The effect of boiling on qualitative properties of grape juice produced by the traditional method

摘要

In this study, grape molasses produced by using the traditional methods from the from Taşkent town of Konya were analysed for their some quality values. Depending on the type of grape molasses and boiling periods, some differences were found in physico-chemical properties. Protein, pH, total acid, hydroximetil furfural, soluble dry matter, total phenol and viscosity values were found between 0.260 % and 0.421 %, 7.82 and 8.35 %, 0.477 % and 0.585 %, 3.312 mg/kg and 6.336 mg/kg, 20.447 mg/L and 25.813 mg/L, 61.5 and 67.0 % and 65.60 mPa.s to 91.75 mPa.s, respectively. Antioxidant activity values were determined between % 86.437 and % 93.395. L* values were established between 20.41 and 55.29, while a* values are found between 8.11 and 18.69 and b* values are between 34.94 and 47.47. The K, Mg, Na, P, Ca contents of all the molasses samples has been detected at high levels. At some quality parameters such as protein, total acid and L* values have been decreased towards to end of the boiling period. As a result, antioxidant activity and anthocyanin in the red grape molasses were superior to compared with other types of grape molasses.