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MEASUREMENT OF FLOW ABILITY OF BUTTER BY CAPILLARY RHEOMETRY
Author(s) -
SHUKLA A.,
RIZVI S.S.H.
Publication year - 1995
Publication title -
journal of texture studies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.593
H-Index - 54
eISSN - 1745-4603
pISSN - 0022-4901
DOI - 10.1111/j.1745-4603.1995.tb00967.x
Subject(s) - rheometry , capillary action , rheology , slippage , shear rate , apparent viscosity , shear (geology) , materials science , chemistry , composite material , viscosity , analytical chemistry (journal) , thermodynamics , mechanics , chromatography , physics
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.