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Exploring Imperfect Squeezing Flow Measurements in a Teflon Geometry for Semisolid Foods

Authors

  • M.E.J. Terpstra,

    1. Authors Terpstra and Janssen are with Top Inst. of Food and Nutrition, P.O. Box 557, 6700 AN, Wageningen, The Netherlands. Authors Terpstra and van der Linden are with Food Physics Group, Wageningen Univ. & Research Centre, P.O. Box 8129, 6700 EV, Wageningen, The Netherlands. Author Janssen is also with Centre for Innovative Consumer Studies, Wageningen Univ. & Research Centre, P.O. Box 17, 6700 AA, Wageningen, The Netherlands. Direct inquiries to author van der Linden (E-mail: erik.vanderlinden@wur.nl.).
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  • A.M. Janssen,

    1. Authors Terpstra and Janssen are with Top Inst. of Food and Nutrition, P.O. Box 557, 6700 AN, Wageningen, The Netherlands. Authors Terpstra and van der Linden are with Food Physics Group, Wageningen Univ. & Research Centre, P.O. Box 8129, 6700 EV, Wageningen, The Netherlands. Author Janssen is also with Centre for Innovative Consumer Studies, Wageningen Univ. & Research Centre, P.O. Box 17, 6700 AA, Wageningen, The Netherlands. Direct inquiries to author van der Linden (E-mail: erik.vanderlinden@wur.nl.).
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  • E. van der Linden

    1. Authors Terpstra and Janssen are with Top Inst. of Food and Nutrition, P.O. Box 557, 6700 AN, Wageningen, The Netherlands. Authors Terpstra and van der Linden are with Food Physics Group, Wageningen Univ. & Research Centre, P.O. Box 8129, 6700 EV, Wageningen, The Netherlands. Author Janssen is also with Centre for Innovative Consumer Studies, Wageningen Univ. & Research Centre, P.O. Box 17, 6700 AA, Wageningen, The Netherlands. Direct inquiries to author van der Linden (E-mail: erik.vanderlinden@wur.nl.).
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Abstract

ABSTRACT:  The method of imperfect lubricated squeezing flow in a Teflon™ geometry has been explored for the characterization of elongational behavior of custard and mayonnaise. Two Newtonian products, one of low (0.07 Pas) and one of high (18 Pas) shear viscosity, were used as references. Measurements of custards and mayonnaises did not behave according to either the theory of lubricated or nonlubricated squeezing flow, as there were effects of the initial sample height and compression speed. Also, calculated values for the flow index were not as we had expected. The same was true for the Newtonian samples. An important factor explaining the effect of compression speed was the presence of a certain amount of friction, rendering both lubricated theory and nonlubricated theory nonapplicable. Correcting for (pseudo-) thixotropic behavior of custard and mayonnaise appears to be an effective way of obtaining realistic values for the flow index. The presence of buoyancy also affected the results, especially in the case of low viscous products and the effect of initial sample height. Other factors that played a role in the results were yield stress for custard and mayonnaise and instrumental artifacts associated with the imperfect setup of the measurement, especially for the highly viscous products. Quantitatively correcting the results for all of these factors is not possible at this point. Although the imperfect squeezing flow technique in a Teflon geometry is a very practical way to measure semisolids such as custard and mayonnaise under (partly) elongational deformation, the results should be regarded as more qualitative than quantitative.

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