Flexible walled containers of various sizes are often used to store and/or transport liquid food under sterilized conditions. A container of this type often consists of at least a pair of multi-ply structured walls, and a spout for receiving and dispensing food products. The spout is generally applied on one side of one of the walls by means of heat-sealing and can be closed by a plug or cap. The plug or cap for the spout can be either a separate part applied from the top of the spout, or be an integral part of the bag heat-sealed to the opposing wall from the spout. The latter has shown many advantages in aseptic filling including oxygen prevention, sterilization and bag management.
Containers known in the art include those having both the spout and plug made of same material that is relatively stiff compared to the material for the container. To enforce a liquid tight seal, an O-ring is generally used between the plug and the spout. Prior to use for packaging, the containers are completely sterilized by gamma rays. Then the bags are transported to the food packaging manufacturer. Since during storage, transportation and preparation for filling, the outer surface of the bag and spout/plug may be exposed to the environment and lose sterility, the seal at the fitment is critical for keeping sterility inside the container.
At the filling station, before the food can be introduced into the bag, sterile conditions have to be restored for any part of the bag that could get into contact with the food during the filling process. For example with the filling method described in U.S. Pat. No. 4,731,978, the only parts that need to be re-sterilized for this type of bag are the rim of the spout, the top surface of the plug, and the crack between the plug and the spout before the seal is formed with the O-ring. To sterilize these parts, they are flushed with steam for a certain period of time. However, a uniform temperature at these places is not ensured in a short-term steam flush. At the crack before the O-ring, lower temperatures may occur, leading to a potential health safety problem. Therefore, a prolonged steam-flushing time is required for this design. In addition, a cap on top of the fitment is generally used to minimize the risk of contamination. The O-ring, in such a design, being a separate part of the plug may be displaced on the assembly line, or during the open and close procedures. Furthermore, these extra parts on the spout/plug make the fitment assembly time consuming and costly.
When the filling process is finished, the plug from inside of the bag closes the spout. Since the plug is pulled into the bag during the filling and the sleeve of the spout is part of the channel for food flow, both surfaces may be covered with food after filling. Although steam flush cleaning is generally used during the closing stage, complete cleanliness on both plug and spout surface may be difficult to achieve, particularly for food with high viscosity. In this case, food may be caught in the pockets formed around the O-ring and in the crack between the plug and the spout. Although these foods have no impact on the food inside the bag, they are exposed to the environment after filling and are a potential source of contamination. If the spout is to be used for dispensing, this part will be very difficult to be cleaned and sterilized again.