Problems Encountered with a Solid Food

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 

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]. 

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