Effects of deproteinization on rheological properties of polysaccharides from Rosa acicularis ‘Lu He’ and Rosa acicularis Lindl fruits

Polysaccharides from the fruits of Rosa acicularis are one of the main functional components with superior biological activities and physicochemical properties. Rosa acicularis 'Lu He' is a new variety derived from the wild type Rosa acicularis Lindl. A comparative study was performed on the chemical composition and rheological properties of polysaccharides of rosehip from Rosa acicularis 'Lu He' (RLHP) and Rosa acicularis Lindl (RLDP) before and after deproteinization. The polysaccharide extracts, regardless of deproteinization, were acidic heteropolysaccharides composed of 48.3–51.6% carbohydrate and 29.2–43.2% uronic acid on dry weight basis and small amounts of protein (1.8–6.2%) and polyphenol (2.1–6.3%). Steady shear and frequency scanning measurements were used to evaluate the changes in concentration, temperature, pH and salts on the apparent viscosity and dynamic viscoelasticity of polysaccharide of rosehip solutions. The results showed that the apparent viscosity of RLHP was higher than that of RLDP at the same concentrations (2–6%), while apparent viscosity of RLHP and RLDP increased by 7.2% and 20.5% after deproteinization, respectively. Solutions of polysaccharide of rosehip exhibited shear-thinning behaviors, and higher concentrations caused more significant pseudoplastic effects. The solution properties changed from pseudoplasticity to plasticity when the initial apparent viscosity was below 7.5 mPa s. Thixotropy of polysaccharides of rosehips was stronger after protein removal; moreover, the polysaccharides before deproteinization (RLHP-1, RLDP-1) exhibited better gel properties than the deproteinized polysaccharides (RLHP-2, RLDP-2). This rheological property information will help proper product design to ensure the stability of food products enhanced with polysaccharides from rosehips.