Thursday, November 29, 2012
Counting Yeast Cells to Assess Viability for Brewing
Pitch rates, as you have likely heard, are very important to creating the desired flavor profile in a beer. Pitching too much yeast will result in a bland lifeless flavor, while under pitching the yeast will result in hot alcohols and possible a stuck fermentation. Generally if you are within a factor of two of the target pitch rate the resulting beer will match your target.
How to count yeast cells with a hemocytometer.
What you need:
A microscope with 400x magnification
2 test tubes or small vials
A graduated 2ml volumetric pipette
A 250ml (1 cup) or larger container with a tight lid.
Methylene Blue (which can be purchased at a pet store)
Step one, making a stock 0.01% Methylene Blue solution.
Don't worry, you only have to do this once. Staining is used to distinguish the live cells from the dead cells. Methylene Blue is attracted to acids such as the deoxyribonucleic acid (DNA) in the yeast cell. Yeast cell have the ability to reject Methylene blue that has entered through the cell membrane. The result is that the dead yeast cells will stain blue, while the live yeast cells will stay clear. Because Methylene blue is toxic to yeast the concentration should be kept lower than 0.1%, and once the cells have been stained the should be counted within half an hour. When working with methylene blue keep in mind that it is a very dark dye that stains very well. If you spill even a drop you may have a blue dot on your counter forever. Methylene Blue sold to treat aquariums is typically 2.303%.
To dilute this to the 0.01% concentration that is recommended by White Labs (1)(2)
1) add 1ml of the 2.303% Methylene blue to the 250 ml container.
2) Fill the container with 230ml of water (230 grams, 7.77floz, 47 tsp, or 1 cup less 1 teaspoon)
Only 0.5ml are needed per measurement, so this container of stock solution that you have prepared will likely be enough for several years of testing.
Step two, preparing the sample.
With the hemocytometer you will only be looking at a tiny fraction of the yeast that you are evaluating, so it is important the the slurry is completely homogeneous before taking a sample. Every time a sample is drawn with a pipette it should be pulled up and dispensed three times. A pipette will hold 5% of the previous sample on its walls. Pipetting three times ensures that the sample is not diluted by the previous washing or sample.
1) Shake the container of yeast until the everything is completely mixed up. (If the slurry is not too thick a stir plate works great for this)
2) Shake the container some more.
3) using a pipette, remove 1ml of yeast from the slurry container. If the slurry has large particles it may block the pipette. If this happens you can use a drinking straw to remove the sample.
4) add the 1ml sample to one of the test tubes. The accuracy of this volume measurement will have a direct impact on the accuracy of your data.
5) add 19ml of water to the yeast to dilute the sample 20:1
6) mix the sample by shaking vigorously, or by drawing in and out of the pipette at least 10 times. Pulling and pushing the yeast through the small orifice of the pipette will break apart most floccs.
7) pipette 0.5ml of yeast from the sample test tube to the second test tube.
8) sterilize your pipette.
9) pipette 0.5ml of 0.01% methylene blue into the second test tube. Note that this dilutes an additional 2:1.
Step three, loading the hemocytometer.
1) place the hemocytometer on a paper towel and put the cover slip on.
2) mix the stained yeast with the pipette by pulling in and out at least three times.
3) remove a small amount with the pipette (you will only need about 0.1ml, or a fraction of a drop)
4) bring the pipette up to the hemocytometer without letting the tip touch.
5) dispense a hanging drop and touch the drop to the hemocytometer sample loading point. The counting chamber should be filled to the point where it begins to spill into the center overflow area. If some of the sample falls into the side spill areas that is okay, but these side moats should not be filled. If the center area has no sample in it the count will be low. If the side moats are filled then the count will appear high.
Step four, counting the cells.
