Central Composite Design Applied to Optimize the Hydroalcoholic Extraction of Bilberry (Vaccinium Myrtillus L.) Fruits

The present study optimized the hydroalcoholic extraction conditions to maximize the anthocyanin content, total phenolic content and antioxidant activity of bilberry extracts. Optimal conditions with regard to ethanol concentration (X₁: 8.17–91.83% v/v), extraction time (X₂: 8.27–41.73 days) and solid‐to‐liquid ratio (X₃: 0.38–1.22, w/v) were identified using central composite design combined with response surface methodology. The results showed a good fit with the proposed second‐order polynomial models for all responses (R² > 0.964). Among the three extraction parameters, ethanol concentration had the main impact on the extraction efficiency for all responses. The optimum extraction conditions that maximized total anthocyanin content are ethanol concentration 91.83%, solid‐to‐liquid ratio 1.22 and extraction time 23.5 days, whereas maximum total phenolic content under the same conditions is reached after 28 days of extraction. Tristimulus colorimetry was used to evaluate color properties of bilberry extracts, and correlations were assessed between CIELab indices, anthocyanin content, phenolic content and antioxidant activity. PRACTICAL APPLICATIONS: Bilberries possess high antioxidant potential due to their richness in phenolics, especially anthocyanins, which occur not only in the skin but throughout the red fruit flesh. These compounds can be efficiently extracted with ethanol or aqueous‐based ethanol solutions in order to obtain bilberry liqueur, a noble, full of color and flavor drink, with potential health benefits. In this study, optimum conditions for the hydroalcoholic extraction of bilberries were determined. Alcohol concentration, extraction time and solid‐to‐liquid ratio were the extraction parameters investigated in order to optimize the total anthocyanin content, total phenolic content and antioxidant activity of bilberry extract. Optimal operating conditions to maximize the efficiency of the extraction can be used in handcrafted or industrial application.