Design Of SPJ-40 Twin-Screw Extruder And Its Application To Swine Blood Protein Modification

Extrusion technique is an integral high technology of conveying, mixing, compression, sheared heating, steamed sterilization, enzymatic inactivation, expansion and shaping. It has been widely used in food processing for many years. However, the experimentally adjustable extruder, which can regulate many parameters and optimize screw combination, is scarce in our country.Swine blood is nutritive and the potential of the resources is quite abundant. Since the serious shortage of mankind protein resources, developing swine blood is a promising work. However, the hemocyte of the swine blood cells belongs to horny protein and is hardly digested and assimilated for animals. So, it is the key technique for process swine blood to seek for effective ways in order to improve digest rate and meliorating the taste of blood powder.Based on the above facts, the main aim of this work is to design an extruder which can be adjustable in many aspects. The sample extruder was successfully manufactured and was applied to swine blood processing. The results of the work were as follows:1.The diameter of the combination screw extruder was 40mm,the shape of the tooth profile was parabolic curve, the screw pitch was 30 mm, the thickness of the tooth tip was 3.5mm, the screw pitch was 20 mm, the thickness of the tooth tip was 2.45 mm, the screw pitch was15 mm, the thickness of the tooth tip was 2 mm.2. The 38CrMoAl steel was chosen as the material of the involute spline axis and was experienced quenching and tempering treatment together with cold forging treatment to meet the anti-twisted requirement and to ensure the miniaturized size of the design requirement. The specification of the axis was that the pitch diameter was 21 mm with 21 gear teeth and a modulus of 1 mm.3. Six kinds of different functional screws were combined to convey, mix, shear, medium and heavy press to the material. It was easy to assemble the screws to meet the requirement of processing various foodstuff and therefore achieving the regulation of the main parameters such as screw length, rotation direction.4. Wall thickness of the extruder was defined as 8mm.5. The home-made SPJ-40 co-rotating twin-screw extruder was employed to study the expansion properties of swine blood. The results showed that the three factors, namely extrusion temperature, screw speed and the moisture of raw material have great influence to the digestible protein of the swine blood powder. Their influence order was extrusion temperature > screw speed > the moisture of raw material. Their optimum values were 160℃~165℃, 358rpm and 18%, respectively. The content of digestible crude protein and pepsin of the resulting powder were 0.77g/g and 91.24%. The edibility of the powder was greatly improved through extruding processing.