If you haven't use a microscope before you might want to spend some time fiddling with the controls and doing some reading as to how to adjust everything properly. I was surprised by the number of adjustments on a modern microscope, and how crisp the image can be when you have everything adjusted correctly. There is a lot more to focus than just the focus knob! When you look at the cells you should note the amount of clumping. Clusters, or clumps, of cells indicate that the sample was not adequately mixed, and is thus an indication that your count may not be representative of the entire slurry. When focusing on the cells, tighten the diaphragm all the way. If the focus is too high you will see halos around the cells. If the focus is too low the cells will look blurry. Once the cells are in focus open up the diaphragm until the blue cells are clearly blue and the clear cells should still have defined membranes. If the diaphragm is opened too much, the cells will appear washed out and you may miss some in your count. Focus is important. It the focus is too high, the halo can make a dead cell appear alive.
1) Locate the upper left counting chamber. (This is called box 1)
2) Count and record the viable cells (clear) and the dead cells (blue).
3) Repeat this process with the upper right, middle, lower left, and lower right chambers
4) If you want to have an idea of your accuracy you can preform statistical analysis on these five data points.
Step five, calculating.
1) viability is the percentage of living cells.
v = total number of Viable cells counted adding all five boxes
d = total number of Dead cells counted adding all five boxes
viability = v / (d+v)
example: for v = 432 and d = 10
viability = 432 / (432+10) = 98%
2) viable cell density is the number of living cells per volume
df = dilution factor = 20
sf = stain factor = 2
vol = volume of boxes counted = 4nl x 5 boxes = 20nl
cd = cell density in billions of cells per liter
cd = v * df * sf / vol = v * 20 * 2 / 20
cd = v * 2
example 432 * 2 = 864 billion cells per liter
3) pitching volume is the amount of slurry needed to achieve your pitch rate
pv = pitching volume in ml
c = billions of cells to pitch
pv = c / cd * 1000
example: c = 200 billion cells needed to pitch
cd = 864 billion cells per liter
pv = 200 / 864 * 1000 = 231 ml (or roughly 231 grams)
There is a plethora of information available, but these are some of the best suited for this task that I have found:
A wonderful tutorial with pictures of what you should see while counting:
(1) Step by step procedure from White Labs:
Some more nice photos of what to expect and some bacteria that you don't want to see:
(2) Currently I am using 0.03% MB as it stains more strains consistently.
Methylene blue (Left) Test Tubes (Right) Left to Right are Alcohol, slurry sample, 20:1 dilution, stained sample, and water.
Tuesday, November 27, 2012
Starter Calculators Under a Microscope.
Quite a bit of work, especially recently it seems, has gone into ensuing that the correct amount of yeast is pitched to start fermentation. As a result, there are several calculator available for recommending how to build up the number of yeast cells required for optimal pitching rates. Considering the amount of work put into these calculators, the quality of their data sources, and scientific reasoning that has gone into their development, I expect that they are pretty accurate.
However, I would like to put the starter calculators to the test.
This proposed experiment will take two real world examples of yeast starters that would be typically produced for a five gallon batch of beer. Two different strains of yeast will be used, and each test case will be duplicated as an indication of test repeatability. Thereby making eight test cases. The size of the starter will be scaled down to make the test processes more manageable.
The two yeasts will be:
1) White Labs WLP566 Belgium Saison
2) White Labs WLP004 Irish Ale Yeast
The two target beer batches will be
1) 5 gallons of 1.050 wort
2) 5 gallons of 1.080 wort
Typically, a starter is created by adding a vial or pack of 100 billion cells to a 1.035 wort. The volume of the wort is used as the variable to control the number of cells produced.
The recommendations from three popular calculators are summarized here:
Mr. Malty and Yeast Calc are very close to each other in estimations, which we can expect, as both of them use the same set of data to create their calculations. The average starter size for the 1.050 wort is 1.0 liters, and for the 1.080 wort is 3.2 liters. These will both be scaled, keeping the same inoculation rate, to 750ml to make the test more manageable. The small starter will be 75 billion cells in 750ml, and the large starter will be 23 billion cells in 750ml.
The starters will be shaken for 40 seconds immediately following the pitching of the yeast to ensure adequate aeration and yeast suspension. The starters will be inverted every 12 hours to suspend the yeast. They will be allowed to ferment for 48 hours at ambient room temperature of approximately 68 degrees. After 48 hours the contains will be agitated to suspend the yeast and the cells will be counted on a hemocytometer.
