Neither American nor blue elderberry has been evaluated for their volatile aroma composition, which limits the understanding of how these subspecies may perform and be accepted by consumers in the same formats as European elderberry. Analytical assessments of the elderberries and products using the elderberries, in addition to sensory panels would be useful information for product developers and should be performed when cultivars or genotypes are being selected for cultivation and use in commercial products. Elder flowers are frequently used in beverages and food products, including but not limited to teas, syrups, lemonades, liqueurs, wines, jams/marmalades, and tonic water. They are also used for flavoring in yogurt, coated almonds, lozenges, and confectionary goods, to name a few. Furthermore, elder flower can now commonly be found in soaps, lotions, and candles, thus consumers, especially in the United States are becoming more familiar with elder flowers, which have been well-known in Europe for generations. These recent studies support the long history of use of elder flower by the Lumbee tribe in North Carolina, who use elder flower as a treatment for skin cancer by soaking flowers in witch hazel for a week then applying that to the skin. The main compound in elder flowers, like elderberries, is water, and is found in similar concentrations .Glucose, fructose,low round pots and sucrose make up the main sugars found in elder flower.While European elder flowers have a roughly equal amount of these sugars, elder flowers of the blue elderberry have a much higher level of fructose than glucose or sucrose.
However, there has only been one study to measure these compounds in elder flowers, and more studies are needed to know if this trend occurs across each of the subspecies. There is limited data on these compounds across the three subspecies of interest, such as no information on the American elderberry; thus, few comparisons can be made. Minerals and vitamins have been evaluated in European elder flowers. Minerals include calcium, magnesium, copper, zinc, and manganese. Calcium is the most concentrated mineral with an average of 2955.9 ± 272.7 µg g-1 across several wild and cultivated samples and magnesium is the next most concentrate mineral at an average of 1200.2 ± 453.6 µg g-1 . Vitamin C has only been measured in elder flower syrup, ranging from 22.47 ± 0.06 mg L-1 to 46.17 mg L-1 . Elder flowers of the European subspecies have been evaluated several times for their phenolic profile. Dominant compounds in the flavonol rutin and neochlorogenic acid. Concentrations can vary greatly, just like many of the other compounds already explored in this review. Growing and harvest conditions6 or extraction parameters can impact the final concentrations reported. Significant differences in phenolic concentrations have been found between cultivars, such that the concentration of rutin ranged from 11.6 to 42.3 mg g-1 dry weight and neochlorogenic acid ranged from 10.1 to 20.7 mg g-1 dry weight among the 16 genotypes. The coefficient of variation was greater than 10% for all of the compounds measured, including nine phenolic acids and six flavonol glycosides. American elder flowers have also been studied for their concentration of rutin and chlorogenic acid which generally align with the European elder flower profile, except that the primary phenolic acid was chlorogenic acid instead of neochlorogenic acid.
American elder flower appears to contain a different chlorogenic acid isomer than the European elder flower, which has mainly neochlorogenic acid. Furthermore, 12 cultivars were sampled for the study, which showed high variability in concentration of the two compounds measured. Rutin concentrations ranged from 4637 to 8111 mg kg-1 while chlorogenic acid concentrations ranged from 1180 to 3064 mg kg-1 , showing that key phenolic compounds can be more than double in some cultivars. The concentration of these two compounds did not appear correlated, as the correlation coefficient was only 0.018. While there have been several studies measuring the CG content in elderberries of different subspecies, the data available on elder flower CG content is limited. In fact, only one study has published data on this area to date and it focused on European elder flowers. A study comparing growing locations at multiple altitude levels to determine impact on phenolic compounds and cyanogenic glycosides found that CG concentrations in elder flowers ranged from 1.23 ug g-1 to 18.88 ug g-1 , generally increasing as the altitude increases. 6 Sambunigrin was the only CG measured and compared to the berries of the same plants in this study, elder flowers contained more CGs than elderberries. 6 Elder flowers from the American subspecies nor the blue subspecies have been analyzed for their CG content. As consumer concern for this toxic group of compounds remains high, it would increase confidence of consumers to utilize the elder flowers of these other subspecies if data was available on the CG concentrations of these flowers. Elder flowers and elder flower products have been investigated for their volatile profile.
