Effect of Variety and Process Parameters on Physicochemical Properties, Phenolic Compounds and Antioxidant Properties of Grape Syrup

Grape juice, non-fermented products, which is prepared from the concentration of grape juice and has a high nutritional and medicinal value due to having a suitable amount of fast-digesting, monosaccharides, minerals, vitamins, organic acids and phenolic compounds, flavonoids. The type and percentage of its constituent compounds are affected by genotype and environmental conditions, as well as the conditions of production and concentration of grape juice also affects its quality characteristics. In this study, grape juice from two varieties of red Gazane and green Fakhri grape using different concentration methods including heating in atmospheric conditions and microwave, as well as, different concentrations of syrup soil (0.5 and 1%) with carbonate Calcium production and then the amounts of phenolic compounds, flavonoids, anthocyanins and antioxidant properties as well as physicochemical parameters (pH, acidity, total sugar and brix) and sensory were studied. The results of the present study showed that the highest phenolic, flavonoid, anthocyanin and free radical scavenging activity of DPPH was observed in red grape treatments and microwave heating method (p <0.05). Red grapes had higher pH, acidity, brix and total sugar values than green grapes and the use of microwave heating method had a positive effect on these characteristics compared to atmospheric heating method. The composition of syrup soil (1%) and calcium carbonate increased pH and decreased brix and acidity (p <0.05). Physicochemical properties of all produced syrup were within the permissible limits of the Iranian national standard. The highest sensory score was also observed in red grape+ microwave + syrup soil 0.5% and red grape+ microwave + syrup soil 1% + calcium carbonate Therefore, it seems that the produced grape syrup, while having suitable physicochemical properties, can be considered as a source of bioactive compounds with high antioxidant activity in food and pharmaceutical industries.