Improving carotenoid extraction, stability, and antioxidant activity from Citrus sinensis peels using green solvents

Carotenoids have a wide range of applications in the food, pharmaceutical, and cosmetic industries as natural coloring agents and antioxidants. Consequently, industries are more concerned about extracting them from natural resources and by-products. The present research aimed to evaluate the extraction efficiency of carotenoids from orange peels using hydrophobic deep eutectic solvents (HDESs) as alternatives for organic solvents. The antioxidant capacity and color stability of HDESs extracts were monitored for 20 days and to intensify the extraction process, ultrasound-assisted extraction (UAE) was optimized using a response surface methodology (RSM). Menthol:Eucalyptol (Me:Eu) extract showed the highest carotenoid extraction yield [359.3 +/- 3.5 mg/100 g of fresh weight (fw)], and also presented high stability during the storage period. HDESs extracts showed higher antioxidant capacity compared to hexane extracts, while Me:Eu extracts showed the lowest color variation (5.9 +/- 0.2). Optimal parameters using Me:Eu were extraction time of 20 min, ultrasonic power of 120 W (60%), and solid-liquid ratio of 1:20 (g/mL) reaching a carotenoid content of 573.4 mg/100 g(fw). While, C12:C8 optimal parameters were 10 min, 80 W (40%), and a solid-liquid ratio of 1:10 (g/mL), providing a carotenoid content of 183.7 mg/100 g(fw). To establish if the solvents used are greener alternatives, the EcoScale was used and showed that UAE is a sustainable method to recover carotenoids using HDESs. Overall, the results showed that HDESs can improve carotenoid stability, and when combined with the intrinsic safety and edibility of their components, it makes these extracts appealing for food industry.