Two micro-mechanical techniques for studying the enzymatic maceration kinetics of apple parenchyma

• Two micro-mechanical methods were developed for apple texture measurement.
• Methods were applied to study the enzymatic maceration kinetics of apple parenchyma.
• Cyclic micro-compressions referred to peripheral tissues degradation kinetics.
• Micro-punctures referred to internal tissues degradation kinetics.
• Modelling led to an enzyme diffusivity evaluation in apple parenchyma.

The enzymatic texture loss during apple maceration was studied by two micro-mechanical techniques. The first technique consisted of a 5% strain compression cycles at a strain rate of 4.5 × 10−4 s−1. The second technique consisted on micro-puncture of the apple parenchyma with a small needle. The first technique led to the peripheral tissues degradation modelling with a first order kinetic reaction or a more pertinent Weibull function. The second technique evidenced that the jagged part of the load vs penetration curve corresponded to an interaction between the needle tip and the turgescent apple texture and the fractal dimension of this jagged part was chosen as the texture parameter. Modelling the enzyme diffusion phenomenon with the second Fick’s law and taking into account the model previously established on peripheral tissues allowed the estimation of an equivalent enzyme diffusivity through the apple parenchyma varying between 3.5 × 10−11 and 5.5 × 10−11 m2 s−1.