Date of Graduation


Document Type


Degree Name

Master of Science in Food Science (MS)

Degree Level



Food Science


Navam Hettiarachchy

Committee Member

Young Kwon

Second Committee Member

Ruben Morawicki


Biological sciences; Angiotensin-converting enzyme; Antimicrobial; Chicken; Culture; Phenolic; Soybean


Soybean components provide health benefits to humans. Soybean hulls, a major by-product of the soybean processing industry consist of complex carbohydrates, proteins, lipids and polyphenols such as anthocyanidins, proanthocyanidins and isoflavones. The polyphenolic compounds in the hulls give them various colors such as black, brown, green, yellow or even a mottled appearance. Studies have reported different soybean varieties with varying total phenolic compounds in their seed hulls, which have antioxidant property. Phenolic extracts can be used as substitutes for synthetic antimicrobials and preservatives to assist in preventing the growth of pathogens such as Salmonella Typhimurium, E coli 0157:H7, and Campylobacter jejuni, and work as angiotensin-converting enzyme (ACE) inhibitory. In this study we: 1) Prepared phenolic extracts from four selected colored soybean varieties, 2) Determined the minimum inhibitory effects of the extracts on S. Typhimurium, E coli 0157:H7, and Campylobacter jejuni in broth cultures, 3) Evaluated the inhibitory effects of extracts on Salmonella Typhimurium, E coli, and Campylobacter jejuni attached to chicken skin, and 4) Investigated the ACE-I inhibitory activity of the soybean hull phenolic extracts. The highest phenolic content was observed in R07-1927, the darkest colored soybean hull (4.29 mg CAE/g DW), and was found to be significantly different (P <0.0001) from the conventional soybean variety, R08-4004 (1.63 mg CAE/g DW). For the antimicrobial activity of the extracts, a 3 day incubation with the phenolic extract from R07-1927 was found to produce 2 log reductions in E coli and C. jejuni counts, whereas a 6 day incubation was found to reduce S. Typhimurium and E. coli at 2 and 3 logs respectively. For the chicken skin study black soybean hull extract alone was used as it had the highest concentration of total phenolics. Log reductions of 1.39 was observed for S. Typhimurium and 1.24 for E. coli when inoculated chicken skins were incubated with the extract for 6 days. The results of our study showed that soybean hull extracts may be used to reduce foodborne bacterial pathogens. The preliminary study showed that the ACE-I inhibitory activity for the R07-1927 (black) phenolic extract was 52% while the R08- 4004 (yellow) extract showed 21%.