2.6. Evaluation of mechanical properties
Mechanical properties of fresh and dehydrated samples were
analyzed through uniaxial compression test (TA-XT2i Texture
Analyzer with a 60 mm acrylic plate). Pineapple slices were cut out into 25 mm-diameter discs.
The applied compression rate was 0.5 mm/s, until 50% sample deformation of the original height. These assays were performed on five samples from different processed slices; then these five measures were averaged. Also, force F(t)(N) and height H(t)(m) data were recorded. These data were turned into Hencky parameters: stress (_H) and strain (εH), by assuming constancy of sample volume during compression test), according to Eqs.
where Ao (m2) is the initial contact area, Ho (m) is the sample height at beginning of compression test and H(t) is the height
after a deformation time t. Stress (_HF) and strain (εHF) at fracture were determined at the maximum point of stress–strain curve. The elasticity or deformability modulus (E) was calculated from the slope of the initial linear portion of the stress–strain curve when sample deformation (small-strain) was not higher than 6%