Ultrasound pretreatment of wheat dried distiller’s grain (DDG) for extraction of phenolic compounds

Wheat Dried distiller’s grain (DDG), a coproduct from the ethanol production process, is rich in potentially health-promoting phenolic compounds. In the extraction of phenolic compounds from DDG, the DDG cell wall is an important barrier for mass transfer from the inside to the outside of the cell. The effect of high-power ultrasound pretreatment on destruction of DDG cell walls and extraction yield and rate was investigated. Direct sonication by an ultrasound probe horn at 24 kHz was applied and factors such as ultrasound power and treatment time were investigated. The method of nitrogen (N2) adsorption at 77 K was used as a means to determine and compare the changes in physical properties (specific surface area, pore volume and pore size) of the treated samples at different levels of ultrasound power and treatment time. Increasing specific surface area, pore volume and pore size caused by ultrasonic treatment implied development of new or larger pores and damaged cell walls. Also, it was observed that the ultrasound pretreatment of DDG particles increased the extraction yield and rate of phenolic compounds from DDG by 14.29%. Among tested ultrasound conditions, 100% ultrasound power for 30 s was evaluated as the best pretreatment condition.