Using SIFT-MS for detection of beer spoilage bacteria and compounds causing off-flavour in beer

Abstract

Selected ion flow tube mass spectrometry (SIFT-MS) was used for detection of spoilage bacteria in wort and beer. Samples were analysed in triplicate using SIFT-MS Full Scan mode to identify volatile compounds in the headspace of the samples. Volatile compounds in wort headspace included acetaldehyde, propanol, 2-methylpropanal, hexanal, methanethiol, 2-methylbutanal. Volatile compounds in the headspace of the wort inoculated with Lactobacillus brevis included ethanol, acetic acid and propanol. The following compounds were identified in the headspace of the sample of degassed beer: ethanol, propanol, 2-methyl-1-propanol, acetaldehydes, and ethyl formate. The detected volatile compounds coming from the headspace of wort inoculated with Lactobacillus brevis revealed changes in the compounds due to unwanted bacterial fermentation. In addition, an unidentified product ion having m/z 39 was detected. Calculations of relative abundance for this product ion and further investigations demonstrated that it can be considered as a result of compounds formed due to contamination with L. brevis. These data suggest that SIFT-MS has great potential for detection of volatile compounds coming from beer spoilage bacteria.