Abstract

The rheological properties of four kinds of jams (Kewpie strawberry, Marmalade, Blueberry and ST. Dalfour) were determined by the rheometer of MCR101. It showed that all the jam samples belonged to non-Newtonian fluid model, with thixotropy and pseudoplastic. Three jams were fit for Herschel-Bulkley model, although yield stress existed in the samples at 25°C and was calculated as 25.07, 99.13 and 103.67 Pa for ST. Dalfour, Kewpie strawberry and Blueberry, respectively. More so, three jams were fit for Arrhenius model, and the flow activation energies were 13.79, 15.10 and 21.46 kJ/mol for Blueberry, ST. Dalfour and Kewpie strawberry, respectively. The oscillatory test data were revealed due to the increase in frequency, storage modules (G′) and loss modules (G″), the decrease in viscosity (η) and the exhibition of shear thinning behavior by the jams. The G′, G″ and η of Blueberry were the highest, while those of ST. Dalfour were the lowest. According to the time dependent behavior, it was revealed that Kewpie strawberry had the most instability and ST. Dalfour had the most stability, which may be related to the flow activation energy. However, by the sensory properties, the lowest of the overall acceptability was Marmalade sample.

Key words: Jams, rheological properties, viscosity, storage modulus G′, loss modulus G’.