Slimy and ropy milk

Abstract

<p>A study of slimy and ropy milk sent for examination to the dairy bacteriological laboratories of Iowa State College has shown the following:</p> <p>1. Cultures of organisms secured from slimy starters, apparently typical Streptococcus lacticus forms, sometimes showed marked capacity to produce ropiness when inoculated into sterile milk. This slime producing power is evidently a variable characteristic, appearing and disappearing without apparent cause.</p> <p>2. Associative action of organisms in some cases is responsible for ropiness. Two organisms, neither of which alone can cause ropiness, may, when grown together, cause the medium to become slimy.</p> <p>3. Bacterium (lactis) viscosum is one common cause of slimy milk.</p> <p>4. Certain peptonizing bacteria, as Bact. peptogenes, produce a very slimy residuum after digestion of the casein.</p> <p>5. Bacterium bulgaricum and certain related high acid organisms frequently produce marked viscosity in milk.</p> <p>Sliminess in milk is apparently due to different causes with different organisms:</p> <p>1. Gum and gum-like capsular materials partially soluble, or at least swelling in water, al'e frequently the same.</p> <p>2. In many cases there seems to be a direct relationship between chain formation of streptococcus and the development of ropiness, likewise between the numbers of bacteria and ropiness.</p> <p>3. Associative action between two distinct organisms resulting in great increases in number of each is not uncommon as a cause of ropiness.</p> <p>Methods of control and prevention of slimy milk are discussed.</p> <p>Keys to the organisms that have been described as responsible for slimy production in milk are presented. An attempt has been made to clear up synonymy. Descriptions of thirty-three species of bacteria that have been found associated with milk are given, and the literature reviewed.</p>