title: Inability of dairy propionibacteria to grow in milk from low inocula.
abstract: Growth of propionibacteria in complex media was independent of the initial number of cells; in contrast, growth of propionibacteria in milk and whey did not occur if the initial level of cells was < 10(6) cfu/ml. Addition of vitamins, minerals or complex nitrogen sources to the milk or whey, or incubation under anaerobic conditions had no effect on the lack of growth. Addition of freeze-dried whey, prepared from skim milk reconstituted from powder, to a complex medium prevented growth from low inocula in the complex medium, demonstrating the presence of an inhibitor or inhibitors in the whey. The inhibitor(s) was heat stable, had a low molecular mass and retained its activity for at least 4 weeks at 20 degrees C. Pregrowth of some lactic acid bacteria, used as starter cultures in Swiss-type cheese manufacture, in milk for 2 weeks at 20 degrees C removed the inhibition, which explains how propionibacteria develop in Swiss-type cheese from low numbers even though they are inhibited in milk.
authors.affiliation: Department of Microbiology, University College, Cork, Irish Republic.
authors.forename: P
authors.initials: P
authors.lastname: Piveteau
authors.forename: S
authors.initials: S
authors.lastname: Condon
authors.forename: T M
authors.initials: TM
authors.lastname: Cogan
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D004355:Drug Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007778:Lactobacillus / Q000254:growth & development; D008892:Milk / Q000382:microbiology*; D008894:Milk Proteins / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology; D008970:Molecular Weight; D011424:Propionibacterium / Q000187:drug effects / Q000254:growth & development*; D013696:Temperature; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D000067816:Whey Proteins