title: Growth and gas formation by Lactobacillus wasatchensis, a novel obligatory heterofermentative nonstarter lactic acid bacterium, in Cheddar-style cheese made using a Streptococcus thermophilus starter.
abstract: A novel slow-growing, obligatory heterofermentative, nonstarter lactic acid bacterium (NSLAB), Lactobacillus wasatchensis WDC04, was studied for growth and gas production in Cheddar-style cheese made using Streptococcus thermophilus as the starter culture. Cheesemaking trials were conducted using S. thermophilus alone or in combination with Lb. wasatchensis deliberately added to cheese milk at a level of ~10(4) cfu/mL. Resulting cheeses were ripened at 6 or 12°C. At d 1, starter streptococcal numbers were similar in both cheeses (~10(9) cfu/g) and fast-growing NSLAB lactobacilli counts were below detectable levels (<10(2) cfu/g). As expected, Lactobacillus wasatchensis counts were 3×10(5) cfu/g in cheeses inoculated with this bacterium and below enumeration limits in the control cheese. Starter streptococci decreased over time at both storage temperatures but declined more rapidly at 12°C, especially in cheese also containing Lb. wasatchensis. Populations of fast-growing NSLAB and the slow-growing Lb. wasatchensis reached 5×10(7) and 2×10(8) cfu/g, respectively, after 16 wk of storage at 12°C. Growth of NSLAB coincided with a reduction in galactose concentration in the cheese from 0.6 to 0.1%. Levels of galactose at 6°C had similar decrease. Gas formation and textural defects were only observed in cheese with added Lb. wasatchensis ripened at 12°C. Use of S. thermophilus as starter culture resulted in galactose accumulation that Lb. wasatchensis can use to produce CO2, which contributes to late gas blowing in Cheddar-style cheeses, especially when the cheese is ripened at elevated temperature.
authors.affiliation: Western Dairy Center, Department of Nutrition, Dietetics, and Food Sciences, Utah State University, Logan 84322-8700.
authors.forename: Fatih
authors.initials: F
authors.lastname: Ortakci
authors.affiliation: Western Dairy Center, Department of Nutrition, Dietetics, and Food Sciences, Utah State University, Logan 84322-8700. Electronic address: Jeff.Broadbent@usu.edu.
authors.forename: Jeffery R
authors.initials: JR
authors.lastname: Broadbent
authors.affiliation: Western Dairy Center, Department of Nutrition, Dietetics, and Food Sciences, Utah State University, Logan 84322-8700; Microbiology Department, Weber State University, Ogden, UT 84408-2506.
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Oberg
authors.affiliation: Western Dairy Center, Department of Nutrition, Dietetics, and Food Sciences, Utah State University, Logan 84322-8700. Electronic address: Donald.McMahon@usu.edu.
authors.forename: Donald J
authors.initials: DJ
authors.lastname: McMahon
mesh_terms: D000818:Animals; D002611:Cheese / Q000382:microbiology*; D015169:Colony Count, Microbial; D005285:Fermentation; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D007778:Lactobacillus / Q000254:growth & development*; D008892:Milk / Q000382:microbiology; D048249:Streptococcus thermophilus / Q000254:growth & development*; D013696:Temperature
keywords: Streptococcus thermophilus; cheese; galactose; late blowing; nonstarter lactic acid bacteria