Recovery of anthocyanins from black currant (Ribes nigrum L.) and evaluation of their bioactive properties

This thesis aims to recover anthocyanins from black currants using three different extraction methods. Conventional solvent extraction was compared with bath-type and probe-type ultrasound-assisted extraction methods under various temperature and duration conditions. Ethanol (50%) and ethanol acidified with citric acid (0.01% w/v) were used as solvents in the extractions. The total monomeric anthocyanin content, total phenolic content, total flavonoid content, and antioxidant activity of black currants and the obtained extracts were determined, and the anthocyanin profile was identified using HPLC. The total monomeric anthocyanin content of black currants was determined as 764.00 ± 4.83 mg cyanidin-3-rutinoside/kg, total phenolic content as 4421.46 ± 83.56 mg gallic acid/kg, total flavonoid content as 902,12 ± 7,12 mg catechin/kg, and total antioxidant activity as 24.93 ± 0.29 mM. The main anthocyanins in black currants were identified as delphinidin-3-rutinoside (54.07%), cyanidin-3-rutinoside (26.39%), delphinidin-3-glucoside (15.92%), and cyanidin-3-glucoside (3.62%), respectively. Conventional extraction performed for 24 hours at 40 °C with a 1:10 (g/g) solid-to-solvent ratio, bath-type ultrasound-assisted extraction for 15 minutes at 40 °C with the same ratio, and probe-type ultrasound-assisted extraction for 5 minutes at 40 °C with the same ratio resulted in total phenolic content levels of 6200 mg gallic acid/kg. When probe-type ultrasound-assisted extraction was performed for 5 minutes at 40 °C with a 1:20 (g/g) solid-to-solvent ratio using acidified ethanol instead of ethanol as the solvent, the total flavonoid content of the extracts increased by 13.69%. In probe-type ultrasound-assisted extraction, the optimal conditions for recovering monomeric anthocyanins using ethanol as the solvent were determined as 5 minutes at 25°C with a 1:20 (g/g) solid-to-solvent ratio. When using acidified ethanol, the optimal temperature conditions were found to be 10 minutes at 25°C with a 1:20 (g/g) solid-to-solvent ratio. In both bath-type and probe-type ultrasound-assisted extraction methods, the use of acidified ethanol resulted in lower polymeric color percentages and increased anthocyanin stability. The total antioxidant activity of black currants was determined as 42.54 ± 1.65 mM for conventional extraction, 45.18 ± 0.13 mM for bath-type ultrasound-assisted extraction, and 49.08 ± 0.99 mM for probe-type ultrasound-assisted extraction. The antioxidant activity values of extracts obtained using ultrasound-assisted methods were higher than those of conventional extraction. The highest increase in anthocyanin components was achieved with probe-type ultrasound-assisted extraction using ethanol under the conditions of 5 minutes at 40°C with a 1:20 (g/g) solid-to-solvent ratio. The findings indicate that ultrasound-assisted extraction methods are more efficient in terms of bioactive compounds compared to conventional extraction and that these methods are more suitable for recovering anthocyanins from black currants. The extracts obtained from black currants are considered to have potential applications as natural colorants in the food, chemical, pharmaceutical, and textile industries and could also be evaluated as antioxidant sources in the design of new functional food products.