Protein Value Of DDGS: A Complex Problem
German researchers studied the effects of raw material use and production processes on the quality of soluble distiller's grains (DDGS), a by-product of ethanol production in cereals.
DDGS is used as a source of protein for the production of animals. Like the crude protein (CP) content, the degradability and digestibility of CP and amino acid (AA) are predetermined by the raw material particles, but are also affected to a considerable extent by the production process. A review of researchers from the University of Bonn in Germany and the Japan Animal Feed Science and Technology Press highlighted the steps that may affect the value of DDGS proteins during production.
Effect of feed processing steps
The thermal effects of the DDGS drying process are most often discussed. During heating, AA can undergo a series of chemical reactions that result in reduced or reduced digestibility of AA. To assess the effect of calories on the quality of DDGS proteins, measuring color variables, acidic detergent insoluble N and AA levels have been applied, although all of these methods have some limitations. In addition to drying, a further processing step that may affect the value of the DDGS protein is high temperature application prior to drying or mixing the product stream. Yeast proteins contribute to DDGS proteins, but the actual number estimates vary widely. Although the effects of the overview and their underlying principles are known, their systematic investigation is hampered by the complex nature of the production process.
The production process is complicated
In this review, several possible effects of ethanol production on the value of DDGS proteins are listed. The basic chemical, biological and technical principles of these effects are known. However, the production process is complex and the effects may be additive or interactive, making it difficult to quantify the results of protein values on a general basis. For example, the Maillard reaction process is affected not only by temperature but also by duration, water activity and pH (Mauron, 1990). Targeted studies to quantify the effects of individual processing variables on DDGS protein values may only be performed on a laboratory scale. Producers and users may need to regularly monitor the value of DDGS proteins, but this is not as easy as assessing chemical composition.
Greater variability, better standardization
Researchers have addressed the ongoing development of ethanol production processes and the introduction of new technologies, such as the hydrolysis of raw starch and the fractionation of grain or distiller's grains discussed above, for example, fiber or oil removal (Berger and Singh, 2010; Rosentrater et al., 2012). This leads to a diversification of the distiller's grains by-products and may result in greater changes in the chemical composition and protein value of DDGS (Martinez-Amezcua et al., 2007). On the other hand, it may contribute to better standardization and tightly defined products within companies and factories.