americans, how to gather blueberries, dry them under the summer’s sun and store them for the winter. In time, blueberries became an important food source and were preserved, and later canned. A beverage made with blueberries was an important staple for civil war soldiers. In the 1880s, a blueberry canning industry began in the Northeast USA (USHBC, 2002).

Vacinnium Family


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Delight and Tifblue Blueberries(Karki, 2008)
Vacinnium is the family of all blueberries and includes more than 450 plants that are grown around the world. For practical and commercial purposes, there are four main species of blueberries:

V. corymbosum (Northern Highbush) – Grows wild in the forests of North America and was used to cultivate the modern highbush or cultivated blueberry industry along with the V. ashei.

V. ashei (Southern Rabbiteye) – Thrives in Southern USA and is named after the calyx of the blueberry - which resembles the eye of a rabbit.

V. angustifolium (Lowbush or ‘Wild BlueBerry’) – This variety of blueberry only reaches a height of 1 – 2 feet. They are considered ‘dwarf’ bushes and are very cold hardy; surviving in the wild as far north as Arctic North America.

V.myrtillus (European Blueberry, also known as Bilberry) – Bilberries are a low scrubby plant that grow in mountain and hilly areas all over Northern Europe and are very popular in Sweden. There are differences however between bilberries and blueberries, for example, blueberries grow in clusters of fruit where as bilberries grow in singles or pairs of berries on the bush. Their pulp is also a different colour.

Modern Blueberry Industry


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Blueberry Field, Canterbury (Karki, 2008)
The modern blueberry is a result of efforts in the 1900s by Elizabeth White and Dr. Frederick Coville to domesticate the wild highbush blueberry. They selected desirable plants from the wild forests of the Northeast USA and cultivated them to develop blueberries that could be commercially grown by farmers. Their initial breeding work resulted in the plump, juicy, sweet and easy to pick cultivated blueberries we enjoy today (USHBC, 2002). A website dedicated to the work of White and Coville can be found at www.whitesbog.org.

Today, North America is the world’s leading blueberry producer, accounting for nearly 90% of world production. Blueberry industries have also developed in South America, Australia, New Zealand and Europe. Japan and Iceland are major blueberry importing countries (USHBC, 2002).

Blueberries thrive in acid solids with a pH between 4 and 5. Cultivars require from 120 to 160 growing degree days to ripen fruit.

Antioxidant Activity


Antioxidants are phytochemicals, vitamins and other nutrients that protect cells from damage caused by free radicals. Phytonutrients (also referred as phytochemicals) are naturally occurring secondary metabolites from plants. Phytochemicals are non-nutritive plant chemicals that have protective or disease preventing properties. Plant species produces phytochemicals to protect themselves from diseases. There are more than thousands known phytochemicals produced by plant species. The major phytochemical produced by blueberries are flavanoids. Flavanoids can be found in all plant species and in different organs where they play several important roles. Flavanoids include compounds such as flavones, isoflavones, flavonones, anthocyanins, and catechins which have strong antioxidant capacity (Priori et al, 1998). Blueberries contain significant quantities of anthocyanin in their fruit - the pigment that makes blueberry blue.

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Chemical Structure of Anthocyanins
Anthocyanins are powerful antioxidants which gives red, blue and purple colour to blueberry fruit. The darker, deeper blue and red fruits have the highest anthocyanin content; therefore they contribute the most potent antioxidant source. Differences in fruit coloration from white to red to blue to purple are related to the concentration of anthocyanin present in their skin (Ballinger et al, 1981). The colour blue attracts birds (helping in seed dispersal) and acts as a cellular support materials (Riihinen et al, 2008). Riihinen et al (2008) cited that blueberries also serves as a signal molecule in sexual reproduction and protects the plant against UV radiation and as well as participate in plant microbe interation and defence response.

Anthocyanins contain naturally occurring plant chemicals called polyphenols with very high antioxidant characteristics. Antioxidants work by donating an electron to free radicals to convert them to harmless molecules. This protects cells from oxidative damage that leads to aging and various diseases. Fresh blueberries contain 15 different anthocyanins (as well as vitamin C).

Measurement of Antioxidant Activity

Oxygen radical absorbance capacity (ORAC) assay has been used widely in measuring the net resultant antioxidant capacity (or peroxyl radical absorbance capacity) of blueberries. Other methods used to measure free radical scavenging activities of food is photochemiluminescence (PCL) assays (Cho et al, 2005), superoxide anion scavenging activity (SASA) and free radical scavenging activity (DPPH). Prior et al (1998) used four varieties of Vaccinium sp; they demonstrated that ORAC was linearly related to the anthocyanin and total phenolic contents. However, this relationship was not confirmed in Vaccinium varieties and other berries (Rossi et al, 2003). Since phyotochemical antioxidants differ in their ability to scavenge different free radicals, it is important to understand the capacity of antioxidants by multiple assays using different biologically relevant radical sources.

