If a water sample is run through a strongly acidic cation exchanger, all of the cations are replaced with hydrogen ions, thus producing the corresponding free acids in equivalent quantities (total mineral acid value). Since the carbonates and bicarbonates are transformed into carbon dioxide and therefore escape determination, their content must be determined through titration with acid to a pH of 4.3 (m value).
This method describes how to calculate the concentration of sodium and potassium ions in water.
Since analyses for determining the concentrations of sodium and potassium ions in water require considerable effort, and these ions are not very relevant for evaluating the suitability of water for the processes of brewing and malting, a simple calculation will suffice. The difference in the concentrations of anions and cations in the water is determined, allowing the calculation to be performed under the assumption that only sodium ions are present in the water.
The method lists the equipment that is important in a brewery microbiology laboratory.
Microbiology laboratories in the brewing and beverage industry and its suppliers
Gas burner
A Bunsen burner or a Teclu burner is used for annealing and flaming. If no gas connection is available, a cartridge burner can be used, which is placed on a propane or butane gas cylinder (Fig. 1).
Fig. 1: Valve cartridge burner
Burners with toggle levers that can be operated with the heel of the hand are ideal for conveniently switching between flame and pilot flame (Fig. 2).
Fig. 2: Bunsen burner with toggle lever
From the perspective of improved occupational safety, electric burners that do not require a pilot flame or that do not emit gas when flameless, even when the gas tap is open, also work well (Fig. 3).
Fig. 3: Electrical safety Bunsen burner
Water bath
Water baths can be used in microbiology labs for various purposes, such as dissolving and liquefying agar culture media, tempering agar culture media, tempering or cooling cultures, etc.
Water baths that have an agitator or pump to constantly circulate the water, offer high temperature accuracy and consistency. Water baths can help to reach the desired temperatures more quickly than an incubator. The bath can usually be set to temperatures of 5-100 °C.
Useful features include a temperature selector limiter, a level controller to compensate for evaporation loss and tap water cooling, as well as a sloping or domed lid that minimises heat and evaporation loss and drains condensation water so that it does not drip onto the culture vessels.
Water baths may only be filled with distilled and demineralised water to prevent calcification. A non-liquid preservative can be added to the water to prevent bacterial growth in the bath.
Balances
Balances are mainly used in microbiological laboratories for weighing culture medium components. In most cases, balances with a readability of 0.01 g should be sufficient. In isolated cases, certain substances (e.g. minerals, antibiotics) may need to be added in even smaller quantities, which may require precision scales with a readability of 0.001 g.
pH meter
Checking the pH value of culture media plays an important role in microbiology, as the growth behaviour of microorganisms is decisively influenced by the pH value. It should be noted that the pH value must be measured before and after autoclaving, as this can change the pH value.
In addition to the standard pH electrodes for measuring in liquids, puncture electrodes may also be recommended for determining the pH value of solid culture media.