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

Abstract

SummaryIt 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.