Mold-ripened Cheeses Research Articles

Inactivation of Penicillin by Cheese

Penicillinase-like activity among commercial blue mold-ripened cheese was discovered in research originally initiated to investigate the possibility of penicillin arising in such cheese from the normal penicillin mold required for its manufacture. No penicillin production was observed. Over 60% of 70 Blue and Roquefort cheese analyzed destroyed, in some instances completely, added penicillin upon contact, indicating that ingestion of these cheeses may be beneficial to penicillin-sensitive persons. Swiss, Camembert, and Cheddar cheese did not exhibit this penicillinase-like activity.

Fatty acid oxidation by spores of Penicillium roqueforti.

When 1 mum sodium octanoate was the substrate for spores, most of the molecule was recovered as CO(2) and no ketone was produced. However, when larger concentrations (20 mum) were used as substrate, part of the molecule was converted to methyl ketone and part was completely oxidized. Optimal conditions for the production of 2-heptanone were determined because of the importance of this compound in giving aroma and flavor to mold-ripened cheeses. Optimal ketone formation was not dependent upon the temperature and length of time at which the spores were stored. The spore suspensions were stored for over 36 months at 4 C without losing their ability to convert octanoic acid to 2-heptanone. The oxidation of octanoic acid was inhibited by cyanide, carbon monoxide, mercury, 2,3-dimercapto-1-propanol, and alpha, alpha-dipyridyl. No ketone was produced under anaerobic conditions. Although no intermediates of fatty acid oxidation were isolated, since an active cell-free preparation could not be obtained, this investigation has yielded some evidence for the beta oxidation of the fatty acids by spores of Penicillium roqueforti.

Fatty Acid Oxidation by Spores of Penicillium roqueforti

When 1 mum sodium octanoate was the substrate for spores, most of the molecule was recovered as CO(2) and no ketone was produced. However, when larger concentrations (20 mum) were used as substrate, part of the molecule was converted to methyl ketone and part was completely oxidized. Optimal conditions for the production of 2-heptanone were determined because of the importance of this compound in giving aroma and flavor to mold-ripened cheeses. Optimal ketone formation was not dependent upon the temperature and length of time at which the spores were stored. The spore suspensions were stored for over 36 months at 4 C without losing their ability to convert octanoic acid to 2-heptanone. The oxidation of octanoic acid was inhibited by cyanide, carbon monoxide, mercury, 2,3-dimercapto-1-propanol, and alpha, alpha-dipyridyl. No ketone was produced under anaerobic conditions. Although no intermediates of fatty acid oxidation were isolated, since an active cell-free preparation could not be obtained, this investigation has yielded some evidence for the beta oxidation of the fatty acids by spores of Penicillium roqueforti.

Assay of Various Mold-Ripened Cheeses for Antibiotic Activity

Summary A study was made to determine whether antibiotics are present in mold-ripened cheeses. The assay method used relied upon the titratable acidities, calculated as lactic acid, produced by regular commercial dairy cultures. The suitability and accuracy of the method was tested by additions of known quantities of penicillin to preparations containing mold-ripened cheese. The method was sensitive to a concentration of 2.0 units of penicillin per gram of cheese. Fourteen different commercial brands of mold-ripened cheeses were assayed.The samples of cheese included five Blue, three Roquefort, three Camembert, and three Nuworld. One brand of Blue and three brands of Roquefort were imported (Denmark and France, respectively), and the remainder were manufactured in the United States. None of the samples of cheese tested contained as much as 2.0 units of penicillin per gram of cheese. No other culture inhibitory substances were present in the cheese in such concentration that they could be detected when as much as 10% cheese was included in the culture preparations assayed. For all practical purposes it may be concluded t h a t there is no penicillin present in commercial Blue, Roquefort, Camembert, or Nuworld cheese.

The Methyl Ketones of Blue Cheese and their Relation to its Flavor

Summary By means of a steam distillation and ether extraction procedure, it has been possible to recover material from blue cheese containing a high concentration of methyl ketones. By fractional distillation of this material relatively pure fractions of pentanone-2, heptanone-2 and nonanohe-2 were obtained. Acetone was identified as a constituent of the ether-extracted steam distillate from blue cheese. These methyl ketones would appear to be formed from the fatty acids in the cheese by beta-oxidation. Similarity in odor between these ketones, particularly heptanone-2 and that of blue cheese was noted by a number of observers during the course of this investigation. It seems probable that minute quantities of these methyl ketones are the constituents which make the flavor of mold-ripened cheeses distinctly different from the flavor of other types of cheese.