Influence of various methods of processing soybeans on protein digestibility and reduction of nitrogen deposits in the natural environment – a review

Abstract

Soybean meal (SBM) is a significant source of protein for poultry due to its high concentration of protein and amino acids profile. The primary objective of SBM processing is the reduction and deactivation of anti-nutritional factors (ANFs) to enhance nutrient digestibility. However, eliminating ANFs does not necessarily correlate with increased protein and amino acid content. Several processing methods, such as soaking, cooking, and commercial techniques, improve SBM protein digestibility. To sustain feeding qualities, soybeans must undergo heating to remove inherent chemicals that interfering with poultry digestion. However, both under and over-processing can impair meal digestibility. Extrusion heating significantly contributes to protein and starch digestibility while reducing certain ANFs. Thermomechanical and enzyme-assisted procedures reduce heat-resistant proteins more efficiently than extraction methods, producing soy protein concentrate (SPC) and fermentation. These techniques reduce ANFs in SBM, activating digestive enzymes and alleviating digestive tract pressure, leading to decreased endogenous protein deficits. Exogenous enzyme supplementation is a biotechnological approach for enhancing the nutritional content of SBM and certain other protein-rich products. However, different processing methods not only affect protein digestibility but also impact poultry production, gastrointestinal health, and the environment due to higher nitrogen excrement. Ammonia (NH3) emissions, are a significant environmental concern in chicken farming, resulting from uric acid production during protein consumption. It has a negative impact on the environment and the health of birds/humans. This review investigates the impact of several processing techniques on the digestibility of SBM protein and the reduction of N2 regarding one health concept. Future research should focus on identifying optimal processing methods maximizing protein digestibility while minimizing environmental nitrogen impacts.