The tuna canning industry Is still staying steady even with the escalating price of raw tuna. This makes it much more important to emphasize on processing methods and techniques to help keep product cost down and to make the operation much more efficient. We have now completed filling & sealing and will proceed to retorting and can cooling.

Once the filled and sealed cans exit the seamer/can washer, it is then staged for retorting(sterilizing). At this point, it is very important that the delay time before the cans are actually retorted be monitored very carefully. It is not only a major safety factor for under sterilizing but also a factor for causing swollen cans and other defects. It is a required and good practice to place the sealed cans into the retort and start sterilizing as soon as possible. There are several types of retorting methods such as horizontal still retorting, continuous crateless, hydrostat, and others. The most commonly used is the horizontal still retort system. It consists of a horizontal round vessel in which baskets are placed within using an entrance door and taken out through an exit door. The times, temperature and complete process is controlled automatically  by a type of PLC system. The heating medium is steam and the cooling  medium is water.

There are two types of baskets and methods for placing the cans in the retort basket. It is called jumble where the cans fall into the basket without any type or orientation while the busse system is where the cans are evenly layered throughout the basket. This requires a square basket while the jumble loading requires either a round or square basket. The more preferred is the busse or layer system as this will minimize can damage and shorten the retort time. In addition, this will reduce the amount of scorching that you will visually see in the canned product. Scorching is a quality defect that customers continue to complain about due to its brownish appearance when the can is opened.

After the sterilizing process has been completed, the cans are pre-cooled within the retort vessel with water so that the cans do not bulge or swell up while they are cooling down slowly from the high sterilizing temperature. Once the baskets are removed from the retort, the cans require additional cooling before they are hermitically sealed. This is a required safety factor and should be followed very closely. It requires a sanitary area that is isolated and free from any contamination. Normally the cans are left in this area overnight then placed either in cartons or labeled the next day. If the cans need to be labeled the same day, then large electric fans are placed directly in the area for faster cooling. If square baskets with layered cans are used, then the baskets are tilted on an angle to allow any excess water on the surface of the cans to run off so that the cans are dried.

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