EFFECT OF ETHANOL CONCENTRATION, SOLID:LIQUID RATIO, AND EXTRACTION TIME ON THE RECOVERY OF BIOACTIVE COMPOUNDS FROM BLACKBERRY POMACE

The recovery of anthocyanins from agro-industrial residues has attracted increasing attention due to their functional benefits and diverse applications in the food industry. These flavonoids, abundant in blackberries, possess well-documented antioxidants and other health-promoting properties. In response to the need for waste reduction and add value to food by-products, this study evaluated the effect of ethanol content and solid:liquid ratio on the extraction of bioactive compounds from blackberry pomace, aiming at its potential use as a functional ingredient or natural agent, such as a colorant, in food products. Hydroethanolic extraction assisted by magnetic stirring was carried out at room temperature for 90 minutes, followed by centrifugation at 4000 rpm for 15 minutes. The centrifuged extracts were then stored at –20 °C. A central composite rotational design (CCRD) was applied considering solid:liquid ratio (1:3 to 1:17) and ethanol concentration (8–92%) as independent variables. The response variables were phenolic compound concentration (PCC, Folin-Ciocalteu method), anthocyanin concentration (AC, pH differential method), and antioxidant activity (AA, assessed by ABTS and DPPH assays). PCC values ranged from 704.2 ± 5.4 to 2859.1 ± 42.3 mg GAE⋅100 g-1, while AA varied from 110.5 ± 7.4 to 254.6 ± 5.4 μM Trolox⋅g-1 (ABTS) and 41.1 ± 1.4 to 117.2 ± 3.0 μM Trolox⋅g-1 (DPPH). Anthocyanin concentrations ranged from 77.6 ± 2.1 to 199.5 ± 1.32 mg C3G⋅100 g-1. Both solid:liquid ratio and ethanol concentration significantly influenced PCC and DPPH antioxidant activity. Higher phenolic content and DPPH activity were observed at solid:liquid ratios up to 1:10, likely due to enhanced mass transfer. Intermediate ethanol concentrations yielded the highest values, probably because of the varying polarities of phenolic compounds in blackberry pomace. Anthocyanin content was significantly affected only by ethanol concentration, with maximum recovery at 53% ethanol. All models showed good fit with low residual values, no significant lack of fit (p > 0.05), and satisfactory determination coefficients (R² > 0.7), except for ABTS. Optimal extraction conditions for maximizing phenolic content, anthocyanins, and antioxidant capacity were 53% ethanol concentration and a 1:13 solid:liquid ratio. These results underscore the importance of optimizing extraction parameters for the valorization of blackberry residues as natural agents for food applications.