Microwave-assisted extraction of jujube polysaccharide: Optimization, purification and functional characterization

• Microwave-assisted extraction for Zizyphus jujuba Mill polysaccharide was built.
• Microwave power, water/raw material, time and temperature were optimized by RSM.
• A high emulsifying activity and stability was found for the purified polysaccharides.
• Jujube polysaccharide can be a novel natural antioxidant in functional foods.

The operational parameters involved in microwave-assisted extraction (MAE) of jujube polysaccharide including microwave power, water to raw material ratio and extraction temperature and time were optimized by RSM. MAE at 400 W, 75 °C, 60 min, using 30 g water/g powdered jujube was the best condition for maximum yield (9.02%) of polysaccharide. Two novel water-soluble polysaccharides (JCP-1 and JCP-2) with average molecular weights of 9.1 × 104–1.5 × 105 Da in term of the symmetrical narrow peaks were identified using the analytical purification procedures. The JCP-1 and JCP-2 mainly composed of glucose, arabinose, galactose and rhamnose in molar ratios of 1.4:2.1:4.2:0.9 and 1.2:1.8:4.1:1.1, respectively. The use of 1.5% JCP-1 led to a high emulsifying stability (95.5%) in a model oil-in-water type emulsion with a reduced surface tension (44.1 m N/m) and droplet size (1.32 μm), and an increased apparent viscosity (0.13 Pa s) during 21-day cold storage. The antioxidant activities were increased in dose-dependent manners (25–200 μg/mL).