Abstract:

In this study, apple pectins (APs) were extracted from apple peel by ultrasound-assisted extraction with citric
acid, and investigated for physico-chemical properties. Under the optimized conditions of pH 2.5 citric acid solution as the
extraction solvent, 450 W ultrasound power and 30 min radiation time, the yield of APs was 14.6%. The extracted APs were
characterized by a degree of esterification of 69.9% and a molecular weight larger than 400 kD, and contained 92.8% total
sugar, 58.5% aldonic acid. GC data indicated that the APs consisted of eight monosaccharides including Rha, Fuc, Ara, Xyl,
Glc, Gal, GlcA and GalA, with a relative molar ratio of 9.5:19.2:4.7:0.1:4.6:3.6:2.3:56.3 and a significantly high percentage
of Fuc, reaching 19.2%. Further results revealed that the extraction of Fuc-rich APs was likely associated with the method
using citric acid as the extraction solvent.

Key words: apple pectin, extraction, fucose, physico-chemical properties, citric acid