Post a comment if you are interested in seeing the results of this experiment.
Post a comment if you are interested in seeing the results of this experiment.
Sunday, November 25, 2012
When has my beer finished fermenting?
The common wisdom is that your beer has finished fermenting when two gravity readings are the same two or three days apart. While this is true for most beers it is not quite be accurate for high gravity long fermenting lagers. Also light high hoped ales you might want to get into bottles sooner rather than later to preserve the hop flavor. Contrary to the common mantra, longer fermentation time is not always better. If the fermentation temperature is bellow 60 degrees the beer may benefit from being warmed to about 70 degrees after the initial fermentation is complete. This is called a diacetyl rest.
So where does the "two consecutive readings" rule come from?
A typical hydrometer can be read repeatably to one gravity point. Also, one gravity point of sugar will add about 1 volume of CO2 to the beer. So two consecutive readings will indicate that you are within one point of final gravity. If you carbonate your beer to 2 volumes of CO2, the worst case would be a product carbonated to 3 volumes of CO2 which is still a reasonable amount of
carbonation. This is a very reasonable rule to follow, but the time between the readings is a variable that can be addressed to better indicate when the beer is done.
Then ... how many days should be used between readings?
There are two main variables at work here. The beer's original gravity, and the fermentation rate. The original gravity is easy to determine, but there are a plethora of conditions that effect fermentation rate. The goal is to determine when the beer is within one point of final gravity. The fermentation rate itself is an unknown, but we do know that it will roughly follow a logarithmic rate. Another way to think about this is that each day a percentage of the remaining sugar will be converted to alcohol. Each day there is less sugar, so
the rate decreases with time.
In this plot of gravity vs time notice that the gravity continues to fall indefinitely even after one point of stability is reached at day eight. Also note that in this case the gravity would have been incorrectly read as stable if measurements on days 6 and 7 were used. For this case readings two days apart would be adequate.
Crunching the numbers you can come to this same conclusion, but the following table shows how many days apart readings should be taken based on the initial gravity and number of days from the start of fermentation.
Gravity = OG * exp(-tou * t)
Gravity is the number of gravity units above final gravity
OG is the original gravity (corrected for final gravity)
tou is the fermentation rate in percent per day
t is the time in days.
readings can be taken 1 day apart until day 10 of fermentation
readings should be taken at least 2 days apart until day 20 of fermentation.
readings should be taken at least 3 days apart until day 25 of fermentation.
readings should be taken at least 4 days apart until day 30 of fermentation.
readings should be taken at least 5 days apart until day 40 of fermentation.
readings should be taken at least 7 days apart if the fermentation continues longer than 50 days.
Saturday, November 24, 2012
Beer and Chocolate Tour of Beacon Hill and Back Bay (Half Off)
Beer and Chocolate! I love them both, you can't go wrong with this one.
Choose Between Two Options
- $25 for a Beer and Chocolate tour for 1 person (a $50 value)
- $280 for a private Beer and Chocolate tour for 10 people (a $560 value)
Friday, November 23, 2012
Basic Water Chemistry
Water ion composition is one of the more subtle ways to fine tune a beer, but if used in excess they can also make your beer unpalatable.
Keeping it simple will keep you out of trouble. In most of the United States tap water has a fair amount of sulfates, too much sodium and chlorine for most beers, and very little calcium. Mash enzymes need calcium to work effectively, and it is a vital nutrients for yeast. The challenge with this water is therefor boosting the calcium level without overloading the other minerals.
Boston tap water (used for Sam Adams Beer) has the following mineral profile:
Ca 4 ppm
Mg 1 ppm
Na 32 ppm
Cl 23 ppm
The overall hardness (or total dissolved solids) is low which allows it to be built up. If your water is hard (above 120ppm CaCO3) then you will probably want to use reverse osmosis water.
CaCl (Calcium Chloride) will make beer sweeter. For making a beer that has some malty sweetness to it Add 1/2 a tsp of Calcium Chloride to your grains for a 5 gallon batch of beer. This will add 49ppm calcium and 86ppm chlorine.
