Efeito da extração com Solventes Eutéticos Profundos associada a Radiação Gama na estabilidade de antocianinas de maçã

Abstract

The apple epicarp is a valuable source of phytochemicals, especially polyphenols, which are more concentrated in this part of the fruit. Anthocyanins are an example of these compounds, which are responsible for the red color, characteristic of apples.These compounds can be extracted with Deep Eutectic Solvents - DES, which are biodegradable and have great extraction potential. Therefore, the objective of this work was to evaluate the extraction with deep eutectic solvents and the effect of gamma radiation on the stability of apple anthocyanins. Initially, the extraction of anthocyanins from the fresh epicarp of Fuji Suprema apples was performed using seven solvents, namely: Ethanol 70% acidified with HCl (1%); Methanol 70% acidified with HCl (1%); DES 1 composed of Choline Chloride (ChCl) and propylene glycol; DES 2 composed of ChCl and tartaric acid; DES 3 composed of ChCl and citric acid; DES 4 composed of ChCl and malic acid and DES 5 composed of ChCl and glycerol. Among these, the three solvents with the best anthocyanin extraction were exposed to gamma radiation at doses of 0.5 and 1.0kGy. A sample of the epicarp was irradiated at the doses mentioned above, for later extraction with the same solvents. Then, the stability of the extracts was analyzed, against light and temperature (60oC, 70oC, 80oC and 90oC) in relation to the content of total monomeric anthocyanins, by the differential pH method and by HPLC. The antioxidant activity by DPPH and the content of total phenolic compounds were analyzed. The best anthocyanin extractor solvents were: Ethanol 70% acidified (1%) with HCl (20.55 mg of cyanidin-3-glycoside/g dry mass); DES 1 composed of ChCl and propylene glycol (20.82 mg of cyanidin-3-glycoside/g dry mass) and DES 2 composed of ChCl and tartaric acid (22.22 mg of cyanidin-3-glycoside/g dry mass). The irradiated extracts had a higher Total Monomeric Anthocyanin - AMT content (up to 14% more) than the non-irradiated ones. In the kinetics of degradation, a significant reduction in the anthocyanin content was obtained in the initial 30 min, and this occurred in all extracts analyzed, regardless of radiation dose or solvent. At temperatures of 80°C and 90°C anthocyanins were close to being completely degraded. The extracts made with the irradiated epicarp showed to be more stable to degradation against temperature (60oC and 70oC) and light. Exposure to light and temperature decreased Total Phenolic Compounds and antioxidant activity by the DPPH method. The extraction with DES, as well as the application of radiation, showed to be promising in the extraction of anthocyanins from the epicarp of the apple, showing potential for use in the industry.