Effect of Moisture on the Mechanical Properties of Pork Rind (Chicharrón)

Abstract

Pork rind particles of two commercial brands were tested at various water activity levels in the range of 0.1-0.8 and compressed as shallow bed using an Instron universal testing machine. The jaggedness of the resulting force-displacement curves was determined in terms of their apparent Richardson and Kolmogorov fractal dimension and the mean magnitude of their power spectrum after normalisation. The bed's stiffness was assessed in terms of the compressive force at 25 and 35% displacement. The jaggedness decrease, which corresponds to brittleness loss, took place around the water activity of 0.5 with a span of about 0.2. Sorption at levels up to about 0.5 was accompanied by `moisture toughening' that is the bed's stiffness measures increased with aw. There was a sharp decline at higher water activity levels as the structure collapsed. The changes in the brittleness and stiffness parameters as a result of moisture sorption were modelled with the Fermi and a combination of Fermi and the logistic equations, respectively.