Do I Have to Dehull Soybeans Prior to Extrusion?
Once in a while, we are asked by our soy processing customers or by prospects that are interested in establishing a soybean extrusion/ ExPress® (Extrusion-Pressing) meal plant about the necessity of investing in a dehulling system.
In my personal opinion, when it comes to dehulling, the decision is a matter of economics more than nutrition.
A soybean processor has to be able to justify the investment in a dehulling system (here), find a market for the hulls and get paid for the extra cost of producing dehulled soybeans or ExPress® soybean meal.
Soybean hulls are the by-product of decorticating (dehulling) soybeans. They are considered an excellent source of fiber for ruminant animals, such as lactating cows. Soy hulls comprise an average of 46% cellulose, 18% Hemicellulose, 2.5% oil, 12% protein, 5% ash and 2% lignin. In diets of young animals such as poultry & swine starters, dehulled soybean meal is normally recommended to control the fiber intake and allow for high energy diets to be formulated. However, hulls in extruded soybeans seem to be more tolerated by poultry and swine than hulls produced from solvent extracted soybean meal processing. As a matter of fact, almost all extruded whole soybeans fed to poultry, swine and fish are being fed whole, without dehulling, when extruded soybeans have been used in these diets.
Kansas State University was interested in comparing the protein and Ileal amino acids digestibilities of extruded-expelled (ExPress® soybean meal with and without the hulls removed to dehulled solvent extracted soybean meal for swine. Their results indicated that in regards to nutrient digestibility; both ExPress® meals produced from soybeans with or without dehulling were superior to dehulled solvent extracted soybean meal. ExPress® soybean meal produced from dehulled soybeans had slightly higher nutrients density than that produced from non-dehulled soybeans but, there were no statistical differences in the digestibility of protein and amino acids.
If the above facts are clear to you, the decision on whether or not to dehull your soybeans becomes easier.