In a seafood processing plant, grading is the practice of sorting fish into similar groups. Even if a production line is handling a batch of the same fish species, they might vary considerably in size, weight and quality. As you might imagine then, grading is a vital part of the fish processing business, as both modern retail suppliers and their customers demand extremely uniform, consistently packaged products.
The most common fish grading methods used today
Generally speaking, the fish processing industry uses three main methods for grading products as they enter the production line. Each method has its advantages and disadvantages, depending on several factors, including the fish species and the type of end-product being created.
Grading fish mechanically
Mechanical grading commonly uses vibration or roller grading machines to sort fish by width or thickness. Modern machinery, such as the equipment made by Latvian experts, PERUZA, is incredibly precise, making mechanical grading perfect for small, delicate species such as sprats or Baltic herring, as well as sardines, pilchards, and anchovies.
Here are the main advantages of mechanical grading:
- Increased productivity, with up to 8 tonnes of fish processed per hour.
- Roller and vibration fish grading usually causes less damage to produce.
- A low number of operators are required to keep the machinery running.
Grading fish by weight
Grading fish by weight is often used to sort low-yield, high-quality products, including salmon, crabs and lobsters. Modern weight grading lines work by feeding products into a Z-type conveyor, one per pocket, and then to an acceleration conveyor. Finally, each product is weighed separately in a flow-weight conveyor unit, with the figure compared to the correct exit gate grade and then transported to the corresponding exit gate.
The main benefits of a weight-based fish grading system are as follows:
- For oddly-shaped products, a weight grading line offers increased precision.
- 120 products can be sorted per minute using the latest machinery.
- Expensive products such as salmon and lobsters are less prone to wastage.
Grading fish visually
As the name implies, visual grading involves sorting fish into batches depending on their visual appearance. Visual fish grading can either be performed manually by a human operator or via robotic fish grading equipment, which has been programmed to differentiate between several distinguishing features.
Whether a robot or human operator is used, a visual fish grading system can be used to sort fish into separate bins according to size or species — though modern, automated machinery offers several key benefits over human workers:
- Fewer operators are needed, as robotic machinery can achieve a high turnover without becoming tired or distracted.
- Robotic vision has proven to be highly effective and precise at differentiating between different sizes and species of fish.
- Workforce reductions and lower failure rates make visual grading by robots a good return on investment.
Summing up
Grading is a highly important task in the fish processing industry, and the right equipment can bring enormous benefits. As robotics and automation become more commonplace, it will become vital for business owners to understand how to choose the best fish grading system to stay ahead of the competition.
