page_title: Fish meal
section_title: Processing
hierarchical_section_title: Fish meal / Processing
caption_attribution_description: English: Heogan Fishmeal Factory, Bressay
context_page_description: Fish meal is a commercial product mostly made from fish that are not used for human consumption; fishmeal is generally used to feed farm animals in agricultural setting. Because it is calorically dense and cheap to produce, fishmeal has played a critical role in the growth of factory farms and the number of farm animals it is possible to breed and feed.
  Fishmeal is made from the bones and offal left over from fish caught by commercial fisheries. The vast majority of the fish from which fishmeal is manufactured are not used for human consumption; rather, fishmeal is generally manufactured from by-catch.
  Fishmeal takes the form of powder or cake. This form is obtained by drying the fish or fish trimmings, and then grinding it. If the fish used is a fatty fish it is first pressed to extract most of the fish oil.
  The production and large-scale use of fishmeal are controversial. The lucrative market for fishmeal as a feed encourages corporate fisheries not to limit their yields of by-catch, and thus leads to depletion of ecosystems, environmental damage, and the collapse of local fisheries.
context_section_description: Fishmeal is made by cooking, pressing, drying, and grinding of fish or fish waste into a solid. Most of the water and some or all of the oil is removed. Four or five tonnes of fish are needed to manufacture one tonne of dry fishmeal.
  Of the several ways of making fishmeal from raw fish, the simplest is to let the fish dry out in the sun before grinding and pressing. This method is still used in some parts of the world where processing plants are not available, but the end product is poor quality in comparison with ones made by modern methods. 
  Today, all industrial fish meal is made by the following processes:
  Cooking: The fish are moved through a commercial cooker — a long, steam-jacketed cylinder — by a screw conveyor. This is a critical stage in preparing the fishmeal, as incomplete cooking means the liquid from the fish cannot be pressed out satisfactorily and overcooking makes the material too soft for pressing. No drying occurs in the cooking stage.
  Pressing: The cooked fish is compressed inside a perforated tube, expelling some of its liquids, leaving "press cake". Water content is reduced from 70% to about 50% and oil down to 4%.
  Drying: The press cake is dried by tumbling inside a heated drum. Under-drying may result in the growth of molds or bacteria; over-drying can cause scorching and reduction in the meal's nutritional value.
  Two alternative methods of drying are used:
  Direct: Very hot air at a temperature of 500 °C (932 °F) is passed over the material as it is tumbled rapidly in a cylindrical drum. While quicker, heat damage is much more likely if the process is not carefully controlled.
  Indirect: The meal is tumbled inside a cylinder containing steam-heated discs.
  Grinding: The dried meal is ground to remove any lumps or bone particles.
caption: Fish meal factory, Bressay, Shetland Islands
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