Monday, October 7, 2013
You might be wondering why there hasn't been a blog post in a while. I've been focusing my efforts of the production of a "Brewing Engineering." A book to capture the last year of research that I have conducted. Over 200 pages and nearly 50 tables designed to simplify the brewing process.
It's available now!
Brewing Engineering is the culmination of extensive work done to understand how each part of the brewing process works. Understanding is developed into application and presented in a way that brewers can utilize, regardless of background. If you are a beer geek like me, I’m sure you’ll find reading about brewing science quite entertaining. If you are more of an artist, don’t worry: each exploration wraps up into practical application of the concept. If you have visited my blog, much of this information will look familiar. The most valuable posts have been included in this book. Each one carefully edited, and in some cases expanded on and even re-written. In addition, some of the information in this book you will not be able to find on my blog, or anywhere else for that matter!
Tuesday, April 16, 2013
Boiling and cooling priming sugar can be a pain. There are advantages to this, but how much does it benefit the beer?
A further analysis of why these steps are preformed might help derive a better processes. I think it is possible to retain all of the benefits of boiling and cooling priming sugar without adding any time to the processes.
The benefits are two fold. Boiling the water and priming sugar allows the sugar to dissolve more easily and kills any microorganisms that may have been introduced. Cooling it keeps the yeast from being killed by the boiling liquid, and also keeps off flavors from being added into the beer that would leached out by pouring boiling water into the plastic bucket. HDPE used for food grade plastic buckets is rated for temperatures up to 190°F.(1) Exceeding that temperature could leach unwanted flavors out of the plastic and into the beer.
Killing BacteriaMost bacteria can be killed by flash pasteurizing. (2)(3) Tap water contains very little bacteria to begin with because there is no nutrients. For bacteria to grow both nutrients and water are required. Dry sugar also contains very little bacteria because there is no water. Therefore the amount of bacteria that may need to be killed is small. Heating to 165°F or above for a minute or longer is sufficient for most brewers.
Not Killing YeastYeast will be killed nearly instantaneously if shocked with 165°F degree water, so the common thought is that the priming sugar needs to be cooled before adding it to the bottling bucket. While it is true that the yeast will be killed at 165°F, it's also true that the temperature drops very quickly as cold beer is added to the bucket. Yeast, like most bacteria, will thrive at 110°F. (However, It will produce off flavors if fermented for a period of time at that temperature which is why most ales are fermented at 65°F an bellow.) The beer will likely be about 65°F or cooler at the time of bottling. 1 half gallon of beer plus 1 quart of hot sugar water at 165°F will yield a combined temperature of 98°F.
The Processes1) Add your priming sugar and water to a microwavable container. I prefer a mason jar.
For the correct amount of water and sugar to use
so as not to change the ABV of the beer see this post:
3) Remove from the microwave, secure the lid and swirl to dissolve most of the sugar.
4) Remove the lid and place back in the microwave for another minute.
5) Repeat steps 3 and 4 until the sugar is dissolved, and the temperature is above 165°F
6) Start the siphon of beer into the bottling bucket.
7) Once there is aproximently half a gallon of beer in the bucket add the sugar solution being careful not to splash the liquids.
Monday, March 25, 2013
- 6.5 gallon Fermenttion Bucket
- Air Lock
- Bottling Bucket
- 1 Hydrometer
- 6 feet of 5/16" Vinyl Tubing
- Butterfly Capper
This is the kit I cut my teeth on:
What you'll need to round up
- Your spaghetti pot. (6 quarts is a reasonable size)
- Two cases of pop top brown beer bottles with a long neck and a skirt.
The three most common mistakes made by first time home brewers are:
- Lack of fermentation temperature control.
- Insufficient yeast.
- Use of tap water with extracts kits.
When choosing a kit look for one that uses dry yeast and has an ABV of 5% or less.
One packet of dry yeast contains about 150 billion cells. This is sufficient for up to a 1.050 starting gravity which is less than 7 pounds of extract in a five gallon (19 liter) batch. The result will be a beer less than 5% alcohol by volume.
Because extract is made from an all grain mash it has all of the minerals needed for the beer concentrated in it. The major manufactures, Briess and Muntons, both are located in areas that have great brewing water that already have enough minerals. By using tap water, or spring water you are adding extra salts that will end up leaving your beer with a kind of a twang. Use Distilled or Reverse Osmosis water for extract brewing. You should be able to find it for less than a dollar a gallon.
Step up your game
- Autosiphons ($10)
- Thermometer for measuring pitching temperature ($8)
- Kegging setup
These are the ones I have and they work great!
