Effect of ultrafiltration process on physico-chemical, rheological, microstructure and thermal properties of syrups from male and female date palm saps. (15th July 2016) - Makhlouf-Gafsi, Ines
Highlights: Syrups were prepared using vacuum concentration of date palm sap at 60 °C. Ultrafiltration affects physico-chemical, rheological and thermal properties. The microstructure of sap syrups is also affected by ultrafiltration process. Syrups stability is provided by evaluating area between heating and cooling curves. Abstract: This study investigates the effect of the ultrafiltration process on physicochemical, rheological, microstructure and thermal properties of syrups from male and female date palm sap. All the studied syrups switched from pseudoplastic rheological behaviour ( n = 0.783) to Newtonian behaviour ( n ∼ 1) from 10 to 50 °C respectively and present similar thermal profiles. Results revealed that the ultrafiltration process significantly affects the rheological behaviour of the male and female syrups. These differences on rheological properties are attributed to the variation of chemical composition between sap and sap permeate syrups. Furthermore, the effect of temperature on viscosity of the syrups was investigated during heating and cooling processes at the same shear rate (50 s −1 ). This study provides idea of the stability of the syrup by evaluating the area between heating and cooling curves. Actually, the syrup prepared from male sap permeate is the most stable between the four studied syrups.