Rusty Spot in Cheddar and other Cheese: II. Factors Controlling the Pigmentation of the Causative Organism

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Abstract
It has been observed that media containing tissue extracts promote pigmentation of the organism causing “rusty spot” in cheese. Growth, but not pigment, may be obtained in a medium containing a fermentable carbohydrate and a suitable protein digest.The substance in tissues promoting pigmentation has properties similar to those of vitamin B.In addition to these chemical requirements, moisture and surface in a medium greatly stimulate pigmentation.Pigment is only produced when the medium is at an oxidation-reduction potential below that at which litmus is reduced.The following factors appear to govern the growth and pigmentation of this organism: (1) a certain range of oxidation reduction potential; (2) moisture; (3) surface; (4) a fermentable carbohydrate; (5) a minimum concentration of soluble available N; (6) a factor closely associated with, but not identical with, vitamin B1.Certain properties of the factor are described.The relation of this investigation to “rusty spot” in cheese is discussed.