HEAT RESISTANCE OF BACTERIA IN ALCOHOL-FREE BEER
Date
1995
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
Two of the most heat resistant beer spoilage organisms found to date, Pediococcus acidilactici and Lactobacillus delbrueckii, and two human pathogens, Escherichia coli 0157:H7 and Salmonella typhimurium (both recently associated with outbreaks of diarrhea and hemolyticuremic syndromein apple cider), were tested for heat resistance in commercial alcohol-free beer and commercial 5% alcohol beer. Using the attemperated dilution blank adaption of the multiple point method, known cell concentrations were inoculated into 5%
alcohol beer and alcohol-free beer held at a variety of heating temperatures.
Survival curves, D values, phantomthermal death time curves, and Z values were determined. Decimal reduction times at 600C (D6o), a common temperature for beer pasteurization, were obtained by extrapolation. Pathogens demonstrated 3 to 17 times more heat resistance in alcohol-free beer and both lactic acid bacteria showed an increased resistance to heat of 4 to 7 fold in alcohol-free beer compared to 5% alcohol beer. Results illustrated a significant difference in the pasteurization parameters required to achieve microbiological stability of alcohol-free beers compared to 5% alcohol beer. Although pathogens tested are not at all heat resistant, and do not survive pasteurization temperatures even over short time intervals, these organisms can grow in alcohol-free beer and industry is cautioned about the safety and sale of unpasteurized low alcohol products when processed by filtration.
Description
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Citation
Degree
Master of Science (M.Sc.)
Department
Food and Bioproduct Sciences
Program
Applied Microbiology and Food Science