Doctor of Philosophy (PhD)


Nutrition and Food Sciences

Document Type



At least 100 million people have leaky gut syndrome. This syndrome is associated with multiple health problems such as diabetes, celiac disease, asthma, multiple sclerosis, and inflammatory bowel disease, costing more than $3 billion per year to treat. L-Glutamine, quercetin, slippery elm bark, marshmallow root, N-acetyl-d-glucosamine (NAG), licorice root, maitake mushrooms, and zinc orotate have been reported to help treat leaky gut.

The objectives were to explore the characteristics of yogurt and culture bacteria as affected by ingredients that help treat leaky gut. In yogurt, the pH, titratable acidity, syneresis, viscosity, color, Streptococcus thermophilus, Lactobacillus bulgaricus, yeast and mold and coliform counts, and rheological characteristics were determined. The sensory study was performed on day 3 of yogurt storage. The impact of these ingredients was also assessed on the acid and bile tolerances, resistance to gastric juices and lysozyme, protease activity, and viability of culture bacteria S. thermophilus and L. bulgaricus. The intestinal barrier dysfunctions of yogurt enriched with ingredients that could help treat leaky gut were analyzed in a Caco2 cell model.

When compared with control, the incorporation of slippery elm bark into yogurts led to less (P < 0.05) syneresis. L-Glutamine increased pH and n′ values and lowered titratable acidity values. NAG incorporation resulted in higher n′ and lower titratable acidity values, whereas maitake mushroom led to lower n′ values. Incorporating quercetin increased the growth of L. bulgaricus in yogurt. Adding maitake mushrooms increased the growth of S. thermophilus but lowered apparent viscosity values, whereas quercetin decreased S. thermophilus counts in yogurt. Quercetin, and maitake mushroom impacted color attributes of yogurt. Yogurts with quercetin had the lowest sensory scores. Marshmallow root, licorice root, and slippery elm bark improved bile tolerance and acid tolerance of S. thermophilus. The application of marshmallow root, NAG, and maitake mushroom significantly increased the protease activity of S. thermophilus. Compared to the control, marshmallow root and quercetin samples had higher log counts for S. thermophilus in the simulated gastric juice and lysozyme resistance test. For L. bulgaricus, licorice root, quercetin, marshmallow root, and slippery elm bark yogurts had higher log counts than the control. The intestinal barrier functions of yogurt fortified with quercetin and marshmallow root reduced inflammation of inflammation induced Caco2 cells. In conclusion, some of the ingredients that help treat leaky gut improved yogurt and culture bacteria characteristics.



Committee Chair

Dr. Kayanush Aryana

Available for download on Saturday, June 01, 2024