Physicochemical characteristics and digestive properties of cell wall polysaccharides fractionated from sunflower meal

Summary To further utilise plant protein in oilseeds, it is vital to understand the structural and digestive characteristics of cell wall polysaccharides fractionated from sunflower meal. Water, chelator (cyclohexane‐trans‐1,2‐diaminetetra‐acetate, CDTA), sodium carbonate, 1 mol L −1 KOH, and 4 mol L −1 KOH were used to sequentially extract polysaccharides from sunflower meal, yielding samples that were labelled WSP, CSP, NSP, KS1, and KS4, respectively. Results indicated that galactose (1,6‐β‐D‐Galp) was the major sugar unit in WSP, while arabinose (1,3‐α‐L‐Araf and 1,5‐α‐L‐Araf) was the major sugar in the other four fractions. KS4 showed the highest molecular weight and the lowest thermal stability. The surface of the five polysaccharides was shown to be heterogeneous using SEM and AFM, with KS4 having the highest average size. The molecular weight of the five polysaccharides decreased during simulated digestion in vitro . It was noteworthy that the structures of KS1 and KS4 were harder to destroy than the other three fractions. These two polysaccharides are perhaps what makes sunflower protein difficult to digest, thereby decreasing its nutritional value.