Effect of different thermal treatments and freezing on the antioxidant constituents and activity of two Bahraini date cultivars (Phoenix dactylifera L.)

Effect of several thermal treatments and freezing on the antioxidant properties of fresh dates of two cultivars (namely Khalas and Khunaizi) was investigated. Levels of phenolics, total flavonoids and anthocyanins were estimated. Antioxidant activity was measured by ferric reducing ability of plasma (FRAP), diphenylpicrylhydrazyl (DPPH) and deoxyribose assays. Results indicate differential effects of the treatments on the phenolic constituents. Generally, mild treatments and freezing significantly increased the level of total phenolics in both cultivars by 80180%. All treatments increased in the level of free phenolics in Khalas (between 10% and 540%). In khunaizi, the level of bound phenolic increased in all treatments (9250%). The level of total flavonoids increased by almost all treatments in both cultivars (33500%). Most treatments increased the FRAP value in khalas (up to 80%). Significant differences were noticed among the various treatments with regard to DPPH and OH radicals quenching capacities. Results may find applications in food science, food technology and nutrition.