SPECIFIC SPOILAGE ORGANISMS IN BREWERIES AND LABORATORY MEDIA FOR THEIR DETECTION

The Cram positive bacteria are generally regarded as the most hazardou s beer spoilage organisms in modern breweries, especially the lactobac illi: L. brevis, L. lindneri i, L. curvatus, L. casei, L. buchneri, L. coryneformis, L. plantarum, L. brevisimilis, L. malefermentans, and L . parabuchneri and the pediococci: P. damnosus, P. inopinatus and P. d extrinicus. Micrococcus kristinae is the only species within the micro cocci relevant to brewing. The Gram negative strictly anaerobic bacter ia are apparently increasing in importance and include Pectinatus cere visiiphilus, Pectinatus frisingensis and Selenomonas lacticifex, repor ted as obligate beer spoilage organisms; Zymophilus raffinosivorans a potential beer spoilage organism; Megasphaera cerevisiae as an obligat e spoilage organism of low alcohol beer and Zymomonas mobilis as capab le of spoiling primed beer. With improved process technology the impor tance of aerobic bacteria has decreased and the same applies for the G ram negative aerobic bacteria Hafnia protea and Enterobacter cloacae w hich are capable of surviving beer fermentation. Beer spoilage organis ms include several so-called wild yeasts, of which Saccharomyces speci es are generally considered the most important. Even though the detect ion of beer spoilage organisms by cultivation in laboratory media does not always provide the specificity and the sensitivity required, the use of selective media and incubation conditions still appears to be t he method preferred by breweries. The media used depend on the type of sample, the specificity required and, for detection of wild yeasts, t o some extent, the characteristics of the culture yeast. Among the med ia reported so far no single medium can be used to detect all members within a group of specific beer spoilage organisms and further work on the development of improved substrates are required both for bacteria and wild yeasts.