Search: indicator organisms

Biological process control in breweries involves testing water, wort, yeast, beer, air, and gases that are in contact with wort and beer as well as other substances, e.g. clarifying agents, for microbial contamination. In addition, the pipework of beer, water and pressurised gas as well as equipment, machines and containers that come into contact with water, wort, yeast or beer are tested.

In all these tests, the aim is to detect obligate beer-spoilage organisms in particular, but in special cases also those that can lead to beverage contamination as potential beer-spoilage organisms.

"Indirect beer-spoilage organisms" are microorganisms that can damage intermediate products such as yeast and wort, whereby this preliminary damage can be carried over into the bottled beer (e.g. Enterobacteriaceae in the wort pathway or in propagation systems)

"Indicator organisms" are microorganisms that do not pose a risk to the biological shelf life of the finished product, but do indicate that cleaning and disinfection measures have been carried out inadequately or that mistakes have been made during production (e.g. yeast culture in rinsing water and acetic acid bacteria in the bottling area).

Table 1 shows which microorganisms can be expected in which stages of production in the brewery.

In addition, reference is made to current and relevant literature that allows the further characterisation and evaluation of potential beer-spoilage bacteria, obligate beer-spoilage bacteria, indicator bacteria, foreign yeasts, yeast cultures and other microorganisms that are relevant to breweries.

Intermediate products such as fruit juice concentrates or sugar syrups indicate a high level of intrinsic microbiological protection due to their usually very low water activity (low A_w value) and high osmotic pressure (high Brix value). This means that predominantly osmophilic and osmotolerant bacteria are to be expected. Only a few can have a harmful effect on the product after re-dilution.

Volatile aging indicator substances are driven out of the sample through steam distillation. The ethanol distillate is adjusted to be alkaline and saturated with NaCl. The extraction of the aroma compounds is performed by shaking out with dichloromethane and the phases separated by centrifuging. The organic phase is further concentrated in a stream of nitrogen gas. Ammonia solution is added to remove the acids, as the acids would coelute, thus preventing the quantification of important substances.

This rapid test for softened water is carried out by means of indicator buffer tablets.

The pH value of boiler feed water is determined using a universal indicator.

The pH of boiler feed water is determined using non-bleeding pH indicator strips.