Abstract #475

# 475
Advances in nonstarter microbiology related to gassy defect in cheese .
C. Oberg*1, 1Weber State University, Ogden, UT.

Gas formation or gassy defect in aging cheese continues to be a concern in the dairy industry. This defect is manifest by slits or cracks in the cheese body and/or “blown wrappers” in cheeses aged longer than 3 mo, and tends to be sporadic and recurrent. These slits, cracks, and voids are not usually evident until cheese is graded unless cheese packaging becomes loose. Over the years, a long list of microbial culprits has been assembled, but with limited evidence concerning their continuing role in causing gassy defect. In Cheddar cheese, nonstarter lactic acid bacteria (NSLAB) populate the cheese in the latter stages of ripening, and are sometimes associated with undesirable flavors and textures, including gas production. Because enumeration and identification of NSLAB has generally been restricted to species forming easily observed colonies within 2 d at 30 or 37°C on MRS, slow growing lactobacilli species have been overlooked in past attempts to identify the cause of gas and textural defects in aging cheese. A new Lactobacillus species, Lactobacillus wasatchensis, was recently isolated using prolonged low temperature incubation from a sample of gas-blown Cheddar cheese. Genomic analysis, metabolic characterization, cheese trials, and survey data strongly indicates this organism is a primary cause of late gas defect. Recent studies have also shown several other Lactobacillus species to produce gas in culture studies and experimental cheese batches, especially under specific conditions. The presence of Lb. wasatchensis, and other lactobacilli, in commercial Cheddar cheese could mean the possibility of cheese becoming blown or split during aging, resulting in downgraded cheese. Strategies for detecting and enumerating Lb. wasatchensis, and other gas-producing LAB, along with best practices to decrease late gassy defect in aging cheese will be discussed.

Key Words: gassy defect, cheese, non-starter lactic acid bacteria

Speaker Bio

A native of Oregon, Craig J. Oberg graduated from Weber State University in 1979 and received his Ph.D. at Utah State University in 1985. He then joined the Department of Microbiology at Weber, serving for 21 years as department chair. Designated Brady Presidential Distinguished Professor of Microbiology in 2006, Dr. Oberg has received the John S. Hinckley Fellow (1998), the Alumni Association’s H. Aldous Dixon Award (1999) and the Spencer L. Seager Distinguished Teaching Award (2001). He was also the Cortez Honors Professor (2000) and the College of Science Endowed Scholar (2004-07). He has published more than eighty articles, co-authored two book chapters, delivered nearly 200 scientific presentations, received several patents, and edited a book reconciling science and religion.
His eclectic interests have led him to such diverse projects as a book and honors course on fly-fishing, a photographic essay on the microbiology of Yellowstone National Park’s thermal features, an interdisciplinary course on disease and history, and, currently, a book about pasta filata cheese with Dr. Donald McMahon. In addition to all of this, Professor Oberg has devoted considerable energy to service both on campus and in the community, including his current assignment as NCAA Faculty Representative. He has twice served as president of WSU’s Faculty Senate, president of the Utah Academy of Sciences, Arts, and Letters, and of the Intermountain Branch of the American Society for Microbiology.