Phenolic compounds as antioxidants of some products manufactured from two cultivated Egyptian varieties of seedless grapes

摘要

Two varieties namely Early superior and Flame seedless grapes were analyzed qualitatively and quantitatively to evaluate the antioxidant compounds such as phenolic compounds and activities of antioxidants for the two varieties. Also prepared juices, jam and raisins were also undertaken. Results showed that there is a little significant difference for chemical constituents between the two investigated varieties except for total soluble solids which was higher in Flame seedless grape than Early superior grape. Flame seedless juices had the highest content of total phenolics and flavonoids which was 67.25 and 30.40 mg/100 ml while, flame seedless raisins had the highest content of total phenolics and flavonoids which were 100.42 and 57.07 mg/100 g. Onthe other hand the highest content of total phenolics and flavonoids showed in Flame seedless variety jam which was 120.94 and 80.43 mg/100 g in Flame seedless jam, and it was 83.23 and 43.10 mg/ 100 g for jams Early superior. The highest content of total phenolics caused to rise the activity of total antioxidant was showed in Flame seedless raisins (83.37%). Results also indicated that the Flame seedless variety had the highest content of both catechin and p.coumaric which was 15.66 and 27.74 ng/100 gbut the lowest content was for caffeic and syringic 0.30 and 0.43 ug/100 g, respectively. On the other side, the lower content of phenolic compounds was noticed in Early superior grapes compared to Flame seedless variety. Sensory evaluation revealed thatno significant differences in color for jams and raisins prepared form the two tested varieties. The taste of early superior juice recorded the highest score than Flame seedless juice.