Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


School of Nutrition and Food Sciences

First Advisor

Paul W. Wilson


The primary purpose of this study was to determine if addition of pumpkin pie spice to sweet potato puree would enhance consumer acceptance of sweet potato flavored yogurt. In Phase I, the effect of fat percentage, spice percentage, and addition of sweet potato pre-fermentation and post-fermentation on consumer acceptance was examined to determine the optimum treatment preferred by consumers and the effect of each treatment variable on the fermentation process. Phase II focused on the effect of storage periods of 7, 14, and 21 days on the organoleptic qualities and chemical composition of sweet potato. Analyses showed that the percentage of spice in the treatment appeared to have an effect on pH during fermentation. Treatments containing higher percentages of spice exhibited a slower drop in pH during the fermentation process. The effect was more pronounced in treatments containing .4 percent spice. Addition of sweet potato pre-fermentation and post-fermentation impacted consumer acceptance, viscosity, and glucose and sucrose content. Consumers appeared to prefer treatments with higher percentages of spice content in which sweet potato was added pre-fermentation. In addition, treatments in which sweet potato was added pre-fermentation exhibited higher viscosity regardless of fat and spice percentage and were rated higher by consumers in evaluation of texture. Analyses of Phase II data showed that consumers preferred treatments containing 5 and 6 percent sugar and storage periods of 14 days. Percent added sugar impacted pH, titratable acidity, glucose and sucrose levels. Treatments with lower percentages of added sugar exhibited lower pH values and higher titratable acidity for all storage periods. Treatments with higher percentages of added sugar prefermentation exhibited higher glucose and sucrose levels across storage periods. Dry matter exhibited a storage effect with significant increases in dry matter after 21 days of storage. Viscosity and starch content were not impacted by sugar or storage. Future research should focus on refinement of the yogurt formula to improve the organoleptic properties of the product. Other flavor or textural enhancements such as spiced granola or pecans should be explored. Additional research to determine the nature of the spice on the fermentation process is needed.