Antibacterial and antioxidant properties of sorghum distillery residue

The alcohol extract (AE), cold water extract (CWE) and hot water extract (HWE) of sorghum distillery residues (SDR, also referred to in the literature as sorghum spirits lees, sorghum liquor waste, or grain sorghum dried distillers grains) were found to effectively inhibit the growth of Bacillus cereus, Escherichia coli O157 : H7, Salmonella spp. and Staphylococcus aureus. As the concentration of alcohol or water extracts increased to 6 mg/mL, no survival was detected. All extracts of SDR were evaluated for their antibacterial activity, radical-scavenging activity, reducing capacity, ferrous ion-chelating activity, total antioxidant activity and hydrogen peroxide scavenging activity. At a concentration of 75 μg/mL, the reducing capacities of the AE and HWE were not significantly different from BHA or Trolox (p > 0.05). The ferrous ion-chelating activities of AE and HWE were higher than that of citrate. Total antioxidant activity increased as concentrations of AE, CWE, and HWE increased, while AE and HWE showed higher total antioxidant activities than CWE. The results indicate that SDR alcohol or water extracts have antibacterial activity and antioxidant properties. They could be used as a source of antioxidant and antimicrobial ingredients in the food industry.