Making better beer and brewing toys.
- bin or cooler to use as a water bath for fermentation temperature control.
- Refractometer. Much easier, faster, and smaller sample size required.
- aquarium heater to ferment ale's in the winter
- scale for grain and extract
- scale for salts and hops
Wednesday, March 20, 2013
Yeast require oxygen in order to synthesize compounds during growth. The lack of oxygen will therefore become evident if the yeast are put in conditions that with adequate oxygen would produce large amounts of growth. In order to highlight the use of oxygen in these tests a high gravity wort will be used and drastically under pitched. If the free oxygen in hydrogen peroxide can be utilized by the yeast then this should make it evident.
The TestThe hydrogen peroxide solution at the pharmacy here is 3%. For each molecule of 2(HO) there is one Oxygen molecule that can disassociate. It takes two of them to make oxygen gas. With some molar math this means that the solution available at the drug store is equivalent to a 7000ppm O2 solution.
For the tests these will be diluted down to more reasonable amounts of oxygen. 350, 175, 88, 44, 22, 11, 5, 3 and zero will be used. Each test will be done in triplicate.
All tubes will be inoculated with a 21°P wort and 1 million cells per ml. (under pitching by a factor of twenty in a very high gravity wort.)
All tubes will be done in triplicate.
All of the tubes initial gravity, final gravity and final cell volume will be recorded. A cell count will be conducted on three of the tubes with the lowest volume of cells and three tubes with the highest volume of cells. From this information final cell counts will be derived for all 27 tubes.
In addition, daily cell counts will be preformed on two additional tubes. One containing no additional hydrogen peroxide and the other containing the 11ppm oxygen equivalent using hydrogen peroxide. Daily cell count and gravity will be checked.
The resultsHydrogen peroxide was effective at adding oxygen to the wort, but did not improve attenuation. The toxicity of the hydrogen peroxide was detrimental to yeast growth. The optimum level was an equivalent of 50ppm of oxygen although at this level the results were similar to adding no oxygen. The high gravity wort with low pitch rate took 12 days to complete with and without the added oxygen, although fermentation without added oxygen in the form of hydrogen peroxide was significantly faster.
Monday, March 18, 2013
The Practical Brewer has been an excellent resource for brewing. The chapters are all written by renowned member of the professional brewing community composed of both brewers, instructors and scientists. This is the best text book on brewing that I have read. Everything is covered in detail from wort production to fermentation.
If you are serious about brewing, whether as a home brewer or professionally, this is a book you'll want to have in your library.
Friday, March 15, 2013
Perhaps the title is a little far fetched, but this is entertaining and informative none the less. This feature length video makes for a nice way to unwind on the weekend. Take a trip through time to discover how beer has shaped civilization and led to numerous inventions.
Wednesday, March 13, 2013
The primary goal of fermentation is the production of alcohol, while the goal of propagation is increasing the yeast biomass. On one hand, anaerobic yeast respiration converts sugar into alcohol, carbon dioxide, and some energy. Aerobic reparation, on the other hand, converts sugar and oxygen into water, carbon dioxide and about twenty times as much energy. The real difference between these two is that with oxygen more energy is produced. Without oxygen more alcohol is produced.
The two things that yeast need from the wort to make new cells is material (sugar) and energy. While both of these are available during both aerobic and anaerobic respiration there is much more energy during aerobic respiration. This is why a stir plate, that provides constant oxygenation, is commonly used for starters.
Oxygen is good for propagation, but how much is required, and how can it be used to maximize cell growth?
Aerobic yeast respiration is as follows:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 31 ATP (see footnote 1)
180g C6H12O6 + 192g O2 → 264g CO2 + 108g H2O + 31 ATP
Converting from moles to grams we can see that for every gram of fermentable extract 1.07 grams of oxygen are required for aerobic respiration. For a 10°P (1.040) wort that would be a whopping 107,000ppm! With pure oxygen gas the saturation point of water is only 50ppm. So in terms of aerobic respiration, there is no practical limit to the amount of oxygen that can be utilized. Oxygen, however, is toxic to yeast in high concentrations.
Because oxygen is always in short supply anaerobic respiration dominates the metabolic activities. For this reason, the anaerobic reaction very closely resembles Balling observation. When the reaction is converted to moles it can be seen that the "losses" that balling describes are the sugar converting to other materials.