CaSO4 (Calcium Sulfate or Gypsum) will bring out the hop bitterness. For pilsners, lagers and light ales add 1/4 tsp Gypsum. For a middle of the road ale add 1/2 tsp. For Stouts add 3/4 tsp and for IPAs and other hoppy beers add 1 tsp.
CaCO3 (Calcium Carbonate or Chalk) for a dark beer that you want to add some mineral water qualities to add up to 1 tsp of Calcium Carbonate. Unlike the other brewing salts, chalk will raise the pH of the mash water, however most of the time the pH needs to be lowered in the mash to achieve optimal pH levels.
You can make it much more complicated that this if you want, but these basics should give you a starting point for fine tuning your beer.
Wednesday, November 21, 2012
Amscope Binocular Compound Microscope
The Amscope Biological Binocular Microscope is everything I thought it would be. It's not nearly as nice as my brother's professional Olympus, but for the money, the Amscope can't be beat. The microscope comes with just about everything you would expect and then some. There is oil for the immersion lens, and two color disks to improve resolution when using the higher magnification settings, and a spare bulb. One thing that I was pleasantly surprised by is that not only can the width of the beam of light be adjusted with the diaphragm, but the condenser lens for the lamp can be focused. The combination of these two adjustments can create very crisp images at the dry 400x power, and the 1000x oil immersion is even more clear!
A couple of things I learned the hard way about microscopes. 1) Especially at higher magnification cover slip thickness is important to image quality. 2) with oil immersion the cover slip must be very thin. If the cover slip is too thick then the lens will not be able to get close enough to the cover slip to focus. These objectives are designed to work with 0.16mm cover slips, also known as a #1.5H
The optics are good, but not great. If you want a clear image above 1000x then you will likely need to spend several times more money on a professional scope. The 20x eyepieces work fairly well, but the resolution is only slightly better than with the same objective and the 10x eyepiece.
For counting yeast cells this scope is more than adequate. I am happy with my purchase.
First off let me say that these photos don't do the microscope justice. It is much more clear when I was looking though the lens of my scope. These photos were simply taken by holding a cell phone up to the eyepiece. Unfortunately in my nice camera, the sensor is too far back in the body to work with this technique.
The blue cells are dead yeast cells that have absorbed the 0.2% methylene blue solution. It seems that even a 0.01% solution of methylene blue will work for counting viability, but a few minutes of incubation is required. With a 1% methylene blue solution the cells could be counted almost immediately, but some of the live yeast cells seemed to be having trouble rejecting the dye. The White Labs recommendation of 0.01% is what I will likely be using from here on out.
In the picture below and to the left, the sausage shaped cell is likely a bacteria. Luckily this was a rare find when looking at my yeast.
(Click on the images to see them in full resolution)
In the image on the right a different type of bacteria can be seen. It is about 5 microns long and you can just make out the filament and the body.
Posted by Unknown at 11:30 AM 1 comment:
Monday, November 19, 2012
Fruit The Easy Way
While adding fruit directly to the secondary fermenter may an easy way to get it into the fermenter, it makes it difficult to separate it from the beer later. The times that I have done it this way my bottles have always ended up with some pieces of fruit in them. While the fruit chunks are not any sort of hindrance to the flavor, they are certainly not appealing to have floating around in your glass.
Frozen fruit is an economical choice, and has additional benefits to fresh fruit as well. The freezing processes breaks down the cell walls allowing more of the fruit flavors into your beer. In addition, contamination is less of an issue because cold temperatures inhibit bacteriological growth. Although some people add frozen fruit directly to the fermenter I wouldn't recommend it for two reasons. First, the cellulose of the fruit will release the juice into the beer, but it will be replaced by beer in the processes. I have had as much as 33% trub loss because of this issue. Second, floaters.
The best way I have found to add fruit to your beer is to pasteurize the fruit. Not only does this processes remove almost all of the cellulose, but it will also kill any bacteria that may have somehow made it to this point.
1) Add the frozen fruit to a sauce pan.
2) 1 pint of water for every pound of fruit.
3) Apply medium high heat to the sauce pan stirring constantly and mashing. (A potato masher works great for this)
4) Once the temperature has reached 160 degree turn off the heat.
