Thermal processing of soybean meal for poultry nutrition, Understanding its importance.
Possessing adequate knowledge about the nutritional value of ingredients is a key point when it comes to the formulation of monogastric animal diets. Soybean meal is the main protein source with the highest intake levels within this type of diets. In this regard, Rostagno et al. (2017) recommend up to 35% inclusion of the ingredient in broiler formulations. Therefore, quality control of this raw material is essential for ensuring good animal performance levels in the field.
Raw soybeans contain several anti-nutritional factors, such as protease inhibitors and lectins, as well as allergenic factors such as glycinin and beta conglycinin. These are inactivated through heat treatment during processing. On the other hand, there are other heat-resistant compounds such as: oligosaccharides, non-starch polysaccharides and phytate. (Medic et al., 2014).
Analytical methods to evaluate soybean meal quality
Currently the industry employs two techniques to assess if the grain’s thermal processing has been adequate. These two techniques have become widely adopted as they are easy to execute and hold low laboratory costs. These two tests are known as: solubility in KOH 0.02% and the urease activity test.
Solubility in KOH
Solubility in KOH evaluates the quality of processing and inactivation of anti-nutritional factors. Values above 75% of protein solubility indicate a higher biological quality of protein and better amino acid utilization by the gastrointestinal tract.
When values are below the desirable levels, this indicates that there has been thermal super processing. Causing protein denaturation reactions, complexation of amino acids and a reduction of sugars (Maillard reaction). Consequently, the product loses nutritional quality due to a lower availability of amino acids (Heidenreich, 2000).
Urease activity test
The urease activity test or index is an indirect measuring tool, that indicates if there has been thermal subprocessing through the determination of pH variations.
The higher the value recorded in the test, the greater the urease activity present in the sample.
Raw soybeans should present pH variations that range from 2.0 and 2.5 (Butolo, 2002). After thermal processing toasted soybean meal should have a pH variation within a 0.05 and 0.25 range, according to mapa (1993).
Anti-nutritional factors that impact performance and productivity
Bowman-...
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