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vol. 13, nr. 3 (2009)
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Application of squeezing flow in measurement of rheological properties of apple pulp
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Ewa Jakubczyk
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Department of Food Engineering and Process Management, Faculty of Food Sciences, SGGW-WULS ul. Nowoursynowska 159C, 02-776 Warsaw |
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vol. 13 (2009), nr. 3,
pp. 673-684
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abstract:
The objectives of this work were to assess the effect of velocity at the range of 0.1-2.0 mm s-1 and the diameter of compression plates on rheological parameters of apple pulp. Additionally, foamed apple pulp with additives was analysed. The rheological properties were investigated by squeezing flow test based on compression of a specimen between parallel Teflon plates with different diameters of 61 and 120 mm. The reproducibility of the results determined by using plate of 120 mm in diameter was higher than for those obtained with plate having 61 mm in diameter. The coefficient of variation of apparent stress did not exceed 4 and 29% using plates of 120 and 61 mm in diameter, respectively. The values of flow index n of pulp obtained with the 120 mm plates varied between 0.698 and 0.807. Statistical analysis showed that the optimal value of test velocity was 0.2 mm s-1. The average value of flow index of foamed pulp was about 0.631. The foamed pulp had a high value of non-relaxed stress ratio, which indicated that the foamed material had a yield stress of considerable magnitude.
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keywords:
rheology, squeezing flow, apple pulp
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original in:
Polish
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