RHEOLOGICAL PROPERTIES OF BLENDS OF SATURATED GLYCERIDES AND LIQUID SOYBEAN OIL

Abstract . Rheological behaviour of model blends (shortenings) prepared from liquid soybean oil, completely hardened cottonseed oil and glycerol monostearate was evaluated using the coaxial cylinders or the plate and cone system of the Rotovisko Viscometer. Initial and residual yield points, plastic (Bingham) viscosities, shapes and areas of hysteresis loops, and rates of recovery during rest and after shear were determined. There was almost linear intercorrelation between the yield points and the other rheological parameters, including the relative shear thinning. The determined rheological properties were correlated to the amount of total solid glycerides in the blend. It was shown that pumpability of shortenings could be evaluated from selected rheological properties.     

CONSISTENCY OF COMMERCIAL SOYBEAN LECITHINS

Abstract. This study deals with changes of viscosity in commercial soybean lecithins caused by differences in either the phosphatides concentration or in the oil/oleic acid ratio in the acetone-solubles. Viscosity was determined with a plate and cone viscometer at selected constant rates of shear.
The flow curves obtained showed Newtonian behavior only at comparatively low shear rates. Decrease in viscosity due to addition of oil and/or oleic acid was much more drastic in commercial lecithins containing higher (over 65%) concentrations of phosphatides. Addition to commercial lecithins of liquid soybean oil reduced more pronouncedly the products' viscosity than did addition of oleic acid. Samples of commercial lecithins containing less than 2% water were homogeneous and their viscosity was almost unaffected by the water content.