5) Pour this mixture through a sanitized mesh strainer and into a second sanitized container and affix the lid.
6) Allow this to cool for about 20 minutes and then move it to the refrigerator.
7) After several hours in the refrigerator pour the contents into the fermentor.
This is more work on the front end, but it will save you work on the back end trying to separate beer from fruit. And, more importantly, it will yield a few more bottles of beer!
Saturday, November 17, 2012
Christmas wish list for homebrewers
Homebrewing is a wonderful hobby, and with it come lots of toys. Some make better beer, but lets face them just add that bling factor to our rigs.
This list of brewing equipment is the best I have found organized from low to high cost to make it easy to shop for the brewer on your holiday shopping list.
Brew Bag -
This stocking stuffer will make any brewer happy that is looking to start all grain. The 5 gallon paint strainer bag will fit most brew kettles, and can be reused. If you are handy with a sewing machine I would recommend making one, but if you have two left thumbs when it comes to needle and thread this is the best alternative I have found.
The Auto siphon -
If you don't have one of these, get it. It was a night and day difference when I switched over from traditional racking method to an auto siphon. With a few quick pumps the beer will be flowing from one container to the next. It's much less messy than using tubing by itself.
16 qt brew kettle -
If you are brewing stove top, it will be difficult to boil more than 4 gallons of water, so the 16 qt pot is the perfect size. For the brew in a bag (BIAB) method this allows for up to 10lbs of grain to be used in the grist making it possible to produce beers up to 5% ABV in a 5 gallon batch, and up to 8% if a 3 gallon batch.
10 gallon cooler -
This is on my wish list. This can serve a dual purpose as a swap cooler and a mash/later tun. As a swamp cooler it will hold cold temperatures during the summer months to tightly control ales, and keep drastic, beer damaging, temperature swings minimized during the winter months for producing lagers. As a mash and Later tun the isolation will help maintain the single degree of control needed to mash grain. For use as a later tun, the valve can be converted for about $20 in parts.
Or get it already converted!
Thursday, November 15, 2012
Top ten ways to restart fermentation
Okay, so you've read through the top ten reasons why your final gravity might be stuck, and it really is. Don't loose hope here are the top ten ways to fix a stuck final gravity. These can even be combined to better restart your fermentation.
1) Give the fermentor a swirl.
Try the easy things first. You might be able to squeeze a few more points out of the fermentation by gently coaxing the yeast back into suspension.
2) Move the fermentor to a warmer area.
Fermentation temperature can change attenuation by about 2%. That might be enough to get over the line from cloyings to malty.
3) Repitch with a higher attenuating yeast
For ciders and wine, champagne yeasts, such as EC-1118, will ferment simple sugars to completely dry. For beer, Safale S-04 is also a great high attenuating yeast. At this point in the fermentation the flavors have already been added by the beer yeast, so adding this second yeast will not impact the flavor much. If the fermentation has stopped significantly short of what was expected it could be caused by a combination of under pitching and under aeration. In this case mix the yeast with one quart of water and aerate well by shaking the container until there is a think foam on top of the slurry.
4) Add simple syrup.
Sometimes the yeast needs a little kick in the pants to get going. If you are adding yeast, then it's easy to add a little extra sugar to make sure the yeast starts up.
5) Add yeast nutrients.
Especially if the beer was under pitched the yeast can run out of nutrients. It takes special proteins for yeast to convert long sugar chains found in malt extract and worts generated from high mash temperatures. The yeast nutrients will give the yeast the proteins that they have depleted.
6) Add beano
Beano from your pharmacy, or amylase enzyme from your homebrew store, will break the longer sugar chains into shorter ones. So if the yeast in the fermentor cannot digest the long chains this will help them continue their job of conversion. The only problem I have heard with this is that it works too well. You may end up at 1.000. 1/2tsp is a good starting point for a 5 gallon batch.
Other ways to fix the high final gravity without restarting fermentation
7) Dilute the beer
A final gravity of 1.020 will taste pretty sweet, but if diluted to 1.015 it might not bee so bad. The hop bitterness and the flavor will also be diluted, making it a different beer, but this may make it drinkable.
