Investigation the Rheological and Antioxidant Properties of Pomegranate (Punica granatum (L.) cv. Rabab) Juice Concentrate

Owing to presence of large amounts of antioxidants, pomegranate (Punica granatum L.) reveals great nutritional properties. Study on rheological properties of fruit juice concentrates in order to appropriate design of manufacturing processes and to determine the nutritional values is of importance. The objectives of this study were investigating the effects of different total soluble solids (55, 60, and 65 °Brix) and temperatures (5, 15, and 25 °C) on rheological properties of fresh pomegranate juice concentrate as well as on antioxidant and rheological properties during 20-week storage. The concentrated pomegranate juice samples were stored at different temperatures namely -80 (control), -20, 4, 20, and 35 °C for measuring their rheological and antioxidant properties. Although, the viscosity of fresh pomegranate juice concentrate (particularly at 65 °Brix performed at 5 °C) decreased by increasing the shear rate and exhibited a typical non-Newtonian shear thinning behaviour (fitted to Herschel-Bulkley model), its storage led to shear thickening behaviour. After 20 weeks storage at different temperatures, FRAP value decreased and IC50 one increased; however, FIC and CUPRAC values remained constant. The samples stored at 4°C for 14 weeks revealed similar rheological (viscosity and shear stress) and antioxidant properties to those stored at -20 °C. Taking into account the minimum cost, the best storage to yield high quality product was 4°C.