C6H12O6 → 2 CH3CH2OH + 2 CO2 + 2 ATP(see footnote 2)
1.9553g C6H12O6→ 1g CH3CH2OH + 0.9553g CO2 + 2 units ATP
2.0665g C6H12O6 → 1g CH3CH2OH + 0.9565g CO2 + 0.11g biomass (see footnote 3)
The Carbon Dioxide is virtually identical and the difference in glucose mass is almost exactly the yeast biomass.
If the two things that yeast need are sugar and energy to reproduce then how much more yeast would be generated from aerobic respiration. For every 2 units of ATP 0.11g of yeast are generated. If there were 31 units of yeast then 1.705g of yeast could be generated. This would require 3.6603g of sugar and adequate oxygen. Anaerobic respiration produces 0.053g of yeast per gram of fermentable extract. At 20 billion cells (dry mass) per gram that's 1 billion cells generated per gram of extract. Aerobic respiration could produce 0.4658g of yeast per gram of fermentable extract. This makes 9.316 billion cells per gram.
With adequate oxygen the yeast propagation could be almost 10 fold above what is typical of fermenting beer!
So how can we get anywhere near the 107 thousand parts per million, and what is the maximum the yeast can tolerate? Don't worry, I've got a plan and a set of experiments to prove it.
(3) Balling C. J. N. 1865. “Die Bierbrauerei” Verlag von
Friedrich Temski, Prague, CHZ. As cited in:
MODELING OF ALCOHOL FERMENTATION IN BREWING – SOME
PRACTICAL APPROACHES, Ivan Parcunev, Vessela Naydenova, Georgi Kostov, Yanislav Yanakiev, Zhivka Popova, Maria Kaneva, Ivan Ignatov http://www.scs-europe.net/conf/ecms2012/ecms2012%20accepted%20papers/mct_ECMS_0032.pdf
Monday, March 11, 2013
Out of the box the scale was accurate to 5%, but the scale can be calibrated with a 500g calibration weight.
One odd thing I noticed is that the scale seems to be fairly unstable at weights less than one gram. By shifting the substance on the plate the weight value will change by up to 0.2g. This is so small it shouldn't be an issue.
Overall, I think the scale is great, and an excellent value!
Friday, March 8, 2013
Take a trip with Sam Calagione to South America to discover how it is made now, and how it was made in the past.
Wednesday, March 6, 2013
YC-N : Yeast Calc (same as Mr. Malty) with "None" selected for Aeration
YC-SP : Yeast Calc (same as Mr. Malty) with "Stir Plate" selected for Aeration
S-04 : Fermentilist Safale yeast shaken only at the start of fermentation.
US-05 : Fermentilist yeast shaken only at the start of fermentation.
Balling : Karl Ballings observation applied to starters.
Wyeast : Calculator from W Yeast site
Wyeast : Calculator from W Yeast site
This data is a compilation cell counts on more than 50 starters. The lower inoculation rate starters have a higher spread of values. This deviation is likely error due to the smaller magnitude of cells counted. All starters were shaken vigorously at the onset of fermentation but otherwise left still.
When it comes to still starters, the easiest and most accurate way I have found to calculate cell growth is with simple multiplication, but if you have to use an online calculator then using the "intermittent shaking" selection seems to be the most accurate.
To calculate the number of cells to expect in a still starter the following eqation can be used:
Cells Grown = 10 * Volume of starter (in litters) * Gravity of starter (in degrees Plato)
Although only Yeast Calc is shown here the other two popular calculators have a similar growth curve. Mr. Malty is almost identical in results to Yeast Calc because the latter is a derivation of the former. The Wyeast calculator has a similar curve to the other two popular calculators.
Low Inoculation RatesOne thing that is most apparent when comparing measurements to the calculators is the performance at low inoculation rates. The calculators all show considerable roll off in growth at inoculation rates less than 20 million per ml. This could be due to time. The lower the inoculation rate, the slower the fermentation will progress. If the starter was used 48 hours after inoculation the cell count may very well be at the low levels shown by these calculators.
Moderate Inoculation RatesThe center portion of the calculators is very flat. For inoculation rates of 40 to 140 most of the curves are fairly flat. This fits well with what would be expected of normal fermentation. The primary limiting factor of cell division is available sugar making the cell growth directly proportional to sugar. Mr. Malty and Yeast Calc have setting for various types of aeration. Given more oxygen, yeast will preform aerobic respiration. (1) The larger amount of energy produced from aerobic reparation allows more bio mass to be generated. In the presence of high sugar concentration the production of biomass is the preferred. (2)
Cell growth is proportional to both sugar and available oxygen.
High Inoculation RatesAt high inoculation rates the calculators show diminishing return. This indicates that the yeast are reaching a maximum cell density. At cell density of 200 million per milliliter cell productions slows significantly. At a cell density of 300 million per milliliter cell growth nearly stops.
