Almost every product sold in a can – from evaporated milk to soups and tomato purée – needs to be subjected to a high temperature before it leaves the factory floor to eliminate any potential bacterial threat, from botulism to salmonella.
With some systems, this is a labor-intensive process, with batches – or cubes – of cans having to be packed into static cookers, heated up, and then cooled down before the next batch can be introduced.
JBT’s Continuous Rotary Sterilizer product line – recognized as an engineering landmark by both the American Society of Mechanical Engineers (ASME) and the American Society of Agricultural Engineers (ASAE) – is a system that has single-handedly revolutionized can sterilization.
Employing a circular, rotating cylinder and paddle wheels that agitate cans as they are passed through, the Continuous Rotary Sterilizer range is effective, efficient and ensures that contents are thoroughly cooked, eliminating the risk of bacterial contamination.
So successful has the Continuous Rotary Sterilizer line been that approximately half of all the world’s canned goods are now processed using the system.
How it works
“The JBT Continuous Rotary Sterilizer can process most foods filled into a cylindrical can that need a high temperature applied to it,” explains JBT Application Engineering Manager Mike O’Hara.
This covers a wide range of products from milk, fruit juices, soups, many types of fruits and vegetables even including pasta-type products. Most products are mixed up in vats and then filled into the container. The container is sealed and then sterilized in the sealed can so no bacteria can get in.
Previous systems used a still cook process where cans would be stacked inside a static vessel and subjected to a high temperature. Typically the problem with this method was inconsistency in the cook between the center and outside of the stack; the outermost containers would be overcooked. This could cause browning or caramelization, especially in milk which consumers would not accept.
Where the rotary really brings benefits, says O’Hara, is through agitation.
The JBT Continuous Rotary Pressure Sterilizer is available in two diameters – a roughly 60” model and a larger 112” model – both of which are relatively simple to operate.
“You have a cylindrical tube with a spiral helix welded to the interior of the tube that advances the cans down the length of the sterilizer,” explains O’Hara. “Inside the tube, the cans ride on a paddlewheel type device that provides a rotational motion. As the cans are pushed down the side of the vessel, the cans will roll providing a mixing action – this is key in providing a consistent cook, better product color and taste.”
With the mixing action, the heat penetration is faster and reduces cooking time verses other methods. Another big benefit, O’Hara says, is that each container experiences the same process in the Rotary Sterilizer, unlike static retorts where a difference is commonly seen from the interior can of a stack to the cans on the edge.
The length and number of vessels can vary depending on what you are cooking. A light broth will typically cook quickly in one 20 foot long vessel, while a heavy soup may require two or three 40 foot long vessels. The containers are also cooled back down in a similar way.
“With all the different types of food being processed in the world, we are set up well to design a good solution for each application,” adds O’Hara.
Now manufactured at sites in California, Belgium, and South Africa, the Continuous Rotary Sterilizer is available and widely used by manufacturers in countries worldwide, from the Americas to Asia, attracted by the advantages that the product line offers.
The Continuous Rotary Sterilizer product line includes pressure vessels for products that are subject to botulism and need to be cooked at a higher temperature, as well as atmospheric vessels, using a process similar to pasteurization, where E.coli or Salmonella is the threat. For example in tomato products, lower temperatures can be used to kill the bacteria without affecting the contents.
Another key advantage is the efficiency of the Continuous Rotary Sterilizer system.
“The rotary is very efficient – once you heat up the vessel, can go into the paddlewheel spiral, through the vessel, and pop out the other end in a continuous 500 cans a minute (or faster) cycle,” explains O’Hara.
“With a batch retort system, you put the batch in, raise the temperature and then you have to cool all the product and machine before putting in a new batch and heating it up again, so you are always heating and cooling,” he says. “With the continuous rotary, once you heat it up you are ready to go.”
Compared with other systems, notably batch retort, O’Hara says the Continuous Rotary Sterilizer is also far less labor-intensive.
“With batch retorts, you have to have a pretty complex loading and unloading system, oftentimes it’s manual,” he says.
“But with a rotary, the cans come out from the filler and seamer, roll into the cooker, and away they go. One operator can watch five or six lines, whereas with a batch system it depends on how you are loading and unloading the containers – there is that extra step there.”
Potential problems are also avoided by an inbuilt validation system that tracks critical control points and alerts the operator if there is any deviation from the intended recipe.
Although not the cheapest option from a capital investment standpoint, with saving on utilities and reduced labor the rotary can save money in the long term. In some cases, the Continuous Rotary Sterilizer offers a typical return of investment in under two years.