Product Extrusion

Cooling die RSKD-3500

The annular gap cooling die RSKD-3500 is designed for use with a twin screw extruder. By means of the so-called "High Moisture Extrusion" process, this design allows the production of vegan meat analogs with meat-like fiber structure from protein-based water-solid mixtures. Suitable raw materials are protein-containing, free-flowing materials that are transported from the upstream extruder and then textured in the annular gap cooling die. The annular gap cooling die is actively cooled by an external cooling unit.


The annular gap cooling die RSKD-3500 consists of the transfer segments 1C and 2C (Item No.1+2), four cooling die segments (Item No.3) and a protective hood for the transfer segments (Item No.4). A cleaning unit (Item No.9) is used to clean the cooling die segments. The transfer segment 1C is attached to the outlet of the twin screw extruder with screw connections.

The transfer segment 2C with a conical transition ensures the transfer of the product to the product channel of the first cooling die segment. The individual cooling die segments are connected to each other by means of tension chains. A schematic representation of the RSKD-3500 annular gap cooling die consisting of four cooling die segments is shown in Figure 1. Figure 2 shows a side view of the annular gap cooling die without protective housing. It shows the individual components of the annular gap cooling die.

In the area of the cooling die segments the product is cooled down to the desired temperature. Cooling water (alternatively glycol) is pumped by an external cooling unit through the cooling channels of the cooling die core and the cooling die jacket. The use of a cooling unit with a capacity of 30 kW is recommended.

After leaving the annular gap cooling die unit (Figure 3), the product can be further processed. The protective hoods around the assembly of the transfer segments and the annular gap cooling die unit provide protection against burns, as the latter heats up to 130 °C.

The throughput of the annular gap cooling die unit is up to 500 kg/h. The throughput depends on the following parameters: extruder type, product composition, product behavior, temperature of the protein-water mixture and the desired product structure. Experience has shown that the product temperature at the inlet to the annular gap cooling die unit should be between 110 °C - 130 °C. The resulting outlet temperatures from the annular gap cooling die unit, depending on the cooling settings, are in the range of 60 °C to 90 °C. Too high product temperatures (>100 °C) at the exit from the annular gap cooling die unit lead to product expansion.

It should be noted that the performance and functionality of the RSKD-3500 is highly dependent on the formulation and extrusion parameters. Throughputs of 500 kg/h can be achieved, for example, with recipe mixtures based on 36 % soy protein (e.g. ALPHA® 8 IP, Solae, LLC, US) with 63 % water.


Spec sheet
segment length 550 mm
Materials in contact with the product 1.4404
Tension chain holder
Plastic centering device for aligning the segments
Removable protective hood
4x coolant connection internal thread ¾”
Frames with height adjustable swivel castors +/- 40 mm (4x)
Surfaces in contact with the product are electropolished
Connection of the individual segments via quick clamping chain
Center height (distance floor- product channel center) 1100 mm
Material frame & protective hood 1.4301
Product channel approx. 350 mm x 10 mm
Product cross section approx. 3500 mm²

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