A gelling-agent swelling inhibiter, a jello food packed in an airtight container with an inlet by using the same and a method for inhibiting a gelling agent from swelling are provided to inhibit the viscosity of a mixed solution for jello from rising and a gelling agent from being decomposed by thermal history when dispersing the gelling agent into an aqueous medium. A gelling-agent swelling inhibiter contains a sugar derivative sweetener having a HEAT of fusion of -5.0cal/g or less. A jello food packed in an airtight container with an inlet contains the gelling-agent swelling inhibiter and a gelling agent. A method for inhibiting a gelling agent from swelling comprises the steps of: (A) dispersing a gelling agent and a sugar derivative sweetener having a HEAT of fusion of -5.0cal/g or less into a non-heated aqueous medium to obtain a mixed solution (B) heating the mixed solution, firstly sterilizing and preparing a jello solution (C) packing the jello solution in a container with an inlet and sealing it up (D) secondly sterilizing the packed jello solution and (e) cooling the secondly sterilized jello solution to obtain a jello food.
