PECTINATUS , A NEW GENUS OF BACTERIA CAPABLE OF GROWTH IN HOPPED BEER

128

130

Beer has been generally recognized as a microbiologically stable beverage. However, microbiological incidents occasionally occur in the brewing industry. The microbiological instability of beer is often caused by bacteria consisting of four genera, Lactobacillus, Pediococcus, Pectinatus and Megasphaera. Lactobacillus and Pediococcus belong to the lactic acid bacteria (LAB), whereas Pectinatus and Megasphaera form a group of strict anaerobes that are known as intermediates between Gram‐positive and Gram‐negative bacteria. The frequencies of beer spoilage incidents caused by these four genera have been reported to exceed 90% in Europe and therefore Lactobacillus, Pediococcus, Pectinatus and Megasphaera are considered to be the principal spoilage agents in the brewing industry. Thus, this review consists of three parts involving these four genera. The first part describes spoilage LAB in alcoholic beverages with some emphasis on beer spoilage LAB. In this part, the emergence and evolution of these spoilage LAB is discussed, the insight of which is useful for developing quality control methods for these beverages. The second part is devoted to the hop resistance in beer spoilage LAB. This area of research is evolving rapidly and recent progress in this field is summarized. The third part concerns Pectinatus and Megasphaera. Although this group of beer spoilage bacteria has been described relatively recently, the incident reports in Europe increased in the early 1990s, reaching around 30% of spoilage incidents. Various aspects of Pectinatus and Megasphaera, ranging from their taxonomy and beer spoilage ability to detection and eradication methods are described.

Section: Current Taxonomy Of Pectinatus and Megasphaeramentioning

confidence: 99%

Section: Current Taxonomy Of Pectinatus and Megasphaeramentioning

confidence: 99%

125th Anniversary Review: Microbiological Instability of Beer Caused by Spoilage Bacteria

Suzuki

2011

128

130

“…Pectinatus spp. produce considerable amounts of acetic and propionic acid as well as acetoin in wort and packaged beers 110,177 . Beer spoilage by Pectinatus spp.…”

Section: Fermentationmentioning

confidence: 99%

“…Beer spoilage by Pectinatus spp. is characterised by extensive turbidity and an offensive 'rotten egg' smell as a result of the production of hydrogen sulphide and methyl mercaptan 72,109,110 .…”

Section: Fermentationmentioning

confidence: 99%

Enhancing the Microbiological Stability of Malt and Beer - A Review

Vaughan

O'Sullivan

Sinderen

2005

167

While beer provides a very stable microbiological environment, a few niche microorganisms are capable of growth in malt, wort and beer. Growth of mycotoxin‐producing fungi during malting, production of off‐flavours and development of turbidity in the packaged product due to the growth and metabolic activity of wild yeasts, certain lactic acid bacteria (LAB) and anaerobic Gram negative bacteria, impact negatively on beer quality. It follows that any means by which microbial contamination can be reduced or controlled would be of great economic interest to the brewing industry and would serve the public interest. There has been an increasing effort to develop novel approaches to minimal processing, such as the exploitation of inhibitory components natural to raw materials, to enhance the microbiological stability of beer. LAB species, which occur as part of the natural barley microbiota, persist during malting and mashing, and can play a positive role in the beer‐manufacturing process by their contribution to wort bioacidification or the elimination of undesirable microorganisms. Other naturally occurring components of beer that have been valued for their preservative properties are hop compounds. It may be possible to enhance the antimicrobial activities of these compounds during brewing. Some yeast strains produce and excrete extracellular toxins called zymocins, which are lethal to sensitive yeast strains. Yeast strains resistant to zymocins have been constructed. Imparting zymocinogenic activity to brewing yeast would offer a defence against wild yeasts in the brewery. Thus, the antimicrobial properties of naturally occurring components of raw materials can be exploited to enhance the microbial stability of beer.

“…have been reported mainly from spoiled beer and pitching yeast 16 . They have also been isolated from drainage and water pipe systems of beer filling halls, parts of filling machines and the air and floor of filling halls, condensed water on ceilings, loose tiles and in cracks of damaged floors 3,7,32,35 . Plate counting and enrichment remain the principal methods for detection of microbial contamination in breweries during the brewing process and in final products 8 .…”

Section: Introductionmentioning

confidence: 99%

Occurrence of Pectinatus and Megasphaera in the Major UK Breweries

Paradh

Mitchell

Hill

2011

The occurrence of beer spoilage bacteria belonging to the genera Pectinatus and Megasphaera in ten major UK breweries was investigated. The sampling points were selected from fermentation areas, beer conditioning areas and beer bottling and canning sites. Multiplex PCR methodology was used for detection of three Pectinatus and three Megasphaera species using speciesspecific primers. The presence of six Lactobacillus species was also examined. Overall, 117 samples were analysed from ten breweries; six samples were positive for the presence of Pectinatus species and three samples were positive for the presence of Megasphaera species, while 34 samples were positive for the presence of Lactobacillus species. Lactobacillus species appeared to be the major potential spoilage microorganisms. Although none of the actual beer samples were found to be positive for Pectinatus and Megasphaera species, their occurrence in aerobic brewery environments indicates sanitation problems and revealed the presence of highly established biofilms in some breweries.