The laboratory storage of brewing yeast stocks cultures over a number of years. It has been demonstrated that the genetic stability and survival of brewing yeast strains are optimal after cryopreservation at ultra-low temperatures (below -139 °C) compared to other preservation methods. The cultures may be stored in plastic tubes or straws. The present method describes the preservation in polypropylene straws under liquid nitrogen or in mechanical freezers. Descriptors: yeast storage at ultra-low temperatures, cryoprotectant agent, long-term storage, cryopreservation,  dehydration, osmotic imbalance, intracellular ice.

This method describes the storage of brewing yeast strains for short periods of time (up to 6 months) in the laboratory. Changes in brewing yeast genotype following maintenance of the strains by repeated subculturing have been reported to influence yeast brewing performance. Preservation of the original properties of the stored yeasts in the long term is only recommended at ultra-low temperatures. For short-term storage (up to 6 months), other methods are available that allow safe and simple management of strains in the lab. Repeated subculturing for preservation of brewing yeast should be totally avoided. Descriptors: yeast subculturing for short-term storage.

It is necessary to use EBC Microbology 3.4.1

The shipment of brewing yeast strains from a supplier laboratory to a receiving laboratory  where they are to be propagated for industrial purposes. Descriptors: yeast strain transport, short-term storage, free from contaminant microorganisms.

It is necessary to use EBC Microbiology 3.4.2

Propagation of brewing yeast strains from stock cultures to obtain sufficient yeast to pitch the first propagation tank in the brewery. As the objective is to produce large numbers of yeast cells (not to produce beer), the propagation conditions are more flexible than in brewery fermentation, so general guidelines, as well as a standard protocol as a guide are provided. Descriptors: laboratory storage.

it is necessary to use EBC Microbiology 3.4.1 and 3.1

The determination of the percentage of cells in a yeast culture which are respiratory deficient (known as “petite mutants”, or simply “petites”). Descriptors: detection and enumeration of respiratory deficient mutants, deficiency in metabolism, low yield of biomass, diacetyl formation.

This technique allows the prediction and evaluation of the stability of brewing characteristics in a strain of yeast, and also permits the study of the influence of certain technological parameters on its behaviour in fermenter. It can also be used to assess the characteristics of newly isolated yeast cultures. Descriptors: yeast characterisation by fermentation in EBC Tall Tubes.

Classification of yeast isolates according to their ability to flocculate or form flocs. Descriptors: Gilliland Method,  yeast analyis,  aggregation of yeast cells.

Differentiation of Gram positive and Gram negative bacteria. Descriptors: Gram Staining for Differentiation of Bacteria,  cell wall structure, crystal violet dye, red saffranin.

Rapid differentiation of Gram positive and Gram negative bacteria. Descriptors: KOH Method for Gram Differentiation.

Differentiation of catalase positive and catalase negative bacteria. Descriptors: Catalase Test, enzyme catalase, decompose hydrogen peroxide (H2O2) into H2O and O2.

Differentiation of oxidase positive and oxidase negative bacteria. Descriptors: Oxidase Test, tetramethyl-p-phenylene diamine, enzyme oxidase.

Yeasts isolated on agar plates can be checked for spoilage potential by their ability to decarboxylate an organic acid, producing a distinctive odour. This method, originally described by EBC, was adopted by the ASBC as an international method in 2016 / 2017 and reciprocated as an international method by EBC under the same number in 2018. Descriptors: Phenolic Off Flavour (POF), decarboxylate ferulic acid to 4-vinyl guaiacol, aroma of cloves.

Descriptors: Identification of colonies (bacteria or yeasts) from agar plates or membrane filters by their capability to catabolise different nutrients.

It is necessary to use EBC Microbiology 2.3.3.3

Analysis of turbid samples (enrichments or yeast containing) and of colonies from agar plates for the presence and identification of bacteria, yeasts and/or moulds by detection of their DNA (deoxyribonucleic acid). Descriptors: Detection and Identification of Microorganisms from Turbid Liquid.

It is necessary to use EBC Microbiology 2.3.9.1 to 2.3.9.5

Analysis of filterable samples for the presence and identification of bacteria, yeasts and/or moulds by detection of their DNA (deoxyribonucleic acid). Descriptors: Detection and Identification of Microorganisms from Filterable Samples by Real-Time PCR (Polymerase Chain Reaction), PCR analysis, DNA Extraction, PCR thermocycling instrument, specific primers and probes systems in PCR, lysis buffer, DNA polymerase (usually TaqPolymerase), RealTime PCR thermocycling instrument,  Real Time PCR, ready-to-use DNA extraction kits and PCR applications.

It is necessary to use EBC Microbiology 2.3.2.1 and 2.3.9.1 to 2.3.9.5

Descriptors: Identification of colonies (bacteria, yeasts and/or moulds) from agar plates or membrane filters by specific detection of their DNA (deoxyribonucleic acid).

In trouble shooting and tracing of contamination routes, identification below the species level is often useful. Ribotyping is a DNA fingerprinting technique enabling the discrimination of bacterial strains within the same species from each other. Species identification can be achieved at the same time, if a relevant ribopattern identification database is available. Descriptors: Bacteria Ribotyping, restriction fragment length polymorphism analysis, restriction enzymes, fingerprints (ribopatterns).

It is necessary to use EBC Microbiology 2.3.3.3

Determination of the yeast cell concentration in stored pitching yeast, fermenting or stored beer. Descriptors: Haemocytometry, counting chamber, counting chambers (Thoma, Malassez, Bürker-Türk, Neubauer), counting area.

Instrumental determination of the yeast cell concentration in fermenting beer or pitching yeast. Descriptors: Electronic Counter, modifies the resistance between the electrodes, electrolyte.

Determination of the yeast cell concentration of stored pitching yeast, fermenting or stored beer with counts over 1 million cells per ml. A concentration step is necessary for samples containing less than 1 million cells. Descriptors: Photometric Determination,  photometer,  calibration curves.

It is necessary to use EBC Microbiology 3.1.1.1 or 3.1.2.2