Producing a quality product consistently is the key to success! Every brewery has the capability of monitoring process and product to determine level of consistency and quality. Obviously a small brew pub will have a different level of quality control than a bottling microbrewery; however, the level of consistent quality should be the same.
Every brewery can and should monitor and evaluate critical points in the brewery. Basic record keeping is essential to establishing consistency and developing a basic QC program. There are three major points to controlling quality: Equipment, Wort, and Yeast Management.
Know your system and its limitations. Many brew systems have weak points that can potentially cause problems. Dead ends and shadow areas that do not receive adequate recirculation of chemical must be avoided if possible or must be manually cleaned and inspected. A consistent cleaning and sanitizing regimen must be followed. Documentation of the cleaning process and chemical usage rates are essential for consistency and to avoid confusion that could lead to inadequate cleaning.
It is important to work closely with your chemical supplier to be certain that you are using proper concentration levels, temperatures, and recirculation times. It is impossible to sanitize a surface that is not clean; all organic matter must be removed before sanitation can occur.
The term sanitized is not always well understood. Sanitized does not mean sterile. Good sanitation and sanitary practices lead to limitation of microorganisms but does not guarantee that they are eliminated. A smooth surface that has had all of the organic matter (such as dead yeast or wort residue) removed is relatively easy to sanitize because there is no protection or food for microbes. In contrast, a rough surface or a surface that has not been adequately cleaned is very difficult to sanitize because microbes are able to find protection from your chemical cleaning. Use of hot water as a sanitizer should be avoided. Thermophiles can survive high temperatures, so use of a no rinse sanitizer or a sanitizer followed by a sterile water rinse is essential.
In general, the most common sources of infections are heat exchangers, old cracked hoses, and deteriorating gaskets. Each of these locations offers cracks and crevices for microbes to take shelter in. Regular inspections of gaskets and any non-stainless surfaces are essential for consistent results. The heat-exchanger should be broken down and inspected at least every six months.
Knowing that your equipment is well maintained, clean, and regularly inspected will form the foundation to consistent, quality beer. In the event of a contamination issue, a well documented cleaning program will help to take some of the guess work out of determining the source of contamination.
Now that you are confident in your equipment, it is time to focus on your wort. If your equipment is clean and well maintained, it is relatively easy to produce stable and consistent wort.
Adequate record keeping will allow you to track the consistency of your wort. It is very important to monitor and record as many points as possible such as original gravity, pH, length of boil, percent evaporation, timing and quantity of hop additions, addition of any coagulants, and any other relevant data. Once again, if you have good, consistent records it becomes much easier to trouble shoot in the event of a problem.
It is important to keep track of raw materials that are used to produce your wort. Often, a change in beer flavor or yeast performance can be tracked to a change in raw materials, especially grain. A new shipment of grain can produce different nutrient and sugar profiles for the yeast as well as having a different level of soluble and insoluble proteins.
Wort must be boiled vigorously in order to achieve a proper protein break and to kill any possible infecting microbes present. An 8-10% evaporation in 1 hour is a good target to shoot for, but each brewery will have slightly different capabilities. Adequate protein removal prior to running in is important for beer stability and consistency. Use of kettle coagulants and a well designed whirlpool will aid in the removal of excess protein.
It is important that a brewer regularly check the stability of the wort produced. A very simple and effective method is a wort stability test. This test can be performed by any brewery with or without a lab. The wort stability test consists of aseptically pulling a wort sample (post heat-exchanger) into a sterile sample container and holding that sample for 3 days in a warm area. If the sample remains clear and no CO2 is formed, the wort is stable. If the wort clouds up, CO2 is formed, a film develops on the surface, or off aromas are detected, then you know that you have a problem. See the protocol section for complete instructions on Wort Stability Testing. In addition to stability, a brewer can also check the fermentability of the wort produced. A very simple and effective method is a forced fermentation test. This test can be performed by any brewer with or without a lab. The forced fermentation test consists of aseptically pulling a wort sample (post heat-exchanger) into a sterile sample container and inoculating with a very high yeast cell count (Dried yeast works fine). Agitate the container often. Check the gravity after 36-48 hours to determine terminal gravity. This test will give the brewer a good idea of where the fermentation should finish. If the main fermentation does not reach the same level as the forced ferment, the brewer will know there is a problem in the fermenter (pitch rate, temperature, oxygenation). If both the main fermentation and the forced ferment finish out of spec (too high or too low), the brewer knows that there is a problem on the brewing side (mash temperature, mash times, crush, ingredients).
Your equipment is properly cleaned and maintained, your wort is consistent and stable, now make sure all of your diligence and hard work are rewarded with consistent predictable fermentations resulting in great beer.
Yeast performance is tied to hundreds, if not thousands of factors. Everything that you do during the brewing process will have an effect on the yeast that are converting your sweet wort into beer. Once again, good record keeping on the entire brewing process will help to maintain consistency and to locate inconsistencies that could be causing a change in yeast performance or beer quality. Pitch rates and oxygenation were covered previously, but the importance of these two factors can not be stressed enough. Adequate pitch rates and oxygenation will help to minimize the impact of inconsistencies in the brewing process.
A brewer that does not have a lab must rely on his or her senses. Knowing the expected aroma, taste, and appearance of a healthy slurry will alert a brewer to possible deterioration of a culture. Fermentation tracking will also allow a brewer without a lab to maintain good, consistent fermentations. If your fermentations begin to take longer, lag times are longer, attenuation levels change, or flocculation character changes then you need to replace your culture. Ideally, a brewer should use fermentation data to determine the best time to replace a culture before there is a problem. If a brewer consistently sees the fermentation data begin to change at generation number 10, then the culture should be replaced at generation number 9. It is much less expensive to replace a culture than it is to dump a batch of beer down the drain.
For breweries with a laboratory, evaluating yeast is much easier. Essential testing consists of viability staining, cell counting, and plating for purity and strain consistency. With these tools at hand, a brewer can very effectively control the consistency of fermentations and the end product.
Documentation and Tracking
The importance of good documentation cannot be over emphasized. A microscope is not need to keep good records. Yeast information can be kept in a logbook or on computer file, which tracks all information pertaining to the yeast. For breweries without microscopes and QC programs, the need for tracking and documentation is just as important. The following are suggestions for documentation and tracking information.
- Strain ID and Generation
- Cropped from fermenter X
- Beer style, volume, date
- Temperature of fermenter at harvest
- Age of yeast at pitching
- Pitching quantity by weight or volume
- Pitching rate in cells/ ml
- Cell count on hemacytometer
- Viability by methylene blue or GenPrime Easy Count method.
- Trub removal and yeast dumps
- Sensory qualities of yeast (taste, smell)
- Lab results on yeast samples
Good fermentation records are valuable when evaluating yeast performance over a period of time. Brewing specs per batch:
- Wort cooling/ Run in time
- Sterile wort sample
- Wort aeration
- Fermenter volume
- Yeast pitching details
- Gravity and temperature daily
- Time to half gravity or set target (i.e. 5° P)
- Final gravity
- Cooling time and date
- Trub and yeast removal
- Forced ferment sample
Yeast Performance Variables
The number of times a yeast crop can be harvested and re-pitched will vary between strains and breweries. This is dependant on many variables. The more control the brewer has over these variables the more successful he will be in serial re-pitching the yeast.
- Yeast strain
- Yeast performance
- Age of yeast
- Storage conditions
- Yeast washing
- Sanitation- bacteria levels
- Stress: alcohol, CO2, pH, osmotic pressure, temperature and trub
- Yeast handling Harvesting technique
- Yeast growth during last ferment