8) Add hops
A little bit of bitter will balance out the maltyness. You could add a couple of ounces of hops right into the fermentor to dry hop the beer, or make a hop tea. Either boil the hops in a approximately a 1.020 wort for 30-60 minutes to get some bitterness, or steep them for about 10 minutes in water to just get the earthy flavor.
9) Add fruit
If it's already sweet, then run with it. Fruit, by itself, is sour in beer because most of the simple sugars that they contain are fermented into alcohol, so having some malty sweetness will make a beer that the lady folk will love.
10) bottle it.
If all else fails, or you decide to leave it for other reasons, change the style name. Maybe the recipe was for a Porter but now you have a Dunkel. Maybe your American Lager is a Bohemian Pilsener.
Tuesday, November 13, 2012
Yeast pitch rates can greatly effect the beer produced. Even a factor of two can be significant. (1) There are several calculators available that can be used to determine the amount of a slurry to pitch, and the volume of a starter. (2)(3) Recently I used one of these calculators, entering the harvest date of the yeast, the thickness of slurry, and several of other factors. In order to pitch the 125 billion cells for the beer I was brewing the calculator indicated that I would need 7.5 oz of my slurry.
What I have found recently is that the calculator I used deviated from cell counts by more than a factor of 10!
Last weekend I spent some time with my brother, a microbiologist, looking at some of the yeast cultures that I have collected, and did some cell counts to determine density and viability. There were a few ounces of the same slurry that I didn't pitch, so we took a look at it to see how close the calculator came to estimating the number of viable cells. We found that the slurry that I though was 16% viable based on the collection date was actually 60% viable, and the cell density was not 400 billion cells per liter, but rather 2000 billion cells per liter. The result was that I had pitched almost twenty times more cells than were required. As you might expect the fermentation process was ridiculously fast and it reached the final gravity in less than 24 hours. I'll leave this one to sit on the yeast cake for some time to clean up after that crazy party.
So far, from the data I have collected, it is hard to correlate viability to harvesting and storage techniques. However, with a microscope and a hemocytometer, this is really a pretty simple task to count viability. My first time counting cells went pretty quickly. We measured viability and counted cell density of four slurries in about an hour. If we had all the materials in the right place, and with a little practice, I image this could be a 5 minute job. So far it looks like the best way to know how much yeast is being pitched is to count the cells.
Sunday, November 11, 2012
How to calculate fermentation time
Most brewers will tell you that it can't be calculated but will yield that for a known recipe and know fermentation conditions it can be approximated. However, I think with sufficient data the date of completion can be calculated and the final gravity can be calculated within half a gravity point.
Yes, to the day, and within 1.0005 of the final gravity.
Measurements of fermentation of several beers I have brewed show that if fermentation temperature is maintained that the fermentation rate is exponential. Using data from three measurements and an exponential fit the data matches very well. The main source of error is the resolution of the hydrometer which is very accurate, but can only be read to about one gravity point. The second source of error comes from fermentation start. If the fermentation is slow to start then the original gravity and pitch time cannot accurately be used as the first point of the data.
Putting it to practice.
I brew and bottle on Friday or Saturday. So best case would be I would brew a nice hoppy pale ale that I want to preserve the hop flavor of, then bottle the following weekend. The days in between can be used for data collection. If I measure the specific gravity 24 hours from the pitch, then on the following Tuesday and Thursday there is sufficient data to preform an exponential fit.
The basic steps are as follows:
1) Record the specific gravity, date and time of three days.
2) Enter the data into excel. Add a column for the number of days from the time of pitching the yeast. Add a column for the specific gravity less the final gravity.
3) Add an exponential trend line for the new columns that you have created.
4) adjust the final gravity until the best fit R squared value is achieved (as close to 1 as possible)
5) add a column with the equation that has been derived and plot the subsequent days.
6) The day that the new equation drops below 1 is your beer is ready to bottle.
7) check the gravity of the beer on the day that you have found and it will be on the money if you did everything right.
Friday, November 9, 2012
How much hops are enough?
