The process

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Commodity · §03

Wet pressing still makes the bulk of the world's fishmeal^[1] — a five-step line that has barely changed in principle for a century.

The design problem is simple to state: raw fish is roughly two-thirds water and a tenth or so oil, and the product must be a dry, stable powder. Wet pressing solves it with heat, pressure and centrifuges, in a continuous flow from landing crane to bagging line.

Cooking

Raw fish is steam-cooked to coagulate the proteins and break the tissue so that oil and water can be released.

Pressing

The cooked mass is squeezed in screw presses, splitting into a solid press cake and a liquid press liquor.

Separation

Centrifuges split the liquor into fish oil, stickwater and sludge. The stickwater is evaporated down to concentrated solubles, usually added back onto the cake — which is why "whole press liquor" matters on a specification.

Drying

Cake plus solubles are dried (direct or indirect heat) to a stable moisture level; overheating here costs digestibility.

Milling & storage

The dried meal is milled, often antioxidant-treated, and stored or bagged for shipment.

Anchor figure — cooking for coagulation, pressing, liquor separation, drying, milling: the multi-source standard description of the wet pressing line.

Where quality is won or lost. Freshness of the raw material sets the ceiling; the drying step sets the floor. That is why specifications track volatile nitrogen (raw-material freshness) and digestibility (process heat) with equal suspicion.

Sources

FAO — The production of fish meal and oil, ch. 3 — www.fao.org/4/X6899e/X6899E04.htm (accessed 2026-10-24)
Agriculture Institute — step-by-step guide — agriculture.institute/fish-by-products-waste-utilization/step-by-step-gu (accessed 2026-10-24)