Fish Processing Technology
This section covers Fish Processing Technology: the sequence of operations that turns whole fish into fillets, mince, surimi and formed products, and the yield and quality decisions at each step. The exam tests process logic and calculation of overall yield.
Core rules
- A typical line runs receiving, weighing, grading, washing, beheading, gutting, filleting, skinning, deboning, mincing, forming, cooking or freezing, glazing and packing.
- Keep fish below 5 degrees C during processing and minimise time out of chill. Wash with cold potable water; avoid soaking that leaches soluble protein.
- Surimi processing: mince, wash with cold water around 5-10 degrees C, dewater, add cryoprotectants such as sorbitol, sucrose and polyphosphate, then freeze. Washing removes sarcoplasmic protein and improves gel strength.
- Control blade sharpness and machine settings; dull blades tear tissue and reduce yield.
Worked example
A line takes 1,000 kg whole fish. Fillet yield is 55 percent, mince yield from fillet is 80 percent, and surimi yield from mince is 60 percent. Overall yield = 0.55 x 0.80 x 0.60 = 0.264, or 26.4 percent. Expected surimi = 1,000 x 0.264 = 264 kg. Reasoning: multiply stage yields as fractions; do not add percentages.
Traps
- Washing mince with warm water and denaturing protein.
- Adding excessive phosphate to mask poor-quality raw material.
- Reporting fillet yield without stating whether skin, bone or trim is included.
- Confusing overall yield with the yield of one machine.
- Letting product temperature rise during deboning.