Physicochemical and rheological properties of tangerine peel pectin extracted using organic acids with or without ultrasonication assistance

Abstract

This study was conducted to extract pectin from tangerine peel waste using organic acids (citric acid (CA) and oxalic acid (OA)) with or without ultrasonication assistance. The highest extraction yield of pectin was obtained in organic acid extraction (CA, 18.4%, OA, 17.8%). The moisture content of the dried pectin ranged from 8.1 to 9.9%. The highest equivalent weight, methoxy content (MeC), anhydrouronic acid content (AUA), and degree of esterification (DE) were recorded for HCl. The ultrasound-assisted extraction (UCA or UOA) of pectin showed the highest total phenol content (TPC) compared to other treatments. A structural analysis of extracted pectin revealed a broad absorption band between 3000 and 3700 cm^{− 1} corresponding to O–H stretching vibrations. The emulsions developed using each pectin indicated that a 1.0% concentration (12.6 0.73 to 22.2 1.78 μm) was more effective in producing the smallest droplet size compared to a 0.5% concentration (19.1 ± 0.92 to 29.4 ± 1.88 μm). However, storage studies indicated that 1.0% of HCl, CA, and UCA can stabilize emulsion during 14 days of storage at room temperature, except for OA or UOA. The developed emulsions exhibited viscoelastic behavior. Hence, CA-based pectin extraction with or without ultrasonication could be an eco-friendly alternative to the conventional extraction method.