Doctor of Philosophy, The Ohio State University, 2005, Food Science and Nutrition

Propionibacterium freudenriechii is utilized in Swiss cheese starter cultures. Its carbon dioxide production is responsible for the development of the eyes associated with Swiss cheese. The bacteria must endure low storage temperatures during ripening. Bacteria are capable of synthesizing compatible solutes in response to stress. The primary focus of the present study was to determine the growth capabilities of P. freudenreichii strains in the presence of exogenous glycine betaine, proline, and glutamate at low temperatures and evaluate the effects of storage temperature on eye formation in Swiss cheese manufactured with these strains. Four P. freudenreichii strains were grown in chemically defined media with exogenous glycine betaine, proline, or glutamate, anaerobically incubated at 30, 22, 10, 7.2, and 4°C, and spectrophometrically monitored to determine growth capabilities. Strains capable of growing at 7.2 and 4°C were characterized as cold-tolerant (P728 and P873) and strains not able to grow at these temperatures were characterized as cold-sensitive (P843 and P572). Compatible solute transport was assessed using 14C-labeled amino acids. All strains transported proline most abundantly. These strains were also subjected to several freeze-thaw cycles to determine if effects of glycine betaine at temperatures below refrigeration. There was a difference between all strains suggesting that freeze-thaw tolerance is strain dependent in propionibacteria. Swiss cheese was manufactured with a cold-tolerant strain (P873), a cold-sensitive strain (P572) and an intermediate strain (P196). Cheese blocks differed in cool ripening storage and samples taken at days 0, 30, 60, and 90. The twenty most common amino acids were quantified during each ripening phase. Differences were observed among each strain with differences observed between strains after 90 days at 4°C and 7.2°C. Digital images of day 60 and 90 samples were analyzed for splits. More eyes and splits were seen in c (open full item for complete abstract)

Committee: W. Harper (Advisor) Subjects: