This invention provides an apparatus for simulating digestion of a foodstuff, which apparatus comprises:(a) an outer containment vessel into which fluid can be introduced and removed via at least one orifice, and(b) an inner digestion chamber comprising a rigid portion through which the foodstuff can be introduced and a flexible portion which tapers from the rigid portion to an aperture from which the foodstuff can be removed, wherein said inner chamber is securable within the outer vessel such that reversible alteration of fluid pressure within the outer vessel causes reversible partial compression of the flexible portion for mixing foodstuff present therein. The invention also provides systems and methods for simulating digestion of a foodstuff.