Aquafeed twin screw extrusion processing
2006
Brisset, A. | Bouvier, J. M.
Aquatic feeds require specific physical and nutritive properties and have to comply with the fish behaviour. Fish meal and fish oil are frequently used as raw materials together with cereals (binders) and additives such as vitamins and minerals. Other protein sources are found in the diets to complement or replace fish meal, for example soybean flour. Fish oil can be partly substituted by vegetable oils. Aquafeed extrusion processing lines consist of well defined unit operations which aim at converting feed mixes into texturized, shaped and stable aquafeed pellets. Such unit operations including raw mix preparation (grinding in particular), extrusion processing, drying, fat coating and cooling are discussed. Special emphasis is presented on those unit operations which affect the quality of aquafeed pellets. These include pre-conditioning of feed mixes (heat balance, hydration time. and residence time distribution), thermo-mechanical cooking in twin screw extrusion processing and aquafeed pellet texturization (control of SME and pellets density, in particular).
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