Extraction optimization and nanoencapsulation of jujube pulp and seed for enhancing antioxidant activity

• The extraction conditions of jujube pulp and seed were optimized, respectively.
• This potent antioxidant activity correlated well with the total phenolic compounds.
• The jujube seed extract showed stronger antioxidant activity than the pulp extract.
• The jujube pulp and seed extract-loaded chitosan nanoparticles were prepared, respectively.
• The stabilities of jujube pulp and seed extract were effectively enhanced by nanoencapsulation.

The aim of this study was to optimize extraction conditions for jujube pulp and seed in order to obtain maximum active ingredient yield and antioxidant activity, as well as to prepare chitosan nanoparticles loaded with jujube pulp and seed extracts for enhancing stability. The extraction conditions, i.e. temperature, time, and ethanol concentration, were optimized at the following respective values: 61.2 °C, 38 h, and 60.4% for pulp, and 58 °C, 34 h, and 59.2% for seed. The jujube nanoparticle size significantly increased with a higher chitosan/sodium tripolyphosphate ratio and extract concentration. Entrapment efficiency was greater than 80% regardless of preparation conditions. The stabilities of jujube pulp and seed extract in terms of total phenolic content and antioxidant activity were effectively enhanced by nanoencapsulation. In conclusion, jujube pulp and seed extracts prepared using optimal conditions could be useful as a natural functional food ingredient with antioxidant activity, and nanoencapsulation can be used to improve the stability of jujube extract. Therefore, these results could be used to promote the utilization of not only jujube pulp but also seed, by product.

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