Natural deep eutectic solvents extraction of anthocyanins – effective method for valorisation of black raspberry (Rubus occidentalis L.) pomace
Nemanja Krgović, Miloš Jovanović, Snežana Kuzmanović Nedeljković, Katarina Šavikin, Nataša Jovanović Lješković, Milan Ilić, Jelena Živković, Nebojŝa Menković
Abstract
This study aimed to establish NaDES-based ultrasound-assisted extraction as a novel, sustainable, and ecologically suitable method for valorisation of black raspberry pomace remaining after juice production. Accordingly, a range of NaDESs, composed of hydrogen bond donor choline chloride and different hydrogen bond acceptors were screened to select the most appropriate for cyanidin-3- O -rutinoside and total anthocyanins extraction from black raspberry pomace, and to compare with conventional solvents. In addition, the impact of hydroxypropyl- β -cyclodextrin (HP- β -CD) on anthocyanins extraction capacity of NaDES and water was evaluated, as well as the influence of NaDES on anthocyanins storage stability at 4, 25 and 40°C. On the basis of cyanidin-3- O -rutinoside and total anthocyanin content (TAC), along with antioxidant activity, citric acid/choline chloride NaDES was selected for extraction conditions optimization by Box-Behnken design coupled with response surface methodology. The optimal conditions were found to be an extraction time of 52.9 min, a temperature of 65°C, and 15.6 % ( w/w ) water in NaDES, resulting in maximized extraction yields of target compounds, cyanidin-3- O -rutinoside (7.60 mg/g DW) and TAC (6.88 mg CGE/g DW). By incorporating different concentrations of HP- β -CD (1.5, 3 and 6 % w/w ) in citric acid/choline chloride NaDES, downward trend was observed, while in the case of water anthocyanins extraction was improved. A 30-day stability study revealed that NaDES provided the best anthocyanins preservation at a defined temperature range compared to extracts prepared with water, 70 % ethanol and 70 % methanol. Black raspberry pomace is a promising raw material rich in anthocyanins that can be used in green technology-oriented industries. • Black raspberry pomace is a promising raw material rich in anthocyanins. • Natural deep eutectic solvents enable green and effective extraction of bioactives. • Choline chloride/citric acid proved to be the most appropriate extraction solvent. • Cyclodextrins incorporation decreased extraction yield of anthocyanins. • Selected eutectic solvent provided the best anthocyanins stability during storage.