Effect of concentration temperature on some bioactive compounds and antioxidant proprieties of date syrup

Abstract

The effect of the concentration temperature on the antioxidant activity, carotenoid and phenolic compounds of date syrup was investigated. Date juice was concentrated at 100 ℃ and at “60 ℃ in vacuum”. After concentration, total phenolic, tannin, non-tannin, flavonoid and carotenoid content were determined spectrophotometrically and high-performance liquid chromatography was used for determination of 5-Hydroxymethyl-2-furfuraldehyde content. The antioxidant activity of date syrup was evaluated by various antioxidant methods including total antioxidant, 2,2-diphenyl-1-picrylhydrazyl free radical scavenging test, ferric reducing antioxidant power and β-carotene bleaching. All date syrups showed strong antioxidant activity accompanied by high total phenolic contents. Results showed that concentration at 100 ℃ significantly enhanced the antioxidant activities and total phenolic contents of date syrups compared to vacuum concentration at 60 ℃. A good correlation between the antioxidant activity and total phenolic content and flavonoid was observed.