New Extrudates with LDI: Multi-Color and Multi-Texture
Liquid direct injection (LDI) is a further development of the TURBO technology patented by Schaaf, which allows the production of attractive direct expanded products by providing them multiple colours and textures.
In Liquid direct injection, fluids (low viscous fluids e.g. water, vegetable oil etc.) are injected into the TURBO chamber at a pressure of 60-100 bars. Depending on the configuration of the TURBO tools, it is possible to mix the fluid homogenously or keep them as distinct layers in the extrusion dough.
For the production of multicolour extrudates, the flow of the dough in the extruder processing section is separated into two separate streams. A coloured fluid is then injected into one of the dough streams with the help of a high pressure pump. In order to prevent the re-mixing of the dough streams in the extruder, they are brought together again just before the exit of the die.
If desired, partial mixing can be achieved if the point of combination of the dough streams is moved to a point which is deeper inside the die-system. The result is an extrudate with a „marbled“ appearance.
The possibility of injecting fluid in a part of the dough stream causes simultaneously an additional effect - the injected fluid changes the dough composition of the particular dough stream. As doughs with different moisture/fat content display different expansion characteristics, one can achieve, with the help of a targeted combination or mixing of the dough stream in the extruder, multi-texture products. These products, with some areas softer/harder or fine-pored/coarse-pored, present absolutely new product concepts in the field of direct-extrusion.