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Leaves of bilberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea L.) are potential raw materials for food and health care products. Targeted (HPLC-DAD, HPLC-MS, and GC-FID) and nontargeted ((1)H NMR) approaches were applied to study the metabolomic profiles of these leaves. Chlorogenic acid was the major phenolic compound in bilberry leaves and arbutin in lingonberry leaves. Flavonol glycosides were another major group of phenolics in bilberry [5-28 mg/g DM (dry mass)] and lingonberry (15-20 mg/g DM) leaves. Contents of fatty acids were analyzed using GC-FID. The changes in the metabolomics profile during the season were apparent in bilberry but not lingonberry leaves. Negative correlation was found between the contents of lipids and phenolics. The consistency between the key results obtained by targeted and nontargeted analyses suggests nontargeted metabolomic analysis is an efficient tool for fast screening of various leaf materials.

Malolactic fermentation using sea buckthorn (Hippophaë rhamnoides) juice as raw material was performed with six different strains of Lactobacillus plantarum. Increasing juice pH from 2.7 to 3.5 or adapting cells to low pH (i.e., acclimation) prior to inoculation allowed malolactic fermentation with all tested strains. Moreover, reducing pH of the growth medium from 6 to 4.5 with l-malate had little or no impact on biomass production. Volatile profile of sea buckthorn juice was analyzed with HS-SPME–GC–MS before and after fermentation. A total of 92 volatiles were tentatively identified and semi-quantified from sea buckthorn juice, majority of which were esters with fruity odor descriptors. Esters and terpenes were decreased in both inoculated and control juices during incubation. Microbial activity increased the levels of acetic acid (vinegar like), free fatty acids (cheese like), ketones (buttery like), and alcohols with fruity descriptors. Conversely, aldehydes associated with “green” aroma were decreased as a result of fermentation. Juices fermented with DSM 1055 had the highest acid and alcohol content, while fermentation with DSM 13273 resulted in the highest content of ketones. Compared to inoculation with other strains, fermentation with strains DSM 16365 and DSM 100813 resulted in rapid malolactic fermentation, less production of volatile acids, and lower loss of esters and terpenes important for natural sea buckthorn flavor.

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Tannic and gallic acids, extracted from Chinese gallnut, were applied as copigments to bog bilberry syrup wine with two different mass ratios of 1:2.5 and 1:6 of anthocyanin to copigment. The effect of copigmentation on anthocyanins and the changes in non‐anthocyanin compounds and color characters during 6 months of aging were studied. Addition of copigment significantly helped to retain redness while reduced increase in the yellow shade and lightness. After 6 months of aging, the syrup wines with added copigments had 1.4–1.8 times higher total anthocyanin content compared to the control. The percentage of polymeric anthocyanins in copigment treated wines was lower than in control wine. Oppositely, the copigment treated wines possessed a higher percentage of copigmented anthocyanins than the control. The highest value of redness, the lowest percentage of polymeric anthocyanins and the highest percent of copigmented anthocyanins were presented in the wines treated with a high dosage of gallic acid. Practical applications Bottle aging shows a negative effect on the appearance of bog bilberry syrup wine. Copigmentation between anthocyanins and copigments is an alternative approach to prevent the loss of color during aging. However, the high expense of pure copigments limits the application of this protocol in wine industry. The cheaper copigments of tannic acid and gallic acid, extracted from Chinese gallnut, were used in the present study and presented positive effects on remaining red hub of bog bilberry fermented products through the enhancement of anthocyanin copigmentation. The current study provides new insights on exploiting somewhat poorly utilized bog bilberry byproduct in wine industry. The findings also verify the practicable of the economical copigments of Chinese gallnut extracted tannic and gallic acids in bog bilberry fermented products. On the other hand, observations made with bog bilberry in this study may be exploited with other berry materials, as well.