Microbial biofilms can form in dispense outlets as a result of poor or inadequate cleaning and can be difficult to remove using conventional practices. Enzymatic cleaners might help to remove biofilms by degrading the exopolysaccharide layers in which the microbes are embedded. A multispecies biofilm comprising wild type dispense isolates of Flavimonas oryzihabitans, Lactobacillus brevis, Leuconostoc mesenteroides and Saccharomyces cerevisiae was generated on a section of tubing and fitted into a pilot dispense system, which was left uncleaned for 12 weeks. After cleaning approximately 104 viable aerobes and 103 viable anaerobes were still present. Stainless steel coupons and pieces of dispense line contaminated with biofilm were incubated in the laboratory with an enzyme mix containing varying proportions of α‐amylase, β‐glucuronidase, glucose oxidase, dextranase, protease and pectinase. Cultures grown on stainless steel had significantly (F pr. > 0.05) less viable cells than non‐enzyme treated biofilms, but this was dependent on the microbial species. Typically Lactobacillus brevis was most susceptible to the enzyme treatment. Cultures grown on dispense line were much more resistant to enzymatic digestion. Pre‐digestion with protease was most effective for removal of Lactobacillus brevis and Leuconostoc mesenteroides but not for Saccharomyces cerevisiae and Flavimonas oryzihabitans. In the simulated bar, pre‐digestion with protease reduced the viable cell count by 0.64 log units for the aerobes and 1.9 log units for the anaerobes. This study demonstrates that pre‐digestion with enzyme solutions before line cleaning is useful for treating heavily contaminated lines in trade.
Aims: To design and evaluate PCR primers for the rapid detection of Obesumbacterium proteus. Methods and Results: The 16S rDNA from a wild-type Obesumbacterium proteus biotype II isolate was sequenced and the resultant data used to produce specific primers for this organism. These primers discriminated between biotype I (nonbrewery) and biotype II isolates. In addition, the primers were able to detect Obesumbacterium proteus in wort and in yeast slurries in the presence of competitive bacteria. The primers were tested against a range of other beer spoilage bacteria for any cross-reactions. None were detected. Conclusions: Obesumbacterium proteus primers can detect this contaminant without generating cross-reactions to related species. Significance and Impact of the Study: The primers generated in this study can now be used for PCR detection assays that will contribute to early detection of this important process contaminant.
Fish products have been identified as serious allergens and people who are allergic to fish must avoid consuming foods made with fish or fish products. There is no evidence that isinglass (which is made from the swim bladders of certain fish) can cause allergenic reactions in people who are allergic to fish, and the European Food Safety Authority (EFSA) has ruled that it is not very likely to do so. However, many people may still wish to avoid drinking beer which has been clarified with isinglass. Two alternative compounds (which had shown promise in earlier experimental trials) for the clarification of cask ales and brewery conditioned beers were investigated. These were avian collagen and a pea protein extract. Both materials were observed to have a good clarification effect in laboratory scale fining trials and performed well in comparison to isinglass. Brewery trials were conducted using isinglass, avian collagen and pea extract as fining agents and sensory evaluation showed that there were few discernable differences between all three beers. The collagen alternative was ideal in that the data obtained from the laboratory, sensory and analytical trials show that it acted in a similar manner to isinglass and has no significant impact on beer quality. However, it was not thought that brewers would be receptive to using animal products in their beer. The pea extract also worked well and would make an excellent vegetarian alternative to isinglass, however further work is needed to scale up the production of the pea extract in order that it should become an economic option for use in the beer and wine industries.
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