The microflora of Tilsit cheese. Part 2. Development of a surface smear starter culture

Abstract

Single strains of bacteria isolated from the surface of commercial Tilsit cheeses were screened for their ability to produce typical Tilsit flavour and colour and for fast growth in milk. Three milk based model systems were developed for screening. Shake liquid milk cultures were suitable to determine production of colour and volatile flavour compounds. Milk agar plates were used to study synergistic and antagonistic effects between isolates. With mini cheeses in centrifuge bottles, cheese conditions were simulated under sterile conditions. Volatile aroma production and pigmentation of the surface flora were studied with this system. Additional growth studies in other growth media with various combinations of strains revealed some of the possible roles of surface bacteria. Brevibacfen'um linens promoted growth of yellow coryneform bacteria. A pigmented Arthrobacter strain was responsible for the production of a yellow coloured watersoluble pigment, a precursor for the typical red-brown colour of Tilsit cheese. In mixed culture with pigmented or non-pigmented strains of B. linens, the yellow colour turned into red-brown. A proteolytic Staphylococcus strain seemed to be important for the initiation of surface starter growth. Staphylococci showed fast growth at pH 5.5 and below. They also promoted growth of the yellow Arthrobacter strain.Based on these results, a defined surface starter was developed consisting of 5 strains. The yeast Debaryomyces hansenii was used for deacidification of the cheese rind. A combination of a non-pigmented, proteolytic B. linens, a yellow Arhrobacter strain, a cream-coloured coryneform bacterium, and a proteolytic Staphylococcus sciuri were used for cheese ripening. Experimental cheeses were produced on a 10 kg scale. The defined starter grew fast on the cheese surfaces, and produced the typical taste and flavour and colour of Tilsit cheese.

Commercial Ripening Starter Microorganisms Inoculated into Cheese Milk Do Not Successfully Establish Themselves in the Resident Microbial Ripening Consortia of a South German Red Smear Cheese

“…For this purpose, defined and optimized smear starter cultures have to be composed of strains that are able to compete with well-adapted in-house consortia in order to establish successfully on the cheese surface (1,2). Certain strains may not be suitable for smear cheese ripening, while others have been used successfully in defined cultures of some cheese types (1,4,6). Furthermore, a commercial culture has to be applied in an optimized way.…”

“…It would also be an interesting alternative to directly use the house microflora as a smear starter culture to boost its positive effect. Nevertheless, since undesired organisms such as L. monocytogenes can become part of the in-house microbial ripening consortium and persist in the dairy by this back-slopping cycle, the long-term aim should be to completely avoid the old-young smearing process and, instead, to produce cheese merely by using optimized, defined ripening starter cultures (1,4,6) applied in an effective way as soon as such starters become available. Since food safety has top priority, the development of suitable, defined surface starter cultures is urgent.…”

The Presence of Peptidoglycan O -Acetyltransferase in Various Staphylococcal Species Correlates with Lysozyme Resistance and Pathogenicity

“…S. xylosus (5,35,48), S. pulvereri (5), S. succinus (43), S. pasteuri (43), and S. equorum (5,35) were found to be dominant on traditional fermented meat and on the surface of ripened cheese but have also been isolated from goat milk (48). For more than 50 years, nonpathogenic staphylococci, such as S. carnosus (8,45,46,54), S. equorum (10,42,45), S. sciuri (7,44), S. xylosus (25,36,45), and S. pulvereri (8), have been used as starter cultures in fermentation and biopreservation of food (meat, cheese, and probiotics). Since pathogenic staphylococci colonize the host over a longer period and cause chronic infections and are exposed to all tissue bactericides that kill or inhibit the growth of microbes, they must have developed mechanisms that evade lysozyme defense.…”

Fourier-transform infrared (FT–IR) spectroscopy is a promising tool for monitoring the population dynamics of microorganisms in food stuff

“…However, the process also bears the risk of transferring unwanted or even pathogenic microorganisms such as Listeria monocytogenes onto a new batch [10]. Several attempts to use defined starter cultures, instead of undefined microbial consortia from ripened cheeses to inoculate fresh cheeses, have shown variable results with respect to flavor and quality [11,12,13,14].…”