Wild Blueberry Concentrations: Antioxidants, Vitamins and Minerals
Created by: Lily Calderwood, PhD, Extension Wild Blueberry Specialist & Brogan Tooley, Research Assistant
Reviewed by Dorothy Klimis-Zacas, PhD, FACN, Professor of Clinical Nutrition
Given the strong interest in the health benefits of wild blueberries (Vaccinium angustifolium Ait) and the creation of new wild blueberry products, this factsheet serves as a chemical composition summary for berries and leaves of this plant.
Wild blueberries are high in vitamins, minerals, micronutrients, fiber and antioxidants. One of the most abundant antioxidants in wild blueberries (when ripe) are the flavonoid compounds anthocyanins (Gibson et al. 2013). Anthocyanins are located in the skin and responsible for the blue pigmentation and some associated health benefits. As researches, stakeholders and consumers of this nutritional wild food crop, it is important to consider the vitamin and mineral concentrations from field to human body.
Due to the low soil pH of wild blueberry fields (4.0-5.0), excess minerals are available for plant uptake, while other required plant nutrients, such as nitrogen, are less available. Wild blueberry plants have evolved to tolerate metals in the soil when other competing plants have not (Smagula and Litten 2003). Naturally occurring trace metals (minerals) are consequently taken up by the crop and stored in the stem, leaves and berries (Smagula and Litten 2003; Yarborough et al. 2017).
- Phytochemicals – Biologically active compounds found in plants which include polyphenols.
- Polyphenols – Are a group of compounds found in plants that have antioxidant effects in addition to other human health benefits such as improved digestion, vascular function, brain function, and inflammation. They have also been found to be protective for eye and tooth health, heart disease, and certain cancers. One of these compounds is the flavonoid anthocyanin.
- Anthocyanins – Pigment compounds found in red, purple, blue, and black plants. These are the pigments that give blueberries their blue skin and sugar maples their red leaves in the fall. These are compounds with antioxidant effects that belong to a larger group of molecules called Flavonoids.
- Antioxidant – A characteristic of some plant compounds that slows down or inhibits oxidation in biological organisms. Oxidation causes cell damage in both plants and humans. Plants produce these compounds to protect themselves against insect feeding, disease infection, and environmental stress. Research on humans has found that these compounds are also beneficial in protecting our cells from oxidizing damage
- What are the average vitamin and antioxidant concentrations, and corresponding health benefits of wild blueberry?
- What are the mineral concentrations in wild blueberry?
- At what concentration would these minerals be of concern to human health?
- Are mineral concentrations affected by processing?
- Do antioxidant concentrations deteriorate with time or processing method?
The vitamin concentrations in wild blueberries have been documented by Bushway et al. (1983) and Yang and Atallah (1985). Bushway et al. documented concentrations of vitamins A and C, Niacin, Riboflavin and Thiamin in fresh berries with concentrations of 0.46, 68, 13, 0.54, and 23.0, µg/g respectively. Yang and Atallah quantified vitamins A, C and niacin in frozen berries with concentrations of 0.36, 7.1 and 14.2 µg/g respectively. The large deviation in vitamin C in the Yang and Atallah study was attributed to the freezing and storing of the berries, as well as genetic variation in clones. Overall, frozen berries have been shown to have more vitamin A and less vitamin C when compared to fresh wild blueberries. While fresh wild blueberries have also exhibited decreases in vitamin C with storage greater than 8 days (at 20 and 30 °C) (Kalt et al. 1999).
One ½ cup, or 150 ripe wild blueberries, can provide 200-400mg of polyphenols (Gibson et al. 2013). Lowbush blueberry has been found to have greater anthocyanin content than highbush blueberry, raspberry and strawberry, but also the lowest vitamin C when compared to those 3 berries (Kalt et al. 1999). Polyphenols, which are inside the plant and have antioxidant properties, were shown to change in concentration with the ripeness (maturity) of the fruit. Gibson et al. (2013) found ripe berries to have a total antioxidant capacity of 125 (mg TE/g DW) using Ferric Reducing Antioxidant Powder (FRAP), where TE are Trolox Equivalents and DW is dry weight. Here, green berries had higher total antioxidant capacity (with antioxidants other than anthocyanin) from polyphenols when compared to red, blue and “overly ripe” berries, suggesting the potential for value-added use of green berries. Anthocyanin concentration increased with berry ripeness (Gibson et al. 2013).
