A Video‐based Method for Determination of Average Stress‐strain Relations in Uniaxial Compression of Selected Foods

Abstract

A video-based method was applied to evaluate average stress-strain relationships during uniaxial compression experiments of selected food materials. f i e determination of apparent Poisson ratios of Gouda cheese resulted in numbers close to the theoretical value for incompressible materials of 0.5. In case of such foodstuffs, mathemaheally corrected compressional stress based on the consideration of constant specimen volume showed almost similar results to stress values estimated on the basis of the true cross-sectional areu measured from lateral extension. For compressible materials such as apples or bread, which show a certain reduction of volume under stress or strain, the apparent Poisson ratios were strain-dependent. Average stress values calculated from compressional force and actual specimen diameter were found to be different from either engineering stress and corrected stress.

Density dependent mechanical properties and structures of a freeze dried biopharmaceutical excipient – Sucrose

“…The Poisson's ratio is further reduced as embrittlement is increased in materials [37]. Both starch and sugar foams are similar to that studied here such as sucrose, trehalose and mannitol have reported Poisson's ratio around 0.2 [38,39]. Considering these reported values, it is assumed that the Poisson's ratio for all freeze-dried, brittle, cellular cakes used in this study is 0.2.…”

Visualization of planar stress distributions in cucumber cultivars using a multiple‐point sheet sensor

“…To calculate the actual stress that takes into account the change in shape, the increase in the cross-sectional area during compression was estimated assuming a constant specimen volume. 15,16 If the assumption of constant volume (or Poisson's ratio of 0.5) was uncertain, the change in cross-sectional area was estimated by monitoring the lateral extension by a video-based method 16 or through direct measurement by the MSS. 11 The change in the cross-sectional area of the cucumber specimen was directly monitored by the MSS system.…”

Texture properties of Slovak Bryndza measured by instrumental analysis

“…Fundamental rheological tests reveal important information in relation to network structure and molecular arrangement (González-Vinas et al, 2007). Uniaxial compression is a standard technique for rheological testing of cheese and has been employed to evaluate the texture in various types of cheeses including Italian cheeses (Lucisano and Pompei, 1985), Manchego cheeses (Fontecha et al, 1994), Gouda (Rhom et al, 1997), Cheddar (Gwartney et al, 2002), Swiss cheeses (Pesenti and Luginbuehl, 1999), Feta (Tsigkros et al, 2003) and in hard and semihard cheeses (Gohs et al, 2003). The uniaxial compression technique gives information about the mechanical and fracture properties of cheese at large-scale deformation (Zoon, 1991;Luyten et al, 1992).…”