Research

Mason et al (2007) performed a research on “Antioxidant activity and total phenolic content in four blueberries cultivars grown in NZ”.

Mason et al (2007) measured total phenolic content and antioxidant capacities (using SASA and DPPH) of four cultivars of blueberries grown in Canterbury, New Zealand. Off the four cultivars studied: Burlington, Alanta, Stanley and Jersey; total phenolic content ranged from 230 ± 18 to 297 ± 63mg GAE.100g?1. It was discovered that Burlington blueberries had significantly (P>0.001) higher total phenolic content than the three other varieties. Total phenolic content was compared for both fresh weight and freeze dried; the results were not statically different. This suggests that the nutritional benefits of blueberries are similar when they are fresh or frozen. Antioxidant capacities of the four cultivars were only statistically significant when measured by SASA; the results were not significantly different when measured by DPPH. The author concludes that total phenolic content of New Zealand blueberries is similar to blueberries grown in the US, suggesting that nutritional content is not affected by environmental growing conditions and genotype (as hypothesized by Howard et al, 2003 and Prior et al, 1998 cited in Mason et al, 2007). Priort et al (1998) reported that bilberries (the European Blueberry) contain the highest amounts of anthocyanin in comparison to other berries (including those of V.agustifolium). The amount of anthocyanin in bilberries ranges from 300 to 698mg/100 g and increase during the ripening process.

Nutritional and Popularity


In the past, blueberries (along with the leaves and roots) were used for medicinal purposes, as a dye for baskets and cloth, used to treat coughs and their juice was said to be good for the blood. In food preparation, dried blueberries were added to stews, soups and meats (and even beef jerky!) (USHBC, 2002).

Blueberries are very popular as an ingredients or when consumed fresh. As previously mentioned, blueberries are rich in vitamins C and E. They are also rich in potassium and folate and low in fat and sodium – please see table below (USDA, National Nutrient Database, 2004). Blueberries are processed into a number of different forms such as: canned, liquid, frozen and freeze-dried.

Popular products containing blueberries are jellies, jams, pies, juice and flavored drinks. They are baked into muffins and also used as a delicacies and snacks. Frozen or free-dried blueberries are often used in yogurt, ice-cream, cake and fruit desserts. Because of the high level of antioxidant activity found in blueberries and the ability to slow the anti-aging process, nutraceutical and pharmaceutical industries have started using blueberries in their nutritional and skin care products.

Demand for the production of blueberries continues to increase as consumers become aware of the health benefits of phenolic compounds and antioxidants. USDA reports (as cited by Pennigton Nutrition Series, 2007) indicate that between the years of 1994 and 2003, annual US consumption of fresh blueberries rose approximately 1.6 times.

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Source: The George Matjlan Foundation

Blueberry Products available in New Zealand

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Health Benefits


As previously mentioned, research studies have discovered that blueberries have many potential health benefits, these include:

Cancer Prevention

Research studies in the US by the Agricultural Research services have recently revealed that blueberries (as well as strawberries and raspberries) contain chemicals that decreased the growth of cervical and breast cancer cells by a considerable percentage. Ellagic acid is another antioxidant present in blueberries that has shown to prevent cancer development. Research suggests ellagic acid blocks the metabolic pathways that can promote cancer

Brain Health

In laboratory animal studies, researchers have found that blueberries help protect the brain from oxidative stress and may reduce the effects of age-related conditions such as Alzheimer's disease or dementia.

Anti-aging

Various laboratories have demonstrated that fruits and vegetables (such as blueberries and strawberries) high in antioxidant and anti-inflammatory activity can prevent the occurrence of the neurochemical and behavioral changes that occur in aging.

Others

Blueberries can also help prevent urinary tract infection, reduce cystitis, enhance the memory, improve eyesight due to having very high concentration of anthocyanin and have also been linked to reduce the risk of heart diseases. In addition to containing ellagic acid, blueberries are high in the soluble fiber pectin - which has been shown to lower cholesterol and to prevent bile acid from being transformed into a potentially cancer-causing form.

In Europe, a number of studies have shown that blueberries and bilberries improve eyesight; this is due to the high concentration of anthocyanin found in the fruit.

References

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