Lactobacillus helveticus
Andrea Cascio

Lactobacillus helveticus (Lb. helveticus) is non-motile, gram positive, non spore forming, rod shaped, micro-aerophilic, and thermophilic. Since this bacterium is thermophilic, the optimum growth temperature is between 39 and 50 degrees Celsius, but it can survive at higher temperatures. It should not be kept at temperatures lower than 20 degrees Celsius because this can lead to deterioration and production of spoilage bacteria. It is also homofermentative, which means that lactic acid is the principal metabolite and carbon dioxide and flavor compounds are not produced during fermentation.

Lactic acid bacteria, such as Lb. helveticus, are found in cheese milk. The name helveticus comes from the Latin word Helvetia which means Switzerland. It was given this name because it is used in the production of Swiss cheese. The purpose of these cultures is to develop acid and cause ripening. As the fermentation process continues, more and more acid is produced by the lactic acid bacteria. This lactic acid is necessary for the cheese flavor, texture, and safety. The acid also controls the moisture level through syneresis and causes coagulation, which is faster the lower the pH gets. As a starter culture Lb. helveticus works very well for cheeses such as Parmesan, Romano, provolone, and mozzarella. As an adjunct culture, Lb. helveticus is used to produce Cheddar cheese.

Cheddar cheese has a tendency to become bitter. The Lb. helveticus is added to prevent the bitterness. Dr. Jim Steele decided to identify the property of the Lb. helveticus that reduces the bitter taste to quicken the cheese making process. Slowly, he and his team knocked out the genes that were associated with the enzymes they suspected of smoothing out the flavor of the Cheddar. It took more than ten years, but they were finally able to identify the gene they were looking for. They are currently seeking a patent. There are people who do not like Steele’s idea. Bill Schlinsog says, “Cheesemaking is an art, and you lose something - a quality - when you try to take to take shortcuts.” He is convinced that cheese connoisseurs would notice the difference.

The flavor of cheese is developed by the lysis of cells. The lysis of cells provides the aminopeptidase required to hydrolyze peptides. This proteolysis, by the starter cultures, and carbohydrate metabolism contribute to the flavor, texture and aroma of the cheese.

References:

Aminopeptidase activity of Lactobacillus helveticus after high hydrostatic pressure treatment
http://ift.confex.com/ift/2002/techprogram/paper_13828.htm

Better cheddar: UW scientist finds enzyme to cut bitter taste
http://www.jsonline.com/news/gen/mar03/124715.asp

Effectiveness of Chemometric Techniques in Discrimination of Lactobacillus helveticus Biotypes from Natural Dairy Starter Cultures on the Basis of Phenotypic Characteristics
http://aem.asm.org/cgi/content/full/65/4/1450

Production of Pyroglutamic Acid by Thermophilic Lactic Acid Bacteria in Hard-cooked Mini-Cheeses
http://www.dairyscience.org/cgi/content/full/85/10/2489

Proteolysis on Reggianito Argentino Cheeses Manufactured with Natural Whey Cultures and Selected Strains of Lactobacillus helveticus
www.dairy-science.org/cgi/reprint/86/12/3831

Section D: Acidification and Coagulation
http://www.foodsci.uoguelph.ca/cheese/sectiond.htm

Use of RAPD and 16S rDNA sequencing for the study of Lactobacillus population dynamics in natural whey culture http://www.blackwell-synergy.com/links/doi/10.1046/j.1472-765X.1997.00061.x/abs

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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