Beers, as described in the Beer Judge Certificate Program (BJCP) style book, range from none to a puckering 120 International Bittering Units (IBUs). Some number crunching (standard deviation, and mean average) break these numbers down into some categories:
Lightly Hoped: 0-15
Moderately low hops: 15-25
Moderately high hops: 35-45
Highly hoped: 45 and up.
My preference is in the moderately low range, and my wife prefers lightly hoped beer. It's a fairly simple processes to find the range you like and calculate how much hops to use to achieve that same bitterness level. This can easily be done with various calculators found on the Internet.
However there is more to hops than just the bitterness level.
Over time as a brewer you will get a feel for the amount of bittering, flavor and aroma hops you prefer in a beer, but without that experience there is no way to really qualify or quantify what a beer may taste like given a recipe. In "Designing Great Beers" By Ray Daniels he gives a wonderful explanation of they wide variety of factors that play into flavor and aroma, compared to the relatively simple reaction the creates bitterness.
One simple way to quantify the type of bitterness the hops may add is to break them into two groups. Bittering and Flavor. Hops added early in the boil, spending more than 25 minutes in the kettle, will add mostly bitterness. Hops added later in the boil, spending less than 25 minutes will add mostly flavor. The ratio of bitter IBUs to flavor IBUs can be a way to compare recipes.
4:1 - mostly bitter.
2:1 - balanced.
1:1 - mostly flavor.
You'll also develop a sense of flavor for the various hops. My personal favorite is Challenger. It works wonderfully as but a flavor and bittering hop. Taste is very subjective, but if you keep this in mind with your brews you will be able to better evaluate hop schedules in recipes and better formulate your own recipes.
For more details on this subject this is a wonderful resource:
Wednesday, November 7, 2012
Top ten reasons why your final gravity is stuck
Top ten reasons why your final gravity is stuck
1) Using a refractometer to measure final gravity.
Refractometers seem to be the flashy new toy that every home brewer wants to have. They allow fast measurements of the wort or beer with a sacrifice of only a few drops of beer. However, this tool, if not used correctly, and indicate an inaccurately high final gravity. Alcohol will skew the readings. The refraction index of alcohol is different than that of water, so it must be compensated for when taking a measurement. There are several calculators available online that can compensate this for you.
2) Using extract
Not all malt extracts are created equal. Studies have shown that some extracts are as little as 55% fermentable. Ray Daniels provides a wonderful description of this in his book "Designing Great Beers"
3) Not waiting long enough between consecutive FG readings
One day apart isn't always waiting long enough. Beers that have taken longer than 10 days need to have consistent reading 2 days apart to ensure final gravity is reached. There is a whole blog post on this subject.
4) Using a hydrometer that is inaccurate
It's very easy to knock a hydrometer out of calibration. I used to be in the habit of just dropping it back in the tube. Eventually I started getting some readings that didn't make sense. I check the hydrometer in water and it was reading 1.005! Lightly dropping the hydrometer can move the paper inside and change the adjustment.
5) Mashing at a high temperature
Each degree above 152 causes 2% less attenuation. There is a whole blog post on that. http://woodlandbrew.blogspot.com/2012/10/mash-temperature-and-thermometers.html
6) Using an inaccurate thermometer to measure mash temperature
If your thermometer reads 150.0 it doesn't mean it's accurate, in fact it could be off by 5 degrees putting you at 155. Also, regardless if it is new, you paid a lot of money for it, or it being analog doesn't mean it's accurate. Check it in boiling water to make sure it will be close at mash temperatures.
7) Mash time too short.
Even after conversion from starch to sugar is complete the beta enzymes will continue to break down the long sugar chains into shorter ones. Mashing at 150 for 60 minutes will produce a less fermentable mash than mashing at the same temperature for 90 minutes. To control your wort's ferment ability you will want to add a mash out step at 165-170 to denature the enzymes.
8) Over use of Campden tablets
If you have highly chlorinated water you might be using Campden tablets to rid your water of free chlorine. Campden may be good at removing chlorine, but it also acts a yeast inhibitor. In fact, it is commonly used in wine and cider making to stop fermentation. Using 1 tablet per 20 gallons will reduce the chlorine and not impede the yeast much.
