TO GRIND OR NOT TO GRIND

Grinding the soybean prior to extrusion is the only way to go. The pros to running ground soy:

1) Reduced energy consumption – when extruding whole soy, you are turning the extruder into a grinder and extruder, which increases the energy consumption drastically.

2) Increased production – by grinding or rolling the soy, the amount of restriction needed to properly extrude the product can be reduced, which allows for up to 8% to 10% increased capacity.

3) Reduced wear to parts (internal and external) of the extruder – there is a significant reduction of wear to the inlet chamber and inlet screws. Anyone who has dealt with the transport of whole soybeans can tell you how abrasive they are (elevators, augers, head pulleys, etc.)

4) Finer, more consistent finished product – this makes for better mixing with other ingredients in a finished formulation. It also makes the cooling process easier, especially in hot weather.

5) Increased quality of extrusion as it relates to urease and trypsin inhibitor removal – because the soy has been ground, the smaller particle size exposes more of the soy to the heat and pressure needed to assure a good quality finished product.

When extruding whole soybeans, you will notice a wide variation in the particle size of the finished product with the larger particles sometimes being undercooked.

The only con is the additional expenditure for a grinder or roller mill. This however is offset by the savings in wear parts. The additional energy consumption is offset by reduced consumption at the extruder and increased production capacity. The savings in wear parts and increased product quality make up the rest.

The pros far outweigh the cons making pre-grinding or raw soybeans the best option when extruding.