Characterization of food quality and structural stability by analytical centrifugation
Dietmar Lerche¹, Liane Piesendel¹, Bernhard Senge²; Proceedings 3rd International Symposium on Food Rheology and Structure, ETH Zurich, Switzerland, February 9th – 13th, 2003
Abstract: Rheological behaviour and structural properties are important targets during the design of food dispersions and related systems and determine food quality. Rheological approaches are mostly applied to characterize these medium or highly concentrated suspensions and emulsions. Interpretation of results are often difficult due to inhomogenities and demixing phenomena. By contrast analysing the sedimentation kinetics of dispersions in a centrifugal field also yields information about the rheological behaviour and structural stability. Describing the sedimentation of particles and the consolidation of the formed sediment in relation to centrifugal acceleration by the two constitutive materialspecific functions (Kynch flux density, effective solid stress) the mechanical behaviour of particles and gel-like material may be characterised. Experiments were performed in an analytical centrifuge at 11xg to 1140xg (LUMiFuge 114, L.U.M. GmbH, Germany). During the centrifugation the interface between particle free liquid and suspension/sediment of up to 8 different samples was automatically recorded. Sedimentation and consolidation (packing) of different food material (curd, yoghurt, milk, ketchup) was investigated by the approach described above and compared to rheological studies. It was shown that the demixing behaviour and the ability to keep the fluid phase depends strongly on the type of material e.g. curds processing and the fat content. The resulting structural stability parameters correlate well with yield point and thixotropic area obtained from curds and other dairy products. The new approach is a useful tool for efficient development of new food material as well as for quality management systems at the production site.
Key words: Emulsion stability • Food emulsions • Kynch flux density • Yield point • Dairy products • LUMiFuge
¹ L.U.M. GmbH, Rudower Chaussee 29, D-12489 Berlin, Germany; ²Technical University Berlin, Department of Food Rheology, Berlin, Germany.Contact us
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