PURPOSE: To produce the subject retort pouch food capable of effectively preventing, e.g. generation of a special harsh taste or a special stuffy odor or occurrence of cloudiness, etc., in a soup without requirement for an additive, etc., by bringing water into contact with an ion-exchange resin when heating the foodstuff in the presence of water before retort treatment thereof.

CONSTITUTION: When initially heat treating a foodstuff such as a vegetable or a meat in the presence of water the heat treatment is carried out in a state where water is in contact with an ion-exchange resin. The heat-treated foodstuff is then subjected to retort treatment according to the conventional method. Specifically, the above-mentioned heat treatment is carried out recommendably by connecting a heat treatment tank for heat-treating the foodstuff through pipes to an anion-exchange resin tank packed with an anion-exchange resin in layers and circulating water between the heat treatment tank and the anion- exchange resin tank. In addition, the temperature and the time in this heat treatment are recommendably 60 to 100°C and 2 to 30min respectively.