Sunday, March 3, 2013
Starsans, when properly prepared is a 0.08% phosphoric acid solution. (Think about the concentration. Even with just a trace of acid it is strong enough to kill nearly all bacteria) The pH of this solution is between 2 and 3 which is just about the recommended pH for yeast washing. If a small portion of yeast is combined with a much larger portion of star sans the pH will stay in the yeast washing pH range. If this yeast slurry with acid was added to the beer it would likely be noticeable sour. To prevent this, the acid can be neutralized.
Phosphoric acid not technical a strong acid although it is quite powerful with a pKa of 2.1(1). If this is combined with a small amount on a weak base the acid will pull all of the needed OH ions from the weak base to the point when all of the hydrogen ions have been cancelled. Because the ions to not disassociate easily from the weak base creating a solution that is too alkaline is not a concern.
Another advantage of using a stronger acid with a low concentration, That means the highest concentration of salts in also very low. One weak base that nearly everyone already has is baking soda, or sodium bicarbonate. This has a pKa of 10.3which is much closer to the neutral pH of 7. When sodium bicarbonate reacts, it breaks down into carbon dioxide and sodium hydroxide. Three salts can be formed from the combination of sodium hydroxide and phosphoric acid.(1) These are monosodium phosphate, disodium phosphate, and trisodium phosphate. These salts are fairly soluble in water, and will also be in low concentration. Crashing and decanting the yeast will remove a large percentage of this salt.
Recently I put this to the test. A slurry was selected that had low viability of 50%. It also had easily distinguishable bacteria. These were 15-20um long rods that stain with Methylene Blue. Two starters were prepared, one washed with Star San and the other was washed with water.
In summary, it looks like this is an easy way to truly wash yeast.
- Add equal parts slurry and prepared Star San to a container and allow to rest for one hour.
- Add a pinch of baking soda to the container to cancel the acid.
- Add DME and water to create a starter and ferment to completion.
Friday, March 1, 2013
- For reasonable inoculation rates and gravities cell growth is not a function of inoculation rate or volume. Cell growth is simply a direct function of sugar, and may be more accurately predicted by observing sugar consummation.
- Yeast taken from storage at 40°F (5°C) can out preform yeast taken from an active starter likely due to the glycogen content of the yeast.
- Attenuation is a function of both inoculation rate and gravity. Higher inoculation rates and lower gravities lead to higher attenuation.
GrowthCell growth observed over this wide range of inoculation rates and initial gravities showed cell growth proportional to the amount of initial sugar present. In the case of the active culture of S-04 7.2 billion cells were grown per litter per initial degree Plato. Considering that the average attenuation was 62% this indicates that 11.6 billion cells were grown per liter degree Plato of consumed sugar. This tracks very well with the daily observations. In a similar fashion the inactive starters grew 10.4 billion cells were grown per litter per initial degree Plato with an average attenuation of 68% making 15.3 billion cells grown per litter degree Plato of sugar consumed. Both of these starters closely followed the equations derived from Ballings observation for starter cell growth. Based on these observations the equation can be adjusted to account for the higher cell growth that is likely linked to proper aeration at the onset of inoculation.
Cells Grown = 14 * Volume of wort (Litters) * [Initial Gravity of wort (°P) - Final Gravity of wort (°P)]
GlycogenThe yeast taken from refrigeration outperformed the yeast taken from a starter in terms of total attenuation and in cell growth. When fermentation is allowed to run to completion yeast cells will build up a glycogen reserve. It is possible that this extra glycogen allowed the refrigerated yeast to grow more cells given the same amount of sugar. Further testing would be required to confirm this including measurement of the glycogen levels.
AttenuationThe percentage of sugar consumed seems to be a function of both the initial gravity and the inoculation rate. A linear fit for these two parameters shows an excellent r squared fit of 0.9139 and 0.9795. Although this shows wonderful correlation I am hesitant to say there is causation. There are a other considerable factors, such as temperature, that are not accounted for here. The equation also breaks down quickly at inoculation rates beyond the data set used. It does seem reasonable at inoculation rates and gravities typically used for fermentation of beer.
The following equation can be derived from the linear fits:
A = Real Attenuation (as a decimal. ie 0.71 = 71%)
G = initial gravity (in °P)
I = Inoculation rate (in million per ml)
A = 9.54E-4(G)-2.44E-4(G)(I)+4.23E-3I)+5.19E-1
Shaped markers are measured data points.
The number of cells at zero initial gravity is the inoculation rate.