A direct comparison is difficult to make from the syrups, which have other ingredients like sugar or lemons, to the plain flower extracts, but due to the high popularity of elder flower syrups, the results of those studies are included here as well. In studies of the European elder flower without any additional food ingredients, linalool and linalool derivates, such as -linalool pyranoxide and cis-linalool oxide, have frequently been identified as prominent.The aroma of linalool, the main aroma compound in lavender, can be described as citrus, fruity, floral, and woody. 80 The age of the flower when harvested as well as how the flowers are stored after harvest can greatly impact the volatile profile. As expected from the other data on inter-cultivar variation, the volatile profile is heavily influenced by the cultivar. 81 For example, wild elder flower had twice as much rose oxide and more linalool oxide than the other 12 cultivars. While this could be a challenge for manufacturers that use elder flower in products to have a consistent aroma from batch to batch, it also allows for more selectivity to find a cultivar that matches desired organoleptic properties in the product. American elder flowers have not yet been evaluated for their volatile profile, nor have blue elder flowers. As global warming and water scarcity issues continue to impact food systems, fire-resilient and drought-tolerant plants will become more important for supplying nutrient-rich foods . Wildfires throughout the western United States are becoming more common and more serious as seasons are hotter and drier. California has been experiencing unprecedented levels of wildfires, including over 1.9 million acres burned in 2018, over 4.2 million acres burned in 2020, and over 2.5 million acres in 2021. One native and fire-resilient plant is the blue elderberry , which grows wild throughout the western United States and has become a popular choice to grow in hedgerows. The blue elderberry is drought-tolerant, and the roots of the blue elderberry can survive fires to regrow the next season to continue providing valuable flowers and fruit, making it an ideal choice to plant in regions of California and American West often stricken by wildfires. While European and American elderberries have been studied for decades, there is currently little information on the subspecies native to the western region of North America, S. nigra ssp. cerulea ,plastic pots 30 liters known as blue elderberry due to a white-colored bloom on the exterior of the berry which makes it appear blue. In California, it grows wild in riparian ecosystems near rivers and streams 86 , but is also planted in hedgerows on farms to improve water, air, and soil quality, in addition to providing a habitat for birds, pollinators, and other beneficial insects . The plant can grow several meters tall and wide and flowers from May to August, with peak fruit ripening throughout July and August. While elderberry prefer moist soil and some hedgerows may receive some irrigation during the summer months, most are not irrigated once the hedgerow has been established, about 2-4 years . That is one of the benefits of using native and drought-tolerant plants, as they can better withstand the natural climate without excess resources. Elderberries have a long history of use by Native Americans and Europeans in foods, beverages, and herbal medicines. Research exploring links between elderberry consumption and health has increased dramatically, particularly in the past decade.
Numerous in vitro and in vivo studies demonstrate that elderberries have potent antioxidant, antibacterial, and antiviral properties. Results of two randomized, double-blind, placebo-controlled clinical trials suggest that elderberry supplements reduce the duration and severity of cold symptoms . Roscheck et al. identified two non-anthocyanin flavonoids in elderberry extract that inhibited viral ability to infect host cells when bound. While most bio-activity of elderberries is assumed to result from the phenolic compounds like anthocyanins, the high-molecular weight fraction of concentrated elderberry juice was found to contain acidic polysaccharides that had potent effects against the human influenza virus . The health-promoting properties of elderberry have led to recent increases in its use in products such as supplements, syrups, gummies, and teas, as well as wine and jams. During the COVID-19 pandemic, elderberry supplements gained wide attention because of potential anti-viral activities; however, there is no strong clinical evidence that elderberry could be beneficial in preventing or treating COVID-19. The market for elderberries is expected to continue to increase, as the sales of herbal dietary supplements was over $11 billion in 2020, a 17.3% increase from 2019. Elderberry was the top selling herbal supplement, with sales over $275 million, as consumers became more interested with supporting their immune systems 9 . In addition to the interest in elderberry as an ingredient in functional foods, elderberry can be an excellent source of natural coloring agents for food and beverage applications due to the high content of red and purple anthocyanins . Characterization of the chemical composition, functional properties, and impact of processing on the bio-active compounds in elderberry is largely limited to S. nigra ssp. nigra and, to a lesser extent, S. nigra ssp. canadensis. S. nigra ssp. nigra is commonly referred to as the European black elderberry, which has many established cultivars, such as “Haschberg” and “Samyl”, and it has an established market. The European elderberry is the most frequently used subspecies in commercial elderberry-based products and has been extensively studied for its composition, anthocyanin stability , and health benefits in European black elderberry-based products . S. nigra ssp. canadensis is commonly referred to as the American elderberry, a subspecies native to the eastern and central regions of North America. There are several cultivars of the American elderberry, including “Johns” and “Bob Gordon”. The American elderberry, which is utilized in small-batch products, has also been evaluated for its composition and health-promoting properties. The acreage grown of this subspecies has been increasing rapidly and there is a goal to grow over 2,000 acres by 2025, according to the Midwest Elderberry Cooperative. Currently, there is no information on the chemical composition of the fruit of the blue elderberry . With the recent increase in demand for elderberry, blue elderberry grown in hedgerows may be an additional and valuable source of bio-active phenolics and natural colorants. The objective of this study was to determine the moisture content, soluble solids, pH, titratable acidity, and establish the anthocyanin and phenolic profiles of blue elderberries grown in Northern California to support the use of this robust, native crop in commercial products. Five grams of frozen berries were mixed with 25 mL of in a conical tube, which was then homogenized for 1 min at 7,000 rpm . The mixture was stored at 4 °C overnight, then in the morning, centrifuged at 4,000 rpm for 7 min. The supernatant was used directly for analysis. Three pooled samples were made for each hedgerow, each consisting of even amounts of berries from three distinct shrubs. Each pooled sample was extracted once to give 3 biological replicates, and each extract was run in duplicate . Averages concentrations for compounds were determined across the hedgerow in mg per 100 g FW. The concentration of phenolic compounds in blue elderberry followed the method by Giardello et al. with some modifications. Briefly, samples were analyzed via reversed-phase liquid chromatography on an Agilent 1200 with a diode array detector and fluorescence detector .