Canned Tuna Processing: Process and Machinery

Canned tuna processing involves multiple stages, from the tuna’s arrival at the facility to the final product presentation, consistently maintaining high hygiene and efficiency standards to preserve the end product’s quality.

In this blog post, we delve into the entire canned tuna processing routine, focusing on the machinery used at different production stages.

Tuna Classification

Once the tuna is received at the processing plant, if it hasn’t been previously sorted by the supplier, the pieces will be sorted. The tuna’s classification in the processing line is a necessary step as it impacts later stages, like cutting and cooking.

This process can be divided into two parts: manual and automatic sorting.

Manual Classification

Manual classification is the first step in the process and takes place right after the tuna offloading. During this phase, the workers make a preliminary selection of the pieces based on their species or remove larger pieces that fall outside the main sorting range.

Automatic Classification

After manual classification, the tuna goes through an automatic sorting process, where sorting machines separate pieces by size. This sorting method is particularly useful in high-volume facilities, as speed and consistency are key to maintain quality and optimize costs.

Tuna Cutting

Before being cooked, the tuna is sliced into pieces of similar size. This procedure is done using saws, specially designed to handle various sizes and types of tuna. The type of saw and slicing technique chosen will depend on the specific requirements of the production line.

It typically starts by removing the tuna’s head then proceeding to make a cross-cut along the body. For larger tunas that may be difficult to manage by one person, a V-belt is applied to correctly position the fish on the saw blade, producing uniform cuts.

Tuna Cooking

The cooking process is paramount in defining the texture, flavor, and nutritional value of the tuna. Primarily, two cooking methods are employed in the tuna industry: vacuum steam cooking and water/brine cooking.

Tuna Steam Cooking

Steam cookers are perfect for large production volumes and cooking tunas that have been previously sliced. They are also recommended for small fishes. This cooking method is commended for its energy efficiency and its ability to regulate temperature accurately.

Steam cookers provide even cooking and mitigate the risk of overcooking thus preserving the tuna’s characteristics. Additionally, retrieving oils and fats released during cooking can be an extra advantage; it allows their sale as a value-added by-product.

Water/Brine Cooking (Tuna Cooking Blanchers)

On the other hand, tuna cooking blanchers sused for water/brine cooking are primarily applied to smaller tunas and smaller production runs. Nevertheless, this method is less energy-efficient compared to steam cooking, becoming less attractive for large-scale producers.

Additionally, it implies added investment costs in complementary facilities such as water purification stations or humidification and cooling chambers for the cooked tuna, typically installed post-cooking.

Tuna Cleaning in the Processing Line

The cleaning stage is carried out prior to packaging and sterilization. This process involves the removal of waste, separation of unwanted parts, and preparation of the tuna for the final stages of production. It is a manual process, where each operator has their own workstation.

Tuna Cleaning Line

Tuna cleaning lines can be classified into two main types: straight and circular lines. Straight lines are traditional, where the tuna moves through a central conveyor for processing.

On the other hand, circular lines offer a more ergonomic and efficient approach, allowing for continuous flow and reducing the risk of jams. This design enables operators to access the tuna from various points, improving both ergonomics and process efficiency.

At Gaictech, the cleaning lines we manufacture are highly ergonomic and adaptable to the available space in the plant, with the possibility to design individual stations for each operator.

Tuna Cleaning Line Control Software

A crucial component in modern cleaning lines is the control software, which allows for monitoring and optimizing cleaning performance and times.

This system not only helps improve operational efficiency but also enables the implementation of productivity-based incentive schemes, aligning workers’ interests with the company’s production goals.

Pin-Bone Remover

After the cleaning process, parts of the tuna waste generated (small bones, skins, cartilage, etc., mixed with crumbs or small pieces of tuna—central bones are not included), are collected and placed into the pin-bone remover machine.

This machine separates the tuna crumbs or small pieces from the bones, cartilage, and skins of the tuna, utilizing this white meat and cleansing it from foreign elements, thus achieving an additional percentage of clean white meat for packaging in the subsequent process.

Tuna Packing

Packing is the process by which tuna is placed into containers. There are different packing methods depending on the final product desired.

