Processing raw materials: cereals

The treatment of cereals and protein crops by extrusion cooking offers definite advantages:

–Gelatinization of starch improves digestibility of raw material carbohydrates.

Use of preconditioner with water and steam addition facilitates this gelatinization operation and greatly increases extruder efficiency.

Extrusion treatment promotes carbohydrates effectiveness in young animals or in species where amylase production is poorly developed.

–Reduction of proteins solubility

The very short time during which the product is subjected to very high temperatures does not cause a decrease in proteins digestibility due to Maillard reaction.

Extrusion causes the insolubilization of native proteins contained in protein crops and oleaginous plants. This transformation is particularly interesting for use of these raw materials in ruminants diet, since it decreases soluble nitrogen proportion (DINP) and increases the non-degradable nitrogen content in rumen (DPIA).

–Anti-nutritional factors destruction

•  90% Destruction of antitrypsic factors contained in soy and protein crops.
• Decrease in glucosinolate content of colzaseeds and meals, in cotton gossypol, in aflatoxin in peanut meals and ingredients contaminated by these molds.
• The inactivation of enzymatic systems responsible for hydrocyanic acid release from linseeds and meals, as well as those of lipases and lipoxidases present in oleaginous seeds, thus preventing the rancidity and oxidation of the oil they contain.
• Release of fat contained in the cells: increase of the metabolizable energy and fat stabilization, decrease of oil oxidation.
• Product output forming: passage in dies at extruder exit gives products various size and shapes.

Read Dr. Legoy’s article on this topic:

http://maurice.legoy.free.fr/extrusion/transformations/index.htm