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Beer Starter Cultures as a Source of Microbial Contamination in Beer - An Investigation on Twelve Beer Starter Cultures from Four Different Manufacturers

Metto, Doreen LU (2016) KLGM01 20161
Food Technology and Nutrition (M.Sc.)
Abstract
The aim of this project was to assess the microbiological safety of twelve beer starter cultures produced by four different manufacturers by screening for microbial contamination. Enumeration of microorganisms was done on Tryptic Soy Agar (TSA), Rogosa agar, Reinforced Clostridial Agar (RCA), Baird- Parker agar, HiCrome agar and VRBD agar. The Enterobacteriaceae count was below the detection limit and isolates from both RCA and Rogosa agar were determined to be yeasts. Staphylococcus epidermidis was isolated from Safbrew S-04, Craft series M21 and Craft series M54 while Saccharomyces cerevisiae was the predominant microorganism growing on TSA agar.
Bacillus sp., Pantoea sp and Enterococcus sp. were isolated from HiCrome agar and a... (More)
The aim of this project was to assess the microbiological safety of twelve beer starter cultures produced by four different manufacturers by screening for microbial contamination. Enumeration of microorganisms was done on Tryptic Soy Agar (TSA), Rogosa agar, Reinforced Clostridial Agar (RCA), Baird- Parker agar, HiCrome agar and VRBD agar. The Enterobacteriaceae count was below the detection limit and isolates from both RCA and Rogosa agar were determined to be yeasts. Staphylococcus epidermidis was isolated from Safbrew S-04, Craft series M21 and Craft series M54 while Saccharomyces cerevisiae was the predominant microorganism growing on TSA agar.
Bacillus sp., Pantoea sp and Enterococcus sp. were isolated from HiCrome agar and a further analysis on HiCrome agar supplemented with Polymyxin B indicated the possible presence of Bacillus cereus in Safbrew S- 04, Safbrew S-033, Craft series M54 and White Labs British Ale Yeast WLP005. However, the colony counts were not sufficient to cause concern of a foodborne disease outbreak from the starter cultures.
A RT-PCR analysis was done for the enumeration of viable and non-viable Lactobacillus sp. in the beer starter culture by using primers targeting the 16S-23S rRNA intergenic spacer region. 11 out of the 12 starter cultures showed the presence of Lactobacillus sp. with the gene copy numbers ranging from 2.98 – 4.34 log copies/µl. A RT-PCR analysis for the presence of Bacillus sp. was desired but was not possible due to challenges faced with the chosen primers for this analysis. (Less)
Popular Abstract
Parties would not be the same without beer, it is the glue that holds all the fun together. It is therefore important for us to know about the safety of the beer we drink and more so, the safety of the yeasts that are used to ferment beer. The purpose of this project was to take a closer look at the yeasts used during the brewing of beer. Yeasts are the chief engineers in any brewing facility without which you would not be able to enjoy beer.
The yeasts used during the brewing of beer are very different depending on the type of beer you want. Yeasts used to brew lager beers are not the same as those used to brew ales. Therefore, to check for the safety of the yeasts twelve different commercial yeasts were looked at to check for... (More)
Parties would not be the same without beer, it is the glue that holds all the fun together. It is therefore important for us to know about the safety of the beer we drink and more so, the safety of the yeasts that are used to ferment beer. The purpose of this project was to take a closer look at the yeasts used during the brewing of beer. Yeasts are the chief engineers in any brewing facility without which you would not be able to enjoy beer.
The yeasts used during the brewing of beer are very different depending on the type of beer you want. Yeasts used to brew lager beers are not the same as those used to brew ales. Therefore, to check for the safety of the yeasts twelve different commercial yeasts were looked at to check for microorganisms that would normally cause foodborne diseases. It was found out that although some yeasts do contain some disease causing microorganisms, the levels they were in do not pose a threat to you, the beer lover. Despite this, and although beer itself is not very hospitable to bad microorganisms, it is of a slight concern that we found disease causing microorganisms in the yeasts used for the brewing of beer and more study is required to know if this is an issue that requires more attention. (Less)
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author
Metto, Doreen LU
supervisor
organization
course
KLGM01 20161
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Microbial pathogens, Beer, Microbial Contamination, PCR, food technology, livsmedelsteknologi
language
English
id
8882195
date added to LUP
2016-06-27 08:54:08
date last changed
2016-06-27 08:54:08
@misc{8882195,
  abstract     = {The aim of this project was to assess the microbiological safety of twelve beer starter cultures produced by four different manufacturers by screening for microbial contamination. Enumeration of microorganisms was done on Tryptic Soy Agar (TSA), Rogosa agar, Reinforced Clostridial Agar (RCA), Baird- Parker agar, HiCrome agar and VRBD agar. The Enterobacteriaceae count was below the detection limit and isolates from both RCA and Rogosa agar were determined to be yeasts. Staphylococcus epidermidis was isolated from Safbrew S-04, Craft series M21 and Craft series M54 while Saccharomyces cerevisiae was the predominant microorganism growing on TSA agar. 
Bacillus sp., Pantoea sp and Enterococcus sp. were isolated from HiCrome agar and a further analysis on HiCrome agar supplemented with Polymyxin B indicated the possible presence of Bacillus cereus in Safbrew S- 04, Safbrew S-033, Craft series M54 and White Labs British Ale Yeast WLP005. However, the colony counts were not sufficient to cause concern of a foodborne disease outbreak from the starter cultures. 
A RT-PCR analysis was done for the enumeration of viable and non-viable Lactobacillus sp. in the beer starter culture by using primers targeting the 16S-23S rRNA intergenic spacer region. 11 out of the 12 starter cultures showed the presence of Lactobacillus sp. with the gene copy numbers ranging from 2.98 – 4.34 log copies/µl. A RT-PCR analysis for the presence of Bacillus sp. was desired but was not possible due to challenges faced with the chosen primers for this analysis.},
  author       = {Metto, Doreen},
  keyword      = {Microbial pathogens,Beer,Microbial Contamination,PCR,food technology,livsmedelsteknologi},
  language     = {eng},
  note         = {Student Paper},
  title        = {Beer Starter Cultures as a Source of Microbial Contamination in Beer - An Investigation on Twelve Beer Starter Cultures from Four Different Manufacturers},
  year         = {2016},
}