Structure and physicochemical properties of pectin from date fruits (Phoenix dactylifera L.)

In this study, we investigated the chemical structure of pectin from three date fruit cultivars (Barhi, Shishi, and Neghal) of varying hardness. Date fruit pectin is amorphous, relatively rigid at moderate temperatures, and less chemically stable at high temperatures. It possesses moderate molecular weight (31.5–39.3 kDa) and shear-thinning behavior. The soluble pectin is primarily composed of highly methoxylated (57–72.1%) and moderately acetylated (21–32.2%) homogalacturonan (HG) with a small content of rhamnogalacturonan-I (RG-I) and traces of xylo- and gluco-galacturonan. RG-I contains branched arabinan and arabinogalactan-I (AG-I) side chains composed of terminal, →3)-, →5)- and →3,5)-linked α-L-arabinofuranosyl residues and a β-ᴅ- galactopyranosyl domain with →3)-, →6)- and →3,6)-linked Galp acting as branch points for Araf substituents. The higher degrees of methyl esterification in Barhi pectin are associated with softness of the fruit. These results provide new insights into pectin in the primary cell walls of palm fruits.