Fermentation pressure pack

A two component pressure resistant pack having a fermentation mix therein comprising an inner bag component and an outer bag component, the inner bag component being fluidtight and formed of a flexible plastics, the inner bag component having an inlet including a pressure relief valve and having an outlet tap, the outer bag component being pressure resistant, the valve and the tap of the inner bag component protruding through holes therefor in the wall of the outer bag component, the inner bag component having a sealed margin about the sides thereof, the margin being folded so that upon an increase in pressure therein caused by fermentation of the fermentation mix therein, the inner bag component will expand and trap the folded over margin between its wall and the facing inner wall of the outer bag at spaced apart locations where the outer bag component then supports the inner bag component against the pressure therein while allowing for portions of the bag wall between the supported locations to expand further.