TABLE OF CONTENTS There are two different cases when the food is in a solid state: the one when the solid food is made of grains separated from each other by a gas; the other when the solid is homogeneous as, for example, yoghurts or butter. Only the second case is considered here, the food being in a gel state, however homogeneous and isotropic. Thus the transfer of any additive through the solid food is controlled by diffusion.
The problem of diffusion through a solid food stored into a bottle has already been studied and resolved through various papers. The first when the bottle is made of a virgin layer [20], the second by considering a bottle made of a bi-layer system with a recycled polymer layer and a virgin polymer layer in contact with the food [21], while the third is devoted to the effect of the relative thicknesses of the two layers of the bi-layer bottle [22].
The following assumptions are made to define the process:
The food is either in a solid state or in a gel state, however isotropic and homogeneous.
The process of transfer into, and through, the solid food is controlled by transient diffusion.
Because of the bottle shape, the diffusion is both radial and longitudinal either through the solid food or through the thickness of the bottle.
A perfect contact is obtained at the bottle-food...
