Improvement of Low-fat Cheddar Cheese Through Identification and Characterization of Microbial Enzymes Responsible for the Conversion of Aromatic Amino Acids into Off-Flavor Compounds in Cheese
Dr. Jeffery R. Broadbent, Utah State University
Dr. Bart C. Weimer, Utah State University
Development of off flavors is a significant problem in low-fat Cheddar cheese. Compounds associated with unclean, medicinal or utensil, and floral or rosy off flavors may arise via microbial catabolism of aromatic amino acids. Starter, adjunct, and nonstarter lactic acid bacteria may catabolize aromatic amino acids under conditions found in Cheddar cheese, and pathways involved in these reactions can facilitate the production of off flavor compounds. This project will investigate the contribution of metabolic cross-feeding between starter, adjunct, and nonstarter bacteria to the production or removal of aromatic off flavor compounds, the specific roles for selected enzymes in the production of these compounds, and confirm that these enzymes and pathways are functional in low-fat Cheddar cheese. Results from the project will facilitate industry efforts to understand and control flavor development in low-fat Cheddar cheese by providing new strategies, based on enzyme assays, gene probes, or recombinant DNA technology, that can be used to identify or develop starter systems which avoid or reduce development of utensil, medicinal, unclean, putrid, and floral off flavors in low-fat Cheddar cheese.
Gummalla, S. M. Drake, S. Rankin, and J. R. Broadbent. Overexpression of Lactobacillus casei D-hydroxyisocaproate dehydrogenase: effects on cheese volatile chemistry and sensory properties. Manuscript in preparation.
Gummalla, S. and J. R. Broadbent. 2001. Tyrosine and phenylalanine catabolism by Lactobacillus cheese flavor adjuncts. J. Dairy Sci. (in press).
Gummalla, S., and J.R. Broadbent. 1999. Tryptophan catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts. J. Dairy Sci. 82:2070-2077.
Steele, J.L., M.E. Johnson, J.R. Broadbent, and B.C. Weimer. 1998. Starter culture attributes which affect cheese flavor development, pp. 157-170. In, Proc. LACTIC '97 conference, Which strains? For which products?
Gao, S., D-H. Oh, J.R. Broadbent, M.E. Johnson, B.C. Weimer, and J.L. Steele. 1997. Aromatic amino acid catabolism by lactococci. Lait 77:371-381.
Broadbent, J., C. Brennand, M. Johnson, J. Steele, M. Strickland, and B. Weimer. 1997. Starter contribution to reduced fat Cheddar. Dairy Ind. Int. 62 (2):35-39.
Gummalla, S. 1998. Tryptophan catabolism in Lactobacillus spp. MS thesis, Utah State University.
Broadbent, J.R. Role of lactic acid bacteria in cheese flavor development. Invited oral presentation for special ADSA pre-meeting workshop on the basics of flavor development in cheese. Sponsored by the American Dairy Science Association and Rhodia, Inc. July 24, Baltimore, MD.
Broadbent, J.R. and S. Gummalla. Tryptophan Catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts. Poster presentation at the 6th International Symposium on Lactic Acid Bacteria Genetics, Metabolism, and Applications. September 19-23, Veldhoven, The Netherlands.
Broadbent, J.R. Cheese curing and flavor development. Invited oral presentation for the 15th Cheese Making Short Course. February 9-11, Utah State University, Logan.
Broadbent, J.R. 1998. How starter bacteria direct cheese flavor development. Invited oral presentation for the 13th Biennial Cheese Conference. Aug. 10-12, Utah State University, Logan.
Broadbent, J.R. 1998. Cheese curing and flavor development. Invited oral presentation for the 14th Cheese Making Short Course. March 26-28, Utah State University, Logan.