Patent GB-1175472-A (GB)
Title: Cheese Production
Inventor: TOOLENS HUIBRECHT PIETER
IPC: A23C19/032
Filed: 1968-03-01
Abstract: 1,175,472. Colourless mutants of Brevibacterium linens and Arthrobacter sp. UNILEVER Ltd. March 1, 1968 [March 1, 1967], No. 9999/68. Heading C6F. [Also in Division A2] The red-brown to orange discolourations of Brevibacterium linens or Arthrobacter sp. on the white mycellium of Penicillium caseicolum or Penicillium camemberti in the production of Camembert or Brie cheeses, are avoided by selecting and using colourless mutants of the Brevibacterium linens or Arthrobacter. The colourless mutants may be obtained by selective cultivation, but preferably cultures of these micro-organisms are first treated with sunlight, ultraviolet light, gamma rays, X-rays or neutrons, or such chemical mutating agents as yperite, nitrous acid, fermamide and imino-acetylene. Cultures in logarithmic growth in a medium free from albumin are exposed for 2 to 6 minutes to ultraviolet irradiation (wavelength 260 mÁ) of an intensity of about 1000 ergs per sq. mm. per minute. Alternatively, the cultures may be subjected for 0.5 to 8 minutes to R÷ntgen radiation (wavelength 0.182 A or 0.210 Š) with an intensity of about 1.4 to 2 Mrad/h. After the mutating treatment has taken place the culture is kept in darkness for a time before the colourless mutants are isolated by selective cultivation. According to an example, cells of Brevibacterium linens are subjected to irradiation at a distance of 10 cms. by means of a 6-watt low-pressure gas discharge lamp emitting ultraviolet light of a wavelength of 254 mÁ. The intensity of irradiation is about 1000 ergs per sq. mm. per minute - irradiation lasts for 2 minutes and results in the death of about 99% of the cells. During the course of the irradiation the cells are subjected to magnetic stirring. Thereafter, the suspension is kept in darkness for 3 hours at 20‹ C., after which a culture is produced of all the surviving cells. Colonies of colourless cells are sown on various media with an NaC1 content of 5 to 7% and selection of the cells is made on the basis of salt resistance. For the preparation of Camembert, 3% of a culture of lacto-bacilli containing 10<SP>10</SP> to 10<SP>11</SP> cells per ml, 10 ml. of a suspension of Penicillium caseicolum spores (20 to 30 x 10<SP>6</SP> spores per ml. ) and 2g rennet powder are added to each 100l of milk and the milk treated in this way is kept at 32‹ C. for 2 hours. Immediately after the cheeses are formed, they are immersed in a 20% NaC1 bath so that they may absorb about 2.5% salt. Just before salting the cheese, 2.5 ml. of a culture of the mutated Brevibacterium linens is added to 100l of the brine so that there are 10,000 germs per ml. of brine. The microorganisms begin to grow as soon as the pH of the cheese is about 6.0 at least. The cheese is matured in chambers where a temperature of 16‹C. and a relative humidity of 90% are maintained. Mould develops on the cheese in the form of a white layer progressing from the surface to the centre. After the cheeses have been kept there for 10 days they are packed in perforated aluminium foil. The Brevibacterium linens destroys the sapid substances giving rise to an unpleasant, bitter taste so that the cheese becomes mild and continues to mature. The procedure of a further example involves exposing cells of Brevibacterium linens to irradiation emitted from a tungsten spectrographic tube at a distance of 2 cm. The intensity of irradiation was 1.4 Mrad/h.