Changes in the phenolic profile, antioxidant capacity and in vitro bioaccessibility of two Algerian grape varieties, Cardinal and Dabouki (Sabel), during the production of traditional sun-dried raisins and homemade jam

BACKGROUND: Excessive production of grape is valorized by traditional drying and homemade jam production in some regions of Algeria. OBJECTIVE: This study aims to investigate the changes in antioxidant activity, phenolic compounds and their bioaccessibility in two grape varieties (Cardinal and Dabouki or Sabel) as a result of traditional sun drying and homemade jam processes. METHODS: Fresh and dried grapes, as well as jam samples were subjected to a series of spectrophotometric analyses including total phenolics, flavonoids, and antioxidant activity. Individual phenolic compounds were identified and quantified by HPLC-DAD-MS-QTOF. An in vitro gastrointestinal digestion was applied to evaluate the bioaccessibility. RESULTS: Both traditional processes led to considerable losses in the levels of some phenolic compounds and their antioxidant activities. However, an increase in the content of other phenolic acids was also observed after processing. Total phenolics, total flavonoids and total antioxidant capacity recovery values of the dialysable fraction of processed samples were higher than those of fresh grapes for both varieties. CONCLUSIONS: Traditional raisins and homemade jams could be considered as good sources of natural antioxidants, although a modification of some critical steps that may negatively affect their antioxidant properties is suggested in the light of this study.