Production of Volatile Materials in Milk by Some Species of Bacteria

Open Access
Publisher Website
Google Scholar
Abstract
Volatile materials produced at different periods of growth in milk were measured in attempts to characterize various organisms. Comparisons were made of 3 different strains of Aerobacter aerogenes, 2 strains of Escherichia coli and 2 strains of Streptococcus faecalis var. liquefaciens. One strain each of Achromobacter lipolyticum and Streptococcus diacetilactis were compared in 2 trials. In addition one strain each of Escherichia freundii, Streptococcus lactis, Lactobacillua acidophilus, Lactobacillus casei and Pseudomonas fragi were tested in single trials. Patterns of volatile materials obtained by gas liquid chromatographic (GLC) analyses were plotted for each organism strain. Duplicate trials were made by culturing each strain in 2 separate flasks. All cultures were grown in milk which was first autoclaved then subsequently distilled aseptlcally at 60-65 C under 20-25 cm Hg. (to remove indigenous volatile materials). Cultures were incubated at 25C and GLC analyses were made by head space gas sampling. Bacterial counts were recorded at the beginning and end of each test period. Except for A. aerogenes, which could not be distinguished from E. coli or E. freudnii, and S. diacetilactis which produced volatiles very similar to Ach. lipolyticum, other organisms could be differentiated by their patterns. In some cases the time for appearance or rate of development of a certain volatile was unique. Initial and final bacterial counts gave an indication of the numbers of organisms involved.