A container (1) for preparing a nutritional composition from a powdered nutritional base formula or liquid concentrate, the container (1) comprising: - liquid inlet means (6) designed to be supplied with liquid from about liquid distribution means (20), - an adapter (4) being provided with coupling means (2) connectable to matching coupling means (20a) of the liquid distribution means (20) for connecting the container ( 1) to the liquid distribution means (20), and - a flexible wall portion (31, 3b ', 3b "), connected to the liquid inlet means (6) and at least partially defining a compartment ( 3) containing a predefined amount of powdered nutritional base formula or liquid concentrate (5) for the preparation of the nutritional composition (5a) after hydration with the supplied liquid, in which the flexible wall portion (31, 3b ', 3b " ) is expandable so that the volume of the compartment increases from a retracted position to an expanded position that allows a sufficient volume of liquid to be supplied in the compartment (3) through said liquid inlet means (6) for preparation of the nutritional composition, characterized by the fact that the flexible wall portion (31) is any one or a combination of the following expandable structures: - an accordion type structure, - a stepped structure, - circumferential lines of weakness or of reduced thickness in the material itself or, - the flexible wall portion (31) forms a folded portion of the bag designed to be deployed after the introduction of liquid into the compartment (3).Un recipiente (1) para preparar una composición nutricional a partir de una fórmula base nutricional en polvo o de concentrado líquido, el recipiente (1) que comprende: - unos medios de entrada de líquido (6) diseñados para ser suministrados con líquido desde unos medios de distribución de líquido (20), - un adaptador (4) estando dotado con unos medios de acoplamiento (2) conectables a unos medios de acoplamiento coincidentes (20a) de los medios de d