Corresponding Health Benefits
The presence of antioxidants in one’s diet prevents oxidative stress caused by the buildup of “free radicals”, associated with cancer, heart disease, diabetes, aging, and more. For more information on the health benefits of wild blueberry antioxidants, please visit: http://www.wildblueberries.com/health-research/antioxidants/
As effective colonizers of disturbed sites, wild blueberries are tolerant of extreme environments with acidic soils (low pH) and the presence of minerals (Sheppard, 1991; Smagula & Litten, 2003). The optimal soil pH for wild blueberry is 4.5, however, fields can range from 3.9 to 5.3 (Smagula & Litten, 2003). Sulfur is applied as a weed management tool where the pH is lowered to a point where wild blueberry can live yet weed species struggle. Lower pH (acidic) soils in wild blueberry fields have been linked to greater mineral concentrations in the soil subsequently affecting the chemical composition of the foliage (Hall et al. 1964).
Table 1. Average wild blueberry mineral concentrations found in the leaf, stem and berry by Sheppard (1991) and berry mineral concentrations identified by Bushway et al. (1983) and Yang and Atallah (1985). An additional column includes the Daily Food Values (DV) established by the FDA for adults (children’s limits are lower) from the Dietary Supplement Label Database (DSLD, unpublished, 2019 https://www.dsld.nlm.nih.gov/dsld/dailyvalue.jsp). One hundred berries is approximately 1/3 cup.
|Sources||Sheppard 1991||Bushway et al. 1983||Yang & Atallah 1985||DSLD/ FDA|
|Leaf||Stem||Dry Berry||Fresh Berry||Per 100 Berries||Fresh Berry||Frozen Berry||Daily Values|
|dry (µg/g)||dry (µg/g)||dry (µg/g)||wet (µg/g)||µg/100 berries||wet (µg/g)||wet (µg/g)||µg/day|
*Daily values for Aluminum in food are not specified by the FDA, this range comes from Yokel 2008.
**NA indicates Not Available, for these mineral limits have not been set or they have been deemed safe (in the case of sulfur).
Concentrations of Concern
Based on the FDA Daily values listed above (Table 1), the berries would need to be concentrated between 3 and 900 times to reach daily consumption limits. Mineral concentrations proximal to daily values include Copper and Manganese. These estimates are based on the mineral concentration in 100 berries, or 1/3 cup (provided by Sheppard 1991); the number of berries in a concentrate or the daily consumption amount should also be considered when processing.
Effects of Processing
It’s been documented that heating fruits and vegetables decreases the vitamin activity in the food through vitamin oxidation (Yang and Atallah 1985; Lopez et al. 2010). Vitamin C has been found to degrade in blueberry with temperatures exceeding 80°C (Lopez et al. 2010). Yang and Atallah (1985) looked at how these concentrations change with various methods of drying (freeze dry, forced air, vacuum oven, and micro-convection). Of the four drying methods tested, vitamins A and C decreased significantly from the control (frozen) with all processing methods EXCEPT freeze-drying. This decline in vitamin content with particular drying methods was attributed to the use of heat. Niacin also significantly decreased under all drying methods except the micro-convection compared to the control (frozen). Individual quick freezing, however, has been associated with the retention of vitamin C, phenolics and anthocyanin capacity (Review: Kalt et al. 2019).
Interestingly the mineral concentrations were not affected by drying treatments with the exception of Magnesium, which significantly decreased with freeze drying and sodium which increased with micro-convection (Yang and Atallah 1985). Although the mineral concentrations in wild blueberry were unchanged with various drying methods, it’s important to keep in mind the relative portion increase when changing the physical state of the berries.
When processing wild blueberry there is a high possibility for the loss of anthocyanins depending on the storage or processing method (Routray & Orsat 2012, Donahue, 2000). All factors listed below (compiled from Routray & Orsat, 2012; Kalt et al. 2019; Yang and Atallah 1985) lead to a loss in anthocyanin. In some cases, an increase in anthocyanins was observed (fermentation; Routray & Orsat, 2012).
Factors leading to the greatest anthocyanin loss:
- Leakage: Result of soft/punctured berries or berry age
- Heat: Greater than 158°F (70°C)
- Osmotic dehydration
- Juice, jam or extracts stored at room temperature
Methods found to reduce anthocyanin loss during storage and increase shelf life:
- Quick Freezing
- Freeze-drying Low heat (if cooking is required), 104-140°F (40-60°C)
- Modified Atmosphere Packaging (MAP)
- Pasteurization techniques
- Radiant zone drying
- Steam blanching
- The use of multiple drying methods in combination
*Cooling has been found to increase phenolic synthesis which increases anthocyanin content.
