TABLE OF CONTENTS This is the most common case of release of some additives taking place from the polymer package into a liquid food. The process, controlled either by diffusion through the thickness of the package or by convection at the solid-liquid interface, has been described in Chapter 1, as well as in Section 4.2.
The principle of the process is depicted in Figure 4.1 where the scheme is drawn.
The thickness of the package is L, with: 0
The process is controlled either by diffusion through the thickness of the package or by convection into the liquid food;
When the diffusivity is constant and the initial concentration of the diffusing substance is uniform, the mathematical treatment is feasible, leading to an analytical solution. When one of these two requirements is not complied with, a numerical analysis should be made leading to a numerical model with finite differences;
When the volume of liquid is larger than that of the package, with ?>20, the mathematical treatment is feasible, otherwise, the numerical model should be used.
As shown already, because of the convection in the liquid, the concentration of the additive is uniform in the liquid at any time. Thus, the one-dimensional transfer can be considered, per unit area.
