An Acid-Free Alternative to Pectin Production from the Cell Walls of Olive Oil Waste and Different Fruits Using Choline Chloride

The pectin from the cell walls of olive waste (alperujo) and apple, orange and strawberry fruits was extracted using choline chloride (ChCl) and the yield and chemical and structural compositions were compared to pectin extracted using citric acid (CA) and ammonium oxalate/oxalic acid (AOOA). According to the results, the alperujo pectin extracted using ChCl from alcohol-insoluble residue (AIR) showed a higher yield (2.20-2.88% on the basis of dry weight of AIR) than using CA (0.65-1.22%) but lower than using AOOA (3.92-5.42%). For fruit pectin, the highest yield was obtained using CA (8.81-16%), followed by AOOA (5.4-6.63%), although for apple pectin, ChCl gave a similar yield (5.36%) to AOOA. The uronic acid contents in all ChCl pectins (45.9-70.6% dry basis AIR) were higher or similar to that of the other extracting agents (30.6-65.2%), although a lower level of neutral sugar side chains was detected, with a lower degree of branching and degree of methylation. The NMR and FT-IR spectroscopy of the pectin isolated using ChCl confirmed its slightly different structural composition with respect to CA and AOOA pectin. Therefore, depending on the source material and functionality, pectin isolated using ChCl could be an acid-free alternative to pectin production.

Automated summary

Pectin from olive waste and various fruits was extracted using choline chloride (ChCl) and compared to pectin extracted using citric acid (CA) and ammonium oxalate/oxalic acid (AOOA). The yield and chemical and structural compositions were analyzed. The results showed that ChCl extracted pectin from olive waste had a higher yield compared to CA but lower compared to AOOA. For fruit pectin, the highest yield was obtained using CA, followed by AOOA. The uronic acid contents were higher in ChCl pectins, but they had lower levels of neutral sugar side chains. NMR and FT-IR spectroscopy confirmed the slightly different structural composition of ChCl pectin compared to CA and AOOA pectin. Depending on the source material and functionality, ChCl-extracted pectin could be an acid-free alternative for pectin production.