The processing of raw material for fishmeal and fish oil production essentially follows a cooking, pressing, extraction and drying cycle that separates out the fishmeal and fish oil, producing only condensate as a byproduct. In effect, a product that incorporates all the raw material other than a major fraction of the water it contained is produced. Processing follows strict quality management procedures to ensure that end product specifications are within recognized ranges for nutrients and contaminants. The process is highly technical in order to retain the nutrient qualities in the raw material as much as possible, and ensure that these are fully recovered to the end products of fishmeal and fish oil.
Quality standards are upheld using best practice and traceability all the way from high seas catch via modern fishmeal and fish oil processing techniques through to the end user.
Fish is first typically cooked to coagulate protein and allow some oil to be released, using a temperature from 85°C to 90°C. In addition, micro-organisms are killed by this process. Clean conveyors, holds and storage pits, short storage time and reduced temperatures minimize micro-organisms and the spoilage they may cause. The lower temperature also reduces fish enzyme activity, another form of spoilage. Cooked fish then passes into a screw press where liquid is pressed out and the solids (press-cake) go to the dryer.
The liquid is decanted to remove further solids. It is then centrifuged to spin off oil and separate out an water phase (protein water). The protein water passes through evaporators to reduce its volume (concentrate). This concentrated liquid (called stickwater because it tends to be viscous and sticky) is returned to the press cake entering the dryer. A typical disk dryer is designed with a large heating exchange area. Fresh steam would pass the hallow disk and rotor as well as the jacket to evaporate the moisture of fishmeal. It is what we call a indirect vacuum dryer. After dryer, the fishmeal will be cooled, screened, and packed, ready to be sold on market.
Fish oil will be stored in a fish oil tank, it is a feed grade fish oil where it could be sent to a fish oil refinery system for dietary or pharmaceutical use.