Abstract
The food industry generates a huge amount of waste from the production of food and processed products. There is a need to find a different outcome for this waste, use or reuse, to minimize this problem. Regarding citrus fruits, the waste of this cultivar has a significant amount of bioactive compounds, such as ascorbic acid (AA). The extraction of these compounds can also contribute to environmental pollution due to energy usage and polluting organic solvent by-products. Nonconventional extraction techniques and less-polluting solvents to recover these compounds from citrus waste would be a better and less-polluting choice. In this study, six hydrophilic natural deep eutectic solvents (NADESs) were prepared to extract AA from orange peel (navel cultivar). EtOH 50% was used as the control. The extraction was performed with the aid of ultrasound-assisted extraction (UAE). The following optimized UAE parameters were used: extraction time (5, 10, and, 15 min), intensity (100 W, 200 W, and 400 W), and a magnetic stirring time after UAE (0, 20, 30, and 45 min). The determination of AA was made by HPLC-UV/VIS. Mobile phase A included Milli-Q water/formic acid (95:5), while mobile phase B included acetonitrile/A (60:40). An injection volume of 1 µL and a flow rate of 0.5 mL/min were used. A standard calibration curve was constructed using the same conditions as the samples (R = 0.9998). The selected optimal conditions were 10 min of extraction, 100 W of intensity (no statistical differences found among intensities), and 45 min of magnetic stirring after treatment. The NADES that presented the highest extraction yield was malic acid with glucose (11.76 mg/100 mL) followed by L-proline with malic acid (7.44 mg/100 mL). NADEs provided higher extraction yields than did EtOH 50% (5.41 mg/100 mL). In conclusion, two of the studied NADESs extracted more AA from orange peel than did EtOH 50%.
Supplementary Materials
The presentation material of this work is available online at https://www.mdpi.com/article/10.3390/Foods2022-12976/s1.
Author Contributions
C.G.-U., investigation, formal analysis, and writing—original draft; I.M., formal analysis; J.B., writing—reviewing and editing, and conceptualization; D.L.-M., writing—reviewing and editing and data curation; M.J.E., conceptualization, supervision, funding acquisition, and project administration; A.F., writing—reviewing and methodology. All authors have read and agreed to the published version of the manuscript.
Funding
This work was financially supported by the Ministry of Science and Innovation (Spain) StateResearch Agency (PID-2019-111331RB-I00/AEI/10.13039/501100011033).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
Agricultural Cooperative Sant Bernat from Carlet, Spain, donated the raw materials.
Conflicts of Interest
The authors declare no conflict of interest.
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