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Prevent germination and growth by gas-forming bacteria in high-pH cheeses.

Clostridium tyrobutyricum is believed to be the major cause of the late blowing defect in high-pH cheeses such as Gouda and Edam. This defect is caused by the fermentation of lactate Lactate

A salt or ester of lactic acid (CH3CHOHCOOH). In lactates, the acidic hydrogen of the carboxyl group has been replaced by a metal or an organic radical. Lactates are optically active, with a chiral center at carbon 2.
 and the resulting production of gas and malodorous mal·o·dor·ous  
Having a bad odor; foul.

mal·odor·ous·ly adv.

 butyric acid. There are a variety of techniques for enumerating endospores of C. tyrobutyricum in milk. Most of these methods are relatively non-specific, enumerating a variety of Clostridium clostridium

Any of the rod-shaped, usually gram-positive bacteria (see gram stain) that make up the genus Clostridium. They are found in soil, water, and the intestinal tracts of humans and other animals. Some species grow only in the complete absence of oxygen.
 spp. capable of fermenting lactate and producing gas. Alternatively, qualitative methods using DNA probes are available to determine if C. tyrobutyricum is present.

Using a quantitative most-probable number method, scientists at the University of Wisconsin (Department of Food Science, 1605 Linden Dr., Madison, WI 53706) surveyed 21 pasteurized milk samples obtained from eight different cheese plants in Wisconsin. Numbers of endospores of lactate-fermenting, gas-producing Clostridium spp. never exceeded a concentration of 10 endospores/ml, but at least 1 endospore/50 ml was present in all samples.

Further evaluation of 14 milk samples showed, however, that most of these endospores were produced by Clostridium spp. other than C. tyrobutyricum. Investigators characterized 33 isolates obtained from the milk samples. Five isolates were identified as C. tyrobutyricum. Of 24 Clostridium isolates tested, all but one produced significant amounts of gas during the ripening ripening

said of meat. See curing.
 of Gouda cheese after the inoculation of high concentrations of endospores.

The most discriminating technique for differentiating among the C. tyrobutyricum isolates, as well as the other 28 non-tyrobutyricum Clostridium spp., was the gas chromatographic chro·mat·o·graph  
An instrument that produces a chromatogram.

tr.v. chro·mat·o·graphed, chro·mat·o·graph·ing, chro·mat·o·graphs
To separate and analyze by chromatography.
 analysis of cell membrane fatty acids.

It appears that low concentrations of endospores produced by lactate-fermenting, gas-producing Clostridium are present in certain milk that is used to make cheese. The majority of these endospores are not C. tyrobutyricum. But in high concentrations they may still produce deleterious amounts of gas during the ripening of high-pH cheeses. Further studies are needed to examine how cheese-ripening conditions or the centrifugation Centrifugation

A mechanical method of separating immiscible liquids or solids from liquids by the application of centrifugal force. This force can be very great, and separations which proceed slowly by gravity can be speeded up enormously in centrifugal
 of milk may prevent germination germination, in a seed, process by which the plant embryo within the seed resumes growth after a period of dormancy and the seedling emerges. The length of dormancy varies; the seed of some plants (e.g.  and growth by these Clostridium spp.

Further information. Steven Ingham; phone: 608-265-4801; fax: 608-262-6872.
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Publication:Microbial Update International
Date:Dec 1, 1998
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