Development of Bacterial Contamination during Production of Yeast Extracts
Claude Champagne , Barrette, J., J. Goulet
Nom de la revue: Applied and Environmental Microbiology 65(7): 3261-3263.
[Effects of autolysis promoters and pH on contaminating bacterial populations in yeast extract production were investigated.] Bakers' yeast suspensions having bacterial populations of 10^6 and 10^8 cfu/ml were subjected to autolysis processes designed to obtain yeast extracts (YE). The bacterial contaminants added to the yeast cell suspensions were produced with spent broths obtained from a commercial yeast production plant and contained 59% cocci (Leuconostoc, Aerococcus, Lactococcus) and 41% bacilli (Bacillus). Autolyses were conducted at 4 different pH levels (4.0, 5.5, 7.0 and 8.5) and with 2 autolysis-promoting agents (ethyl acetate and chitosan). Processing parameters were more important than initial bacterial population in development of contaminating bacteria during manufacture of YE. Drops in viable bacterial population after a 24-h autolysis were observed when pH was adjusted to 4.0 or when ethyl acetate was added. A signfiicant interaction was found between the effects of pH and autolysis promoters on bacterial population in YE, indicating that activity of ethyl acetate, as opposed to that of chitosan, was not influenced by pH.