Linseed-Sunflower Meal Co-extrudate as a Functional Additive for Animal Feed – extrusion Optimization

Abstract

The presented study shows a simple way for optimiza tion of extrusion process, which was used for deterioration of cyanogenic glycosides – antinutritive components of linseed, with minimum damage of essential Alpha-Linolenic Ac id (ALA) at the same time. Extrusion of the material was done on a laboratory single screw extruder. Content of Hydrogen cyanide (HCN) as a measurement of cyanogen ic glycosides in produced co- extrudate and fatty acid composition were determine d, together with basic chemical analyses, which were done in accordance with AOAC m ethods. Statistical analysis showed that HCN content in the product was the most depend ent (P= 0.0002) on quadratic influence of moisture content of starting material. The highest HCN content (126 mg kg -1 ) was measured at the lowest moisture content (7%) an d the lowest screw speed (240 rpm). Low moisture content caused weak volatilization of HCN along with the evaporating water, which was intensified with higher values of moisture content. However, increase in moisture content from 11.5 to 16% slightly increase d the amount of present HCN, due to the lower material viscosity. Extrusion process cau sed some changes in fatty acid composition, but even the highest degradation of AL A did not exceed 4%. Linear and quadratic influence of moisture content on ALA redu ction was significant (P< 0.05), as well as quadratic influence of screw speed. Specifi c attention has to be paid to selecting appropriate levels of screw speed and moisture cont ent of the material which contains linseed, in order to achieve both detoxification of linseed and preservation of essential fatty acids. Keywords : Cyanogenic Glycosides, Essential fatty acids, Ext rusion, Linseed, Sunflower meal.