Soybean, a strategic product in the world, has eight main varieties and is used in oil industry and makes up 5 percent of whole oil beans. Several methods are used for the processing of soybeans such as autoclave, browning, frying, micronizing, dry and wet extrusion, pelleting and ... . each of the methods mentioned above have different effectson the nutritinal value of soybean. Using extrusion for processing of raw soybean increases the nutritional value, metabolizable energy, protein digestibility, linoleic acid, vitamin E, lystyn and anti-nutritional substances.

Extrusion Cooking:

Extrusion is a short time and high-temprature thermal processes in which protein digestibility is increased due to denaturation and minimal thermal damage occure. During extrusion cooking cells containing oil burst and make the oil available for animal. Control of critical factors during the process of exrusion cooking is the sign of a qualified process.( over process & under process). Therefore the mechanical process of insulation cannot be compared with extrusion. Because of anti-nutritional substances in raw soybean seeds, it cannot be used in animal feed. The raw soybeans contain anti-nutritional factors including anti-trypsin, kimotrypsin, phythomaglotin (lystyn), ureaze, lipaze and allergic factors of lipaze and lipoxigenaze.

Extrusion of soybeans cuases:

1 - The reduction of anti-trypsin in soybean seeds.anti-trypsin is a proteaze that is harmful to humans and most animals. The anti-nutritional factors decreases to 85 percents during thermal processes of extrusion. Anti-trypsin destruction depends on the moisture entering the system, the moisture of of soybean, temprature and duration of heating during the process of extrusion (optimum moisture of 9-11% and optimum temperature of 150-160% is predicted).

2 - The release of of oil and α-tocopherol to space between cells in the extruded soybean. Extruded soybean includs high levels of tocopherol and lystyn (4%) which is stored as anti-oxidant. Extrusion makes vitamin E available to animals along with oil.

3 - Undegraded Intake Protein (UIP), increased palatability, high energy density and digestibility of carbohydrates in ruminants. You can use extruded soybeans up to 15 percent in livestock feed, provided that the level of calcium and magnesium of diet is increased.

4 - Increasing the apparent metabolizable energy (AME) in poultry

5 - Destruction of urease and allergic factors

6 - Increasing the digestibility of carbohydrates

7- Reduction of dust during production

8 - Reduction of Mycotoxin in the products

Soy can get the full quality assurance testing for quality control of products during the manufacturing process and product monitoring, which includes:

·        Measuring levels of anti-trypsin and urease

·        Measuring insoluble nitrogen in acid detergent

·        Lipase test: indicating increasing temperature during the production process

·        PDI Test: used to measure product durability in the water. PDI index reduces as heat increases.

·        Appearance: The color and taste of the grain is the first and simplest test. Through a good process, the color of seed should be golden-brown and the taste shouldn't be bitter.