The "Active" chart represents data taken from an active starter.
The "Inactive" chart represents cells taken from refrigeration.
Real Attenuation in %sugar by weight.
Each column is the number of cells used for inoculation.
Divide by 10ml for the inoculation rate.
Each column is the number of cells used for inoculation.
Divide by 10ml for the inoculation rate.
Wednesday, February 27, 2013
You'll see Sam Calagione founder of Dogfish head and his battles with Big beer. See the saga of Moonshot '69 as it was pushed out of the market.
Overall it was a great movie that made me want to go out and support craft brewing!
PS for those following the Side by Side Starters posts:
There are several applications of the data from the experiments which I am trying to condense, but this may be a few posts with the final results. So today is time to take a break from the numbers.
Tuesday, February 26, 2013
Testing Date: 2/25/2013
Total viable cell density: 50 million cells per ml
Thick Viable Cell Density: 1.2 billion cells per ml
Stress level: Low, Similar characteristic flavors to previous batch.
Bacteria level: Very Low, Sourness unlikely. (no bacteria visible)
Viability – Percentage of live cells of the entire cell population
Total Viable Cell Density – The number of viable cells in one milliliter of homogenized slurry.
Thick Viable Cell Density – The number of viable cells in one milliliter of settled cells such as those at the bottom of a starter that has been refrigerated.
Stress Level – A rudimentary assessment of cell health based on cellular morphology.
Bacteria – The percentage of visible bacteria of the yeast population
Other notes:This yeast was taken from a starter with a 1.040 (10°P) initial gravity wort made from DME. The yeast sample is very clean with very little protein trub. Viability was surprisingly low considering this yeast came from a starter. If the cell death was caused by freezing during transportation then the viable cell count could be as high as 125 million per ml (suspended yeast) , and 3 billion cells per ml (settled yeast)
Disclaimer:This report is an evaluation of the sample that was provided. There are no guarantees. The sample may perform differently than the slurry for a number of reasons that are beyond control. Care is taken to provide accurate results, however measurement error due to equipment tolerances, process, and calibration will create deviation in measurement from absolute values. This is not an evaluation of health or safety risks.
Monday, February 25, 2013
Observations of the daily collected data.
When looking at the daily collected data, the first thing that really jumped out was the correlation between sugar consumed and cell count. Sugar is known to be a limiting factor in cell propagation, but seeing how well the two correlated was surprising. This opens up a new way to look at yeast growth. Trying to determine cell growth solely from the input conditions is not using all of the data available. If in addition the final sugar by weight is used a much better approximation of cell count can be achieved.
Both of the test vials followed very close to producing 12 billion cells for every gram of extract consumed. Another way to look at that number is relative to volume. For each degree Plato the cell density increases by 12 million per ml.
Comparing the two
Both the refrigerated cells and the new cells started consuming sugar almost immediately. Both had reduced the sugar in the wort by half in the first day.
The daily data shows that the refrigerated slurry out preformed the cells removed from a starter. This was a second big surprise. Common brewing knowledge would indicate that cells that have been in the refrigerator for a month will be starved, and will not preform well, however quite the contrary was the case here.
This unusual performance may be linked to glycogen reserves. At the start of fermentation yeast will build glycogen reserves. During the growth phase these are significantly depleted during cell division. At the end of fermentation the yeast will rebuild these reserves as they prepare for dormancy. (1) The cells taken from the refrigerator were allowed to ferment to completion, and even after a month in the refrigerator still had significant glycogen reserves to support cell division.
It seems that it is better to allow a starter to run to completion than to use the cells at high krausen.
(1) Fix, Principles of Brewing Science, p97 in the 2nd addition
Saturday, February 23, 2013
To achieve the cell counts each slurry was counted and then varying volumes were added to the culture tubes. For the active yeast cells these ranged from 2 to 5 ml, and for the inactive culture they ranged from 1 to 4ml. Adjustments to gravity measurements would be needed because there is inherently residual sugar and alcohol in the slurry.
The array of gravities were achieved by diluting a 31.4°P wort and adding 1 to 5 ml. The remaining volume was filled with water to ensure each tube had 10ml of total volume.
The tubes were allowed to ferment for two weeks and then refrigerated and allowed to settle for several days. The height of the yeast cake in each tube was measured. Six cell counts were done and these were correlated to the heights of the remainder of the tubes to produce the final cell counts. A linear fit based on the number of ml of slurry was used to equate milliliters of slurry to number of cells. For this fit, the r2 value for the active culture was 0.9936 and the r2 value for the inactive culture was 0.9850
initial live cells