Modeling the Time-Dependent Rheological Properties of Pistachio Butter
الموضوعات :Seyed M. A. Razavi 1 , Masoud Taghizadeh 2 , A Shaker Ardekani 3
1 - Department of Food Science and Technology, Ferdowsi University Mashhad (FUM),Mashhad PO Box: 91775-1163, Iran
2 - Department of Food Science and Technology, Ferdowsi University Mashhad (FUM),Mashhad PO Box: 91775-1163, Iran
3 - Pistachio Research Institute (PRI), Rafsanjan PO Box: 77175-435, Iran
الکلمات المفتاحية: pistachio butter, rheology, thixotropy, modeling, weltman model, shear stress decay model,
ملخص المقالة :
Pistachio butter (semi solid paste), which is made from roasted pistachio kernels, is an appropriate alternative to work on because of its high nutritional and economical values. In this study, timedependent flow properties of pistachio butter were determined at two different temperatures (25˚C and 45˚C) for five different formulations (with different levels of emulsifying agents). Forward and backward flow curves were plotted and the amount of existing hysteresis loop was measured. Also, shear stress vs. time of shearing data were assessed using three models namely; Weltman, First-order shear stress decay with a zero equilibrium stress value, and First-order shear stress decay with a nonzero equilibrium stress value. To evaluate the ability of these models to predict the rheological characteristics of pistachio butter, three statistical parameters namely; R2 , RMSE, and MRDM were used and finally the Weltman model was found to be the most appropriate to fit the experimental data. The results showed that pistachio butter exhibits a thixotropic behavior and its apparent viscosity decreases with increasing the time of shearing.
