**4. Conclusions**

After studying the different options available for pectin extraction, some key findings were made. First, it is crucial to remove essential oils and bioactive compounds beforehand, as they can interfere with the yield and quality of pectin. Citrus essential oil is most commonly removed by steam distillation. However, hydrodistillation and Solid–Liquid Extraction have been shown as an alternative. One advantage of hydrodistillation is that it can also partially extract pectin while the essential oil is retrieved, thus reducing time and resources. Pectin is mainly obtained through acid hydrolysis using different solvents. Hydrochloric acid and citric acid have shown better yields than other solvents, and both result in the obtention of highmethoxyl pectin with rapid jellification. However, when considering an industrial approach, the environmental and safety hazards should be revised; because of this, citric acid represents a better option. It is essential to perform a careful separation and purification of pectin with ethanol and acetone to achieve the appropriate organoleptic properties of citrus pectin. Finally, when considering a biorefinery approach, other valorization alternatives such as the recuperation of flavonoids, the use of sugar-rich hydrolysates to produce ethanol, organic acids, and cellulose, the anaerobic digestion to produce biogas and liquid digestate, and the possibility to use citrus residues directly as fertilizers, are presented as novel possibilities to improve the pectin production process under the biorefinery concept.

## **Acknowledgements**

Part of this research was financed by The Sustainable Development Goals (SDG) Center for Latin America and the Caribbean, based at Universidad de Los Andes (Bogotá, Colombia), in relationship with the call for the financing of teaching and research projects related to the scope of the sustainable development goals. Also, this research was also financed by the Product and Processs Design Group (PPDG) and the Research Vice-Chancellor Office of Universidad de Los Andes.

## **Conflict of interest**

The authors declare no conflict of interest.

*Pectins - The New-Old Polysaccharides*
