Optimization and identification of non-extractable polyphenols in the dietary fiber of jackfruit (Artocarpus heterophyllus Lam.) pulp released by alkaline, acid and enzymatic hydrolysis: Content, composition and antioxidant activities

The study presented the first comparison of content and composition along with the antioxidant activities of non-extractable polyphenols (NEPP) in the dietary fiber of jackfruit pulp (JDF) released by alkaline, acid and enzymatic hydrolysis. Firstly, the NEPP extraction was optimized by response surface methodology (RSM), and the alkaline hydrolysis extract contained the most abundant content. Besides, the composition of extracts were characterized by UPLC-ESI-QTOF-MS/MS and the alkaline hydrolysis extract possessed most diverse NEPP (4 phenolic acids and 13 flavonoids). Moreover, the antioxidant activities of NEPP were tested by ABTS·+, ORAC and PSC scavenging ability assays, the antioxidant activities of alkaline hydrolysis extract were significantly highest among three extracts. This study provided available evidence for the NEPP released from dietary fiber (DF) by different methods, and revealed alkaline hydrolysis extract promising potential as a natural source of health care products.