The effects of solution type temperature and time on antioxidant capacity of osmotically dried celery leaves

Abstract

Osmotic drying (OD) of celery leaves was studied in two osmotic solutions (ternary aqueous solution and sugar beet molasses), at three temperatures (20, 35 and 50?C), and diverse immersion periods (1, 3 and 5 h). The aim was to examine the influence of the used hypertonic agent, temperature and immersion time on antioxidant capacity (AOC) and colour characteristics of the samples. AOC of celery leaves was assessed by the spectrophotometric assays (ABTS, FRAP and DPPH), as well as two direct current polarographic assays, HPMC assay based on the decrease of anodic current of Hydroxo Perhydroxo Mercury (II) complex and MRAP assay based on the decrease of a cathodic current of Hg (II) reduction. Total phenolic content was determined by Folin-Ciocalteu assay. The Relative Antioxidant Capacity Index (RACI), calculated by assigning equal weight to all applied assays was used to achieve a more comprehensive comparison between analyzed samples, as well as applied assays. The obtained results indicated decreases in the AOC of celery leaves during the OT in ternary solution, while the AOC was increased in sugar beet molasses solution. According to RACI evaluation the most convenient process parameters were temperature of 35oC and immersion time of 5h.