**Fermentation has been found to increase antioxidant capacity (Martin and Martar, 2005).
Bushway, R.J., D.F.M. Gann, W.P. Cook, And A.A. Bushway. 1983. Mineral and Vitamin Content of Lowbush Blueberries (Vaccinium angustifolium Ait.). J. Food Sci. 48(6):1878–1878. doi:10.1111/j.1365-2621.1983.tb05109.x.
Donahue, D. W., Bushway, A. A., Smagula, J. M., Benoit, P. W., & Hazen, R. A. 2000. Assessment of Pre-Harvest Treatments on Maine Wild Blueberry Fruit Shelf-Life and Processing Quality. Small Fruits Review. 1:1, 23-34, DOI:10.1300/J301v01n01_04
DSLD. 2019. Daily Value Reference of the Dietary Supplement Label Database (DSLD). Available at https://www.dsld.nlm.nih.gov/dsld/dailyvalue.jsp (verified 2 December 2019).
Gibson, L., Rupasinghe, H. P. V., Forney, C. F., & Eaton, L. 2013. Characterization of changes in polyphenols, antioxidant capacity and physico-chemical parameters during lowbush blueberry fruit ripening. Antioxidants, 2(4), 216–229. https://doi.org/10.3390/antiox2040216
Hall, I. V., Aalders, L. E., Townsend, L. R., 1964. The effects of soil pH on the mineral composition and growth of the lowbush blueberry. Canadian Journal of Plant Science. 44:433-438.
Kalt, W., C.F. Forney, A. Martin, and R.L. Prior. 1999. Antioxidant Capacity, Vitamin C, Phenolics, and Anthocyanins after Fresh Storage of Small Fruits. Journal of Agricultural and Food Chemistry 47(11):4638–4644.
Kalt, W., A. Cassidy, L.R. Howard, R. Krikorian, A.J. Stull, F. Tremblay, and R. Zamora-Ros. 2019. Recent Research on the Health Benefits of Blueberries and Their Anthocyanins. Advances in Nutrition.
López, J., Uribe, E., Vega-Gálvez, A., Miranda, M., Vergara, J., Gonzalez, E., & Di Scala, K. (2010). Effect of air temperature on drying kinetics, vitamin c, antioxidant activity, total phenolic content, non-enzymatic browning and firmness of blueberries variety óneil. Food and Bioprocess Technology, 3(5):772–777. https://doi.org/10.1007/s11947-009-0306-8
Martin, L.J., and C. Matar. 2005. Increase of antioxidant capacity of the lowbush blueberry (Vaccinium angustifolium) during fermentation by a novel bacterium from the fruit microflora. Journal of the Science of Food and Agriculture 85(9):1477–1484.
Routray, W., & Orsat, V. 2011. Blueberries and Their Anthocyanins: Factors Affecting Biosynthesis and Properties. Comprehensive Reviews in Food Science and Food Safety, 10(6):303–320. https://doi.org/10.1111/j.1541-4337.2011.00164.x
Sheppard, S. C. 1991. A field and literature survey, with interpretation, of elemental concentrations in blueberry (Vaccinium angustifolium). Canadian Journal of Botany, 69(1):63–77. https://doi.org/10.1139/b91-010
Smagula, J. M., & Litten, W. 2003. Can lowbush blueberry soil pH be too low? Acta Horticulturae, 626:309–314. https://doi.org/10.17660/ActaHortic.2003.626.43
USDA & NASS. 2019. USDA/NASS, National Agricultural Statistics Service. QuickStats Ad-hoc Query Tool. Available at https://quickstats.nass.usda.gov/ (verified 10 December 2019).
Yang, C.S.T., & W.A. Atallah. 1985. Effect of Four Drying Methods on the Quality of Intermediate Moisture Lowbush Blueberries. J. Food Sci. 50(5):1233–1237. doi:10.1111/j.1365-2621.1985.tb10450.x.
Yarborough, D., Drummond, F., Annis, S., & D’Appollonio, J. (2017). Maine wild blueberry systems analysis. Acta Horticulturae, 1180:151–159. https://doi.org/10.17660/ActaHortic.2017.1180.21
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