Comparison of flavonoids, phenolic acids, and antioxidant activity of explosion-puffed and sun-dried jujubes (Ziziphus jujuba Mill.).

The goal of the present study was to investigate the effect of explosion puffing and sun-drying on individual phenolic acids in four forms (free, esters, glycosides, and insoluble-bound), flavonoids, total phenolic content (TPC), and their antioxidant activity on jujube samples. Phenolic compounds were identified and quantified using high-performance liquid chromatography. Antioxidant capacity of jujube samples was evaluated by 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity and total reducing power. The results showed that all samples significantly differed in their phenolic contents, phenolic acid and flavonoid composition, and antioxidant activities. The explosion-puffed jujubes had the highest total gallic, p-hydroxybenzoic, vanillic, p-coumaric, ferulic acids, and rutin contents. Also, explosion-puffed jujubes contained a higher level of total phenolics and antioxidant activity than their counterparts. Among phenolic acid fractions in four forms, each form of phenolic acids in explosion-puffed jujubes had the most abundant content, followed by fresh and sun-dried jujubes. The glycosided and insoluble-bound phenolic acid fractions for each sample represented the highest TPC and the strongest antioxidant activity. The results indicated explosion puffing was a good choice for jujube processing.