Packing Methods

• Glass Packing: This method is done manually, allowing meticulous control over the quality of the final product. It is ideal for premium presentations where the aesthetics of the product are essential.
• Can Packing: Uses automatic packers that ensure precision in filling weights and high operational efficiency. This method is common in mass production, where uniformity and speed are critical.
• Pouch Packing: his packing method also employs advanced automatic machines that ensure efficient and precise filling and sealing. It is ideal for individual presentations or specific portion sizes. There is also an option for manual packing.

Covering Liquid Dosing

Covering liquid dosing is the process by which a liquid, typically oil or salt water, is added to the packed tuna. This liquid is used to maintain moisture and enhance the flavor of the product, as well as to achieve an efficient seal by eliminating any residual air between the tuna patty and the closure.

Precision in the amount of liquid added is crucial to ensure consistency of the final product and to avoid issues during subsequent processes.

Tuna Can Sealing

The sealing of the cans ensures the tuna’s airtightness and preservation. This procedure is executed using seamer machines that apply specific pressure to securely and efficiently seal the can lids.

Based on the package type, various models are present, related to the can’s geometry and speed. Likewise, if the lines represent glass bottles or pouches, multiple models are there based on container types or speeds.

Package washing

After sealing the can, it travels from the seamer to the can washer.

Gaictech’s can washer is a machine engineered to clean any kind of container, incorporating cans and pouches. This machine is renowned for its ability to efficiently discard residues and recover surface oil, without involving detergents. Hence it contributes to a more sustainable and economical process.

Basket Loading of Autoclave Carts

Post washing the cans, they go to the basket loader, where cans are systematically arranged in layers inside the trolley, separated by a plastic separator. Once the trolley is full, it is redirected to the autoclaves to initiate the sterilization process. Depending on the needs of the production plant, the type of container, and the speed of the production line, varying degrees of automation can be implemented in this process.

Depending on the needs of the production plant, the kind of container being handled, and the speed of the production line, varying automatization degrees can be implemented for this process.

Sterilization Process in Autoclaves

The sterilization of tuna in an autoclave is a necessary step to ensure food safety and the product’s long-term preservation. This process employs high temperatures and pressure to remove pathogenic microorganisms and enzymes that can spoil the tuna.

Autoclaves can function with manual, semi-automatic, or fully automatic loading systems, providing flexibility adapted to the production volume and each plant’s specific requirements.

In this process, the sealed cans are placed in trolleys (in the case of pouches or flexible containers, in cage-like structures that are stackable). These trolleys are introduced into the autoclave, essentially a large pressure vessel, designed to endure high temperatures and pressures.

The autoclave is filled with steam or fed superheated water (depends on the working system chosen), causing gradual heating until an internal temperature of 115°C-121°C (239°F-250°F) is achieved in the autoclave over a certain period, depending on the container type being sterilized. This eliminates microorganisms and enzymes.

Afterwards, the cans are gradually cooled with cold water following the programmed parameters, to bring them out at an optimal temperature for subsequent handling

If you want to learn more about the types of autoclaves in the food industry, we have created an article that you can consult here.

Unbasketing

Once the cans are sterilized and basketed, the first step in the production line is unbasketing, where cans are taken out of the trolleys to be processed individually.

Depending on the needs of the production plant, the kind of container being handled, and the speed of the production line, varying automatization degrees can be implemented for this process.

Drying and Labeling (as needed) of the cans

Drying: Post sterilization and unbasketing, drying is crucial to ensure that the cans are thoroughly free of moisture ahead of the final packaging or labeling.

In Gaictech, for example, our can dryers incorporate heat exchangers and air-knives to dispense hot air, effectively eliminating any water residue.

Labeling: Depending on whether the can is lithographed or not, the process varies. If it is not lithographed, it is labeled using labeling machines. Lithographed cans already have the design printed directly on the metal and do not require additional labels.

Boxing (if applicable) and Storage

Lastly, depending on the desired configuration and the target market, cans can be put in packages, such as tripacks, bipacks (or other options), or individual boxes. This process can be automatic or manual.

Cans or boxes are grouped and placed in boxes, but there’s also an option to group them and cover them with transparent shrink wrap. This step can be automatic or manual, and then later stored.

Conclusion

Canned tuna production is a complex process that necessitates highly specialized equipment and precise coordination among multiple stages. Each step is vital from the receiving of raw materials to final packaging, to ensure the final product is of the highest quality.