Measurement of Flow Ability of Butter by Capillary Rheometry

Abstract

Capillary rheometry was used to study and compare the rheological behavior of butters made from supercritically fractionated high melting triglyceride (HMT) and anhydrous milk fat (AMF) at different temperatures. Application of shear rates in the range of 17.37 to 346.93 S−1 showed a strong dependency of flow behavior on the capillary diameter, indicating slippage at the walls. Shear rates were corrected for wall‐slippage using capillaries with different diameters but the same length, and for non‐Newtonian behavior using the Rabinowitsch procedure. Shear stresses were corrected for entrance effect using capillaries of the same diameter but different lengths. Power law consistency indices (K), determined from loglog plots of corrected shear stresses versus shear rates, were found to have a negative correlation with temperature. Higher K values were observed for HMT butter depicting its more solid‐like behavior due to greater concentration of high melting triglycerides. A slight increase in the K values was observed on storage probably due to rearrangement of fat crystals and formation of secondary bonds between them. Flow indices were found to be relatively insensitive to both time and temperature of storage. From the flow curves (apparent viscosity versus shear rates), master curves were generated using the time‐temperature superposition principle.

Evaluation of Enzymatically Modified Soy Protein Isolate Film Forming Solution and Film at Different Manufacturing Conditions

“…The values of consistency index (k) and flow behavior (n) are determined as the intercept and slope of the log‐log plot of shear rate versus shear stress respectively (Shukla & Rizvi, ) (see b and d). Consistency index of the SPI solution determined the effectiveness of enzymatic incubation time and efficiency of transglutaminase on the inter‐ and intramolecular crosslinking of the protein solution (Ando et al., ).…”

Wall slip determination for coarse food suspensions in tube flow at high temperatures

“…In studies of flow behavior of food suspensions, most of which contained fine particles, slip at the wall has been frequently reported (Halliday & Smith, 1995;Qiu & Rao, 1989, 1990Shukla & Rizvi, 1995). While more insight on the flow behavior of coarse food suspensions is very much needed for the design of aseptic processing of particulate foods, due to the larger particle size, the choices of applicable viscometers are limited and information regarding wall slippage for such food suspensions is very scarce.…”

Rheology of mozzarella cheese: Extrusion and rolling

“…Several authors have also used the capillary rheometer to characterize viscoelastic food materials such as dough (Bagley, Dintzis, & Chakrabarti, 1998;Sharma, Hanna, & Chen, 1993;Shukla & Rizvi, 1995) and chocolate (Chen & Mackley, 2006;Ovaici, Mackley, McKinley, & Crook, 1998), due to their similarities to molten polymer. These authors suggest that the end effects in extrusion, which are associated with the excess pressure drop due to the die entrance and the exit flow of the material, are significant and should always be considered when determining the true rheological properties from capillary extrusion experiments.…”