Research on the mineral composition of cultivated and wild blueberries and cranberries

A. Karlsons*, A. Osvalde, G. Čekstere and J. Pormale

Institute of Biology, University of Latvia, Laboratory of Plant Mineral Nutrition, Miera street 3, Salaspils, LV-2169 Salaspils municipality, Latvia
*Correspondence: andis.karlsons@lu.lv

Abstract:

European cranberry (Vaccinium oxycoccos L.) and European bilberry (Vaccinium myrtillus L.) are among the most popular wild-harvested fruits in Latvia, traditionally used in folk-medicine and food. The commercial cultivation of American cranberry (Vaccinium macrocarpon Ait.) and highbush blueberry (Vaccinium corymbosum L.) was successfully started during last 20 years. With a berry production increase due to considerable hectarage of plantings and growing consumer interest in health-improving foods cultivated blueberries and cranberries have found a place in a daily intake as an excellent source of phenolic and nutritive compounds, vitamins and minerals. As the chemical composition of Vaccinium spp. has an important implication on human health, detailed information on the nutritional content of berries are of special importance. The aim of this study was to compare the contents of twelve biologically essential elements (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo, B) in berries of four Vaccinium species: cultivated and wild blueberries (Vaccinium corymbosum and Vaccinium myrtillus) and cranberries (Vaccinium macrocarpon and Vaccinium oxycoccus). Together 136 (leaf and berry) samples were collected from 7 main cranberry and blueberry producing sites and 17 native woodland areas and bogs in Latvia. A comparison of wild and cultivated species showed similar concentrations for the macroelements K, Ca and S in cranberry and N, P in blueberry fruits. While statistically significant differences were found for N, P and Mg in case of cranberries and Ca, K, Mg and S for blueberries. The research revealed statistically significant differences of most micronutrients in cultivated and wild berries. Plant leaf and fruit analysis revealed the organ-specific distribution of mineral elements in all species studied. In most of the cases, leaf analysis supported concentration differences in fruits.

Key words:

mineral composition of fruits, Vaccinium corymbosum, Vaccinium macrocarpon, Vaccinium myrtillus, Vaccinium oxycoccus

Comparison of methods of extraction of phenolic compounds from American cranberry (Vaccinium macrocarpon L.) press residues

L. Klavins, J. Kviesis, M. Klavins*

University of Latvia, 19 Raina Blvd., LV–1586, Riga, Latvia
*Correspondence: maris.klavins@lu.lv

Abstract:

American cranberries (Vaccinium macrocarpon L.) contain significant quantities of
various phenolic compounds. Most of these compounds are recovered when berry juice is
produced. However, a considerable part of polyphenols remain in berry press residues and are
discarded as food industry waste. The aim of the study was to compare the methods of extraction
of polyphenols (ultrasound, microwave-assisted, Soxhlet) from press residues of American
cranberry. The impact of main extraction parameters (e.g., extraction time, solid/solvent ratio,
solvent type) on the yield of extracted polyphenols. Ultrasound-assisted extraction showed the
highest potential from all studied methods, given its fast, convenient use and low cost. Aqueous
ethanol and methanol in the presence of acid (anthocyanin extractions should be assisted with
trifluoroacetic acid, polyphenol extractions – with HCl) were assessed as the best solvents for
extraction. The obtained extracts were characterised using the Folin-Ciocaulteu method for
determination of total phenolics and the pH-differential method for determination of total
anthocyanins, and UPLC–PDA was used to determine the content of individual anthocyanins.
Cyanidin-3-O-arabinoside, peonidin-3-O-galactoside, peonidin-3-O-glucoside and peonidin-3-
O-arabinoside were identified as the main anthocyanins in cranberry press residue extracts.

Key words: