Value-added application of bourbon spent grain and proso millet for high-fiber extruded product
Abstract
Bourbon is an important export for the US, especially in the state of Kentucky, which accounts for 95% of global production. The disposal of the main byproduct of bourbon distilling is a major problem for the industry. Distiller‘s spent grain (DSG) produced contains insoluble and soluble fibers and protein, making it an attractive option as a health-promoting functional ingredient in food production. The objective of this research was to determine the DSG properties needed for the development of high-fiber extruded products with millet as the base-starch ingredient. Samples were produced using a co-rotating twin-screw extruder. A two-way factorial design was used to test the effect of DSG particle size (180, 300, and 500 μm) and addition levels (5%, 10%, and 15%) on some physico-functional properties of the extrudates, such as specific mechanical energy, water solubility index, water absorption index, radial expansion ratio, fracturability, hardness, porosity, degree of gelatinization, and pasting properties. In general, higher DSG addition levels resulted in decreased radial expansion and porosity, and created harder, bulkier, and darker color products. However, samples produced with medium particle size DSG (300 µm) at 5% addition level saw no significant decrease in expansion or hardness compared to the control (0% DSG). Similarly, at 10% DSG addition level and coarse (500 µm) particle size, there was no significant difference in porosity compared to the control group. This study shows that optimized particle size and DSG addition level allow the incorporation of bourbon spent grain into an extruded-expanded product without significant loss of attributes but with higher dietary fiber content..
