closure systems for food containers , and methods for mixing foods in portable containers is disclosed , using new apparatus for closing portable containers to store and transport foods , and new processes for mixing those foods prior to final or on - site dispensing and use , in which the food mixing takes place within the container , generally prior to its opening , as chambers or compartments within a container are opened to other chambers or compartments within the same container by transmission of pressure or tension from the exterior of the container , to one or more points , lines , or channels in one or more walls of chambers within the container , thereby opening one or more channels between such chambers through which food , fluids , or materials may travel .