One important aspect of sample collection is that it must be correct or reproducible and representative. Another aspect is that the sample container is of sufficient volume or mass and well protected against environmental influences that change can alter the sample (light, temperature, outgassing, shaking, etc.).
wort, beer
The criteria of the respective analysis methods dictate how samples of wort and beer should be collected.
Special care must be taken when collecting a representative sample from a particular batch of wort, since it contains not only dissolved substances, but also those not in solution (e.g., hot/cold break material). If an entire batch of wort is in a single vessel (i.e., first runnings, lauter wort prior to boiling, cast-out wort retained in the wort kettle or pitching wort in the pitching vessel or fermentation tank), the contents can be thoroughly mixed, if necessary, prior to collecting the sample. If samples are to be collected from the wort lines, one must consider that the consistency of the wort can change through subsequent evaporation or dilution or that a concentration gradient can develop. For this reason, it is necessary to divert a small stream of wort into a sample collection vessel over the course of the entire cooling process, from which a composite sample can be collected after the contents have been thoroughly mixed.
The same procedure is recommended for collecting samples of green beer when transferring to a maturation tank or for collecting beer samples during filtration or centrifugation. One must also take into account that clarified and packaged beer has often been diluted with brewing liquor when pushing beer through lines or purging them of air. Moreover, beer can be mixed during changeovers and can often also be blended with beer from other batches.
Since the stability of wort samples is quite limited, the wort must be filled in sterile bottles and analyzed as quickly as possible. Any measures taken to increase stability, such as cold storage, freezing, pasteurization, chemical preservation (e.g., with 2-bromoacetic acid or toluene) and sterile filtration may only be employed if these processes do not alter the characteristics to be analyzed.