Journal of Animal and Feed Sciences, 26, 2017, 165–171 https://doi.org/10.22358/jafs/74423/2017 The Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, Jabłonna The infuence of expansion control device used during production of different extruded sea bass feeds on pellets quality A. Kop 1 and A.Y. Korkut Ege University, Faculty of Fisheries, Department of Aquaculture, TR-35100 Izmir, Turkey KEY WORDS: fsh feeding, pellets, expansion, extrusion, feed evaluation Introduction The high-temperature-short-time (110–204 °C/ 10–20 s) extrusion cooking technology is usu- ally used in the production of the aquaculture feeds (Hardy and Barrows, 2002; Glencross and Hawkins, 2007; Sørensen et al., 2009). The advantages of such thermal treatment as extrusion comprise: achieve- ment of a desired physical form, inactivation of some antinutritional factors (Melcion and van der Poel, 1993), prolonged shelf-life, increased nutrient di- gestibility and enhanced palatability. In addition, the starch is gelatanized during the extrusion and in effect becomes more digestible for enzymes of carnivore fsh (Bergot and Breque, 1983; Murray et al., 2001). In the extrusion system, raw feed ingredients are exposed to the high temperature and pressure on me- chanical shear tension in the screw-barrel assembly. The feed ingredient which is extruded takes shape from the die of end of the extruder’s barrel. However, the expansion is seen while passing from the high pressure inside the barrel to the atmospheric pres- sure. This effect causes such alterations in the feed as: changes in bulk density, affected sink rate, differ- entiation of feed size, changes in feed hardness, en- durance to the water and decreased stability. For ex- ample, the diameter of the pellets changes due to the expansion effect. For this reason, these pellets, which are larger than the fsh mouths, can’t be eaten. On the other hand, sinking pellets which are not consumed ABSTRACT. In this study, the effects of expansion control devices (ECD) used in the production of extruded fsh feed pellets were investigated. Five types of experimental sea bass feed with different pellets diameter (3, 4, 5, 6 and 9 mm for S3, S4, S5, S6 and S9, respectively) based on commercial formulations (lower total vegetable ingredients but higher starch and protein amount in S3 feed) were produced without or with the usage of ECD during extrusion process. The pellets quality was compared based on: pellets diameter size, pellet hardness, pellet durability, sink rate, after-extruder density, after-cooler density, moisture, loss quantity measurements and physical appearance. The obtained results showed that the pellets produced with ECD had lower diameters except for S3 feeds. The sink rate, and after-extruder and after-cooler densities were higher, and loss quantity was reduced in pellets produced with ECD regardless pellets size. There were less dusty and cracked pellets in feeds produced with ECD. It can be concluded that the ECD could be successfully used in the production of extruded fsh pellets contributing to lower production costs. Received: 10 November 2016 Revised: 23 March 2017 Accepted: 10 June 2017 1 Corresponding author: e-mail: ayskop@gmail.com