Retorting is a process where food is heat-treated inside the package. The heat treatment is applied to generate a commercially sterile product that is stable in ambient conditions prior to opening.
Yes, carton packages can be retorted just like tin cans, glass jars and plastic pouches. The retortable carton is a one-piece container that is filled unsterile and is processed after the container has been sealed. The flat carton-fed system enables filling of a large range of viscous product and particle sizes dependent on the type of filler and machine platform used. It has a laser perforation to enable easy full-top opening of the package.
Food preparation can include steps such as peeling, cutting, blanching, soaking, frying mixing and so on. The prepared food product can be filled into the carton package in one or multiple steps, depending on the food type and the selected filling solution.
After sealing, the carton package is then heat-treated in a retort, also known as an autoclave, to achieve a commercially sterile product.
The ultimate aim is to produce safe food products of high quality. So the temperature and retorting time required for a specific food product needs to be thoroughly evaluated before being implemented. Generally, 121.1°C is required for sterilization. For products with pH below 4.5, pasteurization temperatures can be applied. A normal retort process usually takes between 60 and 180 minutes in total.
The goal when retorting is to retain the highest possible product quality without compromising on food safety. By using the lowest possible temperature in combination with the shortest possible heating time, the product is kept fresh. Therefore, the heat treatment process is optimised for each product.
Tomato products, beans, fruits, vegetables soups, ready meals, baby food and even petfood can be found in carton packaging today. The process is ideal for any food that can be sterilised or pasteurised to make it safe on a microbial level. Limitations relate to if the food can maintain its taste and freshness after heat treatment.
Yes – a continuous processing line with aseptic filling of carton-based packages. This method is commonly used for beverages and dairy products but is also suitable for viscous foods. The food product undergoes heat treatment in a steriliser, before being filled in sterilised packages in a completely aseptic environment.
The main difference between these packaging solutions is that a retortable carton is constructed to fully process the product inside the package when sealed, while aseptic packaging maintains a product that has been fully processed before filling. Both packaging solutions include barriers to maintain high product quality during shelf life.
It is made of six layers: four of polypropylene, one of aluminium, and one of paperboard. Paperboard – a renewable material – makes up at least 69% of the package.
The structure enables the material to withstand water exposure during the retort process and provides a suitable environment for a wide variety of products, while meeting demands for a long shelf life.
The machine that heat-treats the package for sterilisation purposes is known as either a retort or an autoclave.
Steam water spray retorts are commonly used for retortable cartons. The retort equipment is standard for the industry, but the packages require a specific rack to enable an even heat treatment during processing, while maintaining the integrity of the packages.
During the retort process, it is important to maintain an outer overpressure high enough to balance the internal pressure in the package generated by the food product. Too low or lost pressure in the retort during processing will result in package deformation. Controlling the overpressure in the retort is important in all processing steps, including come-up, holding and cooling.
After retort processing, excess water on the packages is removed using a fan to dry the surfaces. The packages are then grouped into secondary packaging before being stacked on a pallet.