Effect of drying conditions and level of condensed distillers solubles on protein quality of wheat distillers dried grain with solubles

Abstract

Reduced protein quality is one of the concerns currently confronting the supply and utilization of wheat DDGS as an animal feed ingredient. This study assessed protein quality of wheat DDGS, expressed as ADICP and lysine content, by blending WDGS with varying CDS levels and drying using heated air, microwave, and microwave-convection methods. DDGS with higher CDS content had higher protein content values. Interactions of CDS level with drying air temperature, microwave power, and microwave-convection settings had significant effect (p < 0.05) on average ADICP and lysine contents. Higher ADICP and lower lysine contents were observed when samples, at varying CDS, were dried at higher temperature, microwave power, and microwave convection settings. Significant differences observed in the color parameters of microwave- and microwave-convection dried samples were mainly due to CDS level. Interaction between drying air temperature and CDS level had a significant effect on the color of forced air convection-dried DDGS samples. Linear correlations showed lighter colored DDGS samples tend to have higher lysine and lower ADICP content, particularly for samples with higher CDS content and dried under forced air convection. Negative linear correlations between ADICP and lysine content were also found in samples with higher CDS content.