We investigated the chemical components of red onion powder dried using the low temperature vacuum method and the inhibitory effects of solvent extracts of the dried red onion powder on the growth of HT-1080 human fibrosarcoma and HT- 29 human colon cancer cells and H2O2-induced oxidative stress. The moisture content of the dried red onion powder was 17.95%, while the vitamin C content was 96 mg/100 g and the total phenols content was 39.1 mg/mL. The inhibitory effects of acetone with methylene chloride (A+M) and methanol (MeOH) extracts of the red onion powder on the growth of HT- 1080 and HT-29 cancer cells increased in a dose dependent manner (p<0.05). The inhibitory effect was greater on the growth of HT-29 cells, while the A+M extracts had a higher inhibitory effect than the MeOH extracts. Treatment with the hexane, 85% aq. methanol, butanol and water fractions of the extract led to significant inhibition of the growth of both cancer cell lines (p<0.05). Among the fractions, the hexane and 85% aq. methanol fractions showed a greater inhibitory effect. To determine the protective effect on H2O2-induced oxidative stress, a DCFH-DA (dichlorodihydrofluorescin diacetate) assay was conducted. All fractions, including the crude extracts of dried red onion, appeared to lead to a significant reduction in the levels of intracellular reactive oxygen species (ROS), and these reductions occurred in a dose dependent fashion (p<0.05). Among the fractions, the 85% methanol fraction showed the greatest protective effect on the production of lipid peroxides.

The study was done in order to investigate the effects the red onion powder on the quality characteristics of the Korean steamed rice cake, Seolgiddok, with 3%, 6%, 9% and 12% of the red onion powder weight in control. The moisture content of the control with 0% red onion was 43.74% and it steadily decreased with the increase in powder (12%) resulting to the lowest at 37.02% for the cake. The springiness, adhesiveness and chewiness of the cake decreased according to the increase in powder content, while the hardness and cohesiveness increased together with the increase in powder content. The Hunter color value L in the chromaticity of the cake significantly decreased with the increase in powder content. The a value of the control was 2.18 and was redder with the increase in powder content, while the b value significantly increased together with the increase in powder content. The sensory characteristics of the cake such as color, flavor, taste and softness and chewiness increased along with increase in powder content. The overall taste was judged to be the best for the sample with the 9% added powder.