Comparative studies of hydrocolloid pectin extracts from the pericarps and mesocarps of fresh and dried doum palm (Hyphaene thebaica) fruits

Abstract

Pectin, an amphipathic polysaccharide, which is inherently found in plants, has gained tremendous research interest in the development of novel biomaterials for applications in the food and pharmaceutical systems. Consequently, this research study aimed to extract and assess the characteristics of pectin from fresh and dried Hyphaene thebaica fruits. Pectin was extracted from the
pericarps and mesocarps of fresh and dried H. thebaica fruits using ammonium oxalate solution and a deep eutectic mixture made up of 10% choline chloride and ethylene glycol (1:2). The results revealed that the lyophilic H. thebaica fruit pectin extracts, exhibited thixotropic character and were unstable in alkaline medium with physicochemical properties; yield (18.49±0.65-28.11±1.33 %), moisture content (1.34±0.03-2.36±0.21 %), ash content (1.12±0.07-2.14±0.06 %), bulk density (0.04±0.02-0.18±0.05 gcm^-3) and pH of point zero charge (4.2±0.4-6.4±0.2). The chemical components; methoxyl content (6.58-8.83 %), anhydrouronic acid content (60.99-69.11 %) and degree of esterification (60.93-84.22 %) of the anionic polysaccharides were consistent with their intrinsic viscosities (1.23-2.14 cm³g^-1),
equivalent weights (549.91-883.19 gmol-1) and viscosity average molecular weights (675.0835 1024.5369 gmol^-1). Fresh mesocarp pectin extracted with ammonium oxalate (FMAMO) and dried pericarp pectin extracted with deep eutectic mixture (DPCCE) showed maximum and minimum swelling behaviors respectively. Dried pericarp pectin extracted with ammonium oxalate (DPAMO)
and fresh mesocarp pectin extracted with deep eutectic mixture (FMCCE) presented as slow and rapid set-gel pectins. FMCCE and DPAMO pectin extracts demonstrated the lowest and highest syneresis in protein stabilization respectively. The dried H. thebaica hydrocolloid pectin extracts were more sensitive to calcium. The fresh H. thebaica pectin extracts showed lower retrogradation tendency. This study did provide insights on the physicochemical properties of pectin implicit in H. thebaica fruit and presented the fruit as an alternative source of food and pharmaceutical grade pectin.