High moisture extrusion - a promising new method for making aquafeed with unique properties

Authors: Liu, Keshun

Submitted to: International Aquafeed Magazine
Publication Type: Trade Journal
Publication Acceptance Date: 4/6/2021
Publication Date: 4/21/2021
Citation: Liu, K. 2021. High moisture extrusion - a promising new method for making aquafeed with unique properties. International Aquafeed Magazine. Available: https://issuu.com/aquafeed.com/docs/aquafeed_vol_13_issue_2__2021/21.

Interpretive Summary: In feeding aquatic animals such as fish, the interaction of feed with an aquatic environment poses problems not encountered in the feeding of terrestrial animals. This makes physical properties of feed for aquatic animals more important than for terrestrial animals. For many years, aquafeed is made by thermoplastic extrusion under low moisture conditions. Compared with prior technologies, such as expansion processing and steam pelleting, the high temperature and low-moisture extrusion cooking has significantly improved both the physical and nutritional quality of aquaculture feeds. Recently, as a part of the Trout-Grains Project, researchers at the USDA Agricultural Research Service in Idaho and Montana developed a new method to make fish feed, featuring high temperature and high moisture extrusion. The high moisture extruded feed possesses some unique features, including soft texture, high pellet durability and water stability. The significance of the new method lies in its representation of an emerging technology for aquafeed industry, its potential to revolutionize feed processing, and its promising alternative to mitigate water pollution issues associated with aquaculture.

Technical Abstract: In aquaculture, poor feed durability and water stability can negatively impact industrial profits and surrounding environments. In fact, the presence of lost nutrients and uneaten feed in fish farm effluent has been a major constraint for expansion of commercial aquaculture. To improve the physical properties of aquafeed, researchers at the USDA developed a new method based on high temperature and high moisture extrusion. The new technology requires a twin-screw extruder, a specially designed die, and careful control of extrusion parameters. Compared with conventional feed techniques, the new method of high moisture extrusion produces extruded feeds with a softer texture, better pellet durability and significantly higher water stability. Furthermore, addition of a carbohydrate binder becomes unnecessary. In this invited feature article, the new method is described, with respect to equipment, processing, product features and its promising strategy for mitigating water pollution issues associated with aquaculture. For more information, readers are encouraged to check our recent peer-reviewed publication (Liu et al. 2021, Animal Feed Science and Technology, 273:114818).