Optimization of Technological Parameters of Rapeseed Cake Extrusion to Obtain a Feed Additive With Protected Protein

The objective of the study is to determine the optimal process parameters for extruding rapeseed cake partially defatted using hydrodynamic cavitation. The rapeseed cake was obtained by double pressing using an AKJP-2000 deluxe electric oil press (Akitajp, Taiwan) for cold and hot pressing at a pressing temperature of 50 °C. Spring rapeseed was grown on the Solyanskoye Agricultural Farm, a farm located in the Central Siberian Plateau, with the Rybinsk Basin (in the southern part) designated as its agricultural area. The seeds were harvested at full grain maturity (101–110 days after germination). The resulting cake was partially defatted using hydrodynamic cavitation and then extruded. The process parameters studied were extrusion temperature and cake moisture content, while the response functions were fiber content (% a.d.m.) and undigestible protein content (% of total protein). A statistical design of experiments (DSE) method was used to substantiate the optimal rapeseed cake extrusion parameters. During rapeseed cake extrusion, a decrease in fiber content and an increase in undigestible protein content were observed. Mathematical modeling of the extrusion process revealed that extrusion temperature had the primary influence on fiber content and undigestible protein content. The temperature effect, calculated as the factorial sum of squares to the total sum of squares, was 89.65 % for fiber and 87.64 % for protein, respectively. The moisture content of the extruded cake had a significantly smaller effect, with an effect of 4.74 % for fiber and 3.81 % for protein. Since the amount of rumen-undegradable protein is the key parameter for developing protein-protected feeds, the optimal parameters for rapeseed cake extrusion are a process temperature of 130 °C and a cake moisture content of 20 %. Under these parameters, the concentration of rumen-undegradable protein is at its maximum—77.39 %.