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Ripening Cheese…How Does Cheese Maintain Its Balance?-Kosikowski Style

 

 


“At its peak, usually within 24 hours of transformation from fluid to a solid, the cheese contains many billions of bacteria.  In time, most of these bacteria succumb to the bleak, harshness of the anaerobic environment inside the cheese, but not without leaving behind a biological legacy of active cellular enzymes which produce low molecular weight compounds such as fatty acids, ketones, amino acids, amines and carbon dioxide.

Where do the bacteria of the cheese come from….They come from small numbers from the healthy udder, from post-contamination of the milk or cheese anywhere along the processing route, or through purposely culturing the cheese milk with pure cultures

…Other bacteria exist in small numbers, initially, in the young cheese and then grow unexpectedly, triggered by curious symbiotic relationships.

…Tracking bacteria in a ripening cheese is a complex operation.  There may be certain species or strains in cheese which remain unknown simply because of a lack of proper culture media or technic.

…Coliforms, including E. coli , grow well in warm or cold cheesemilk, and in cheese curd.  Their numbers may reach 100 to 500 million per gram if the levels in cheesemilk were substantial and curd acid development was slow…These spoilage bacteria attain a peak when the cheese is put to press and, thereafter, die relatively rapidly at optimum pH 5.0-5.2…Coliforms do not survive in pasteurized cheese milk, but may be present in the resulting cheese due to post contamination…

…it is yeast like Candida (Saccharomyces), Pichia, Torulopsis, or Hansenula which first emerge on their surfaces.  They grow and utilize the readily available lactic acid which raises the initial pH 4.6 of the cheese surfaces, creating better conditions for growth of the mold and aerobic bacteria to follow and the activity of their strong proteolytic and lipolytic cell enzymes.  Such yeasts are essential to establishing a proper environment…

The Molds of Cheese (P. = Penicillium)

P. Camembertii (White)

P. Candidum (White)

P. Nalgiovensis (Pinkish-White)

P. Roqueforti (Blue-green)

P. Glaucum (Blue-green)

Mucor rasmusen (Black green)

Actinomucor elegans (White, from bean curd)

Enzymes

The enzymes prevailing in ripened cheese, omitting rennin and other added enzyme preparations if any, originate from the milk as natural tissue enzymes, seeping inadvertently with blood across the membrane barrier into the udder, or become freed from the millions of bacteria, yeast, or mold cells autolyzing in the cheese.

Most familiar natural milk enzymes: protease, lipase, alkaline and acid phosphatase, catalase, and peroxidase.

…Natural milk enzymes, peroxidase excluded, are heat labile, unable to withstand minimum pasteurization temperatures, and are not highly active at the pH range of young ripening cheeses, usually pH 4.6-5.5.  In Camembert, Brie, or Blue, the pH rises with age to become mildly alkaline so in such advance cheese ripening natural milk enzymes may play an important role…it is difficult to confirm their contributions.

The microbial cell enzymes differ in this respect…Endocellular enzymes appear in large concentration after the cells die and autolyze. Also, some extracellular microbial enzymes probably contribute to important reactions involved in a ripening cheese, particularly those from mold or yeast….Most of these microbial enzymes are heat stable, and display high activity at the normal intial pH of a cheese…lipases, proteases, amino acid decarboxylases, and deaminases.

Besides controlling the lactic acid fermentation, salt partially solubilizes monocalcium paracasein.  Thus…salt helps give a smoothness and plasticity of body not fully attainable in its absence.

The ripening …of a cheese means placing a green or young cheese form in a temperature and relative humidity controlled area for a specific period.  During this incarceration, the cheese curd breaks down into a smooth body and a characteristic flavor…Cheddar cheese ripens best at 5 degrees C and 85 percent relative humidity…Blue cheese requires 10 degrees C and 95% humidity for intial development of its mold mycelia and 4 degree C and 90 percent relative humidty for typical flavor

…Presently, the popular temperatures of commercial ripening range from 1 to 10 degrees C [for Cheddar]…The point is reemphasized that for any given cheese variety, the ripening conditions are characteristic for that cheese, dictated by composition, microbial load, and surface charcteristics; otherwise it would not attain consistent properties.

…Ripening creates many other changes…Freshly pressed Blue cheese displays a pH of 4.8, but in 4 months, at 7 degrees C, it rises, perhaps to pH 7.2…

Amino acids, fatty acids, methyl ketones of different carbon length, lactones, and many other organic compounds become free in the cheese and concentrate, dpeendent upon particular cheese types and the ripening conditons.  Tyrosine…is highly insoluble and, in older cheeses, forms crystals.

…In mold ripened cheese, normally carbon dioxide is given off heavily…but then later when the pH increases, ammonia is also generated.

…Natural cheese, as a biological entity, is a dynamic microlaboratory of complex reactions guaranteed to capture and hold the interest of the most imaginative biochemist, microbiologist and technologist.”

Frank Kosikowski, Cheese and Fermented Milk Foods

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