9) Under pitching yeast, not oxygenating well and not adding yeast nutrients
A combination of two of the three will cause the yeast to run out of nutrients and may lead to a stalled fermentation. Yeast require specific proteins to break the longer sugar chains into short chains that they can convert to alcohol.
10) Fermentation temperature
Colder fermentation temperatures are more likely to add to a stalled fermentation, although in my experience, this is rare. rousing the yeast by swirling the fermentor, warming it to 70 degrees and adding corn sugar and yeast nutrients can get it going again.
Monday, November 5, 2012
The Homebrewer's Garden Book Review
For my birthday, my wife got me "The Homebrewer's Garden." As far as books on homebrewing goes, this is one of the most usable books that I have in my library. The authors, Joe Fisher and Dennis Fisher, Add just the right amount of description to make the information clear, but they leave it concise enough that you don't have to go digging to find what you are looking for. This book brought to mind things I wanted to try with every page I turned.
There are forty pages of information on growing hops in this book. It's all the information that I will likely need all rolled into one convenient spot. I'm really looking forward to ordering some Risomes March. Here in Malden it gets rather cold, and there are quite a few trees, so it looks like I'll be ordering Nugget and Ultra.
The reason I wanted this book was for the section on growing hops, but the following sections are equally intriguing. There are full page profiles of every herb I have though about brewing with and then some. The section on homemade malts is something I am looking forward to as well. By making you're own specialty grains you are essentially getting them at the cost of base malt, and they are much more fresh that you could possibly buy!
The recipes in the back look very adventurous showing use of juniper berries and elder flowers and over a dozen other spices I have never used in beer.
If you have even a moderately green thumb, and have a little space for a garden, then I highly recommend this book. It also serves as a reference on how to use some unusual ingredients in beer making.
Saturday, November 3, 2012
To properly lager a beer the fermentation temperature needs to be near 50 degrees for the
first two weeks of fermentation. Many home brewers have dedicated refrigerators, some with temperature controllers, or other more elaborate setups to accomplish this. A swamp cooler with bottles of ice is also an alternative that some home brewers use. As was seen in the data collected for my previous post on swamp coolers, without insulation the ice will melt in less than an hour, and the temperature will climb back up to the ambient temperature over the course of about 12 hours. This is adequate when the goal is to ferment about five degrees or less below the ambient air temperature, but for lagering this might be a stretch. I don't know about you, but my home isn't kept at 55 degrees in the winter.
The average temperature outside, however, could be at the lagering temperatures for several months throughout the year depending on your location. Here in Malden, Massachusetts the average temperature is between the lagering temperatures of 48 and 58 for four months. April and May in the spring, and October and November in the Fall.
So the question is, what will happen when the swamp cooler is brought outside?
Previously the Tou or temperature-coefficient of my system was found to be 0.136 degrees. That number didn't mean much to me until I thought further about it. In the equations used before Tou is the amount of energy that the system absorbs from the outside per hour. This means that 13% of the heat from the outside system is absorbed by the fermenter, and 87% of the heat in the fermenter is contained. Using this we can model the reaction of the swamp cooler for a non-static temperature using an iterative processes.
In the graph at the top of this post the blue curve is the outside air temperature. the red curve is the modeled temperature of the swamp cooler. Most of the numbers in column F are fairly self explanatory except for perhaps the "hold%" This is the amount to temperature that the swamp cooler "holds" from the previous hour. Each cell in the wort column is equal to 87% of the previous temperature plus 13% of the outside air temperature.
Will it work? I really don't know, but it looks like I'll be lagering soon!
Thursday, November 1, 2012
UFO Raspberry Hefeweizen Clone Recipe
Give this a try and tell me what you think. It's a house favorite!
Batch size: 2.5 gallons
Style: 20 / 16A Fruit Witbier
Recipe type: All Grain
2lbs American 2-row
3lbs Wheat Malt, Light
2 oz American Caramel L 40
8 oz rice hulls
1oz of Hallertauer
1/4 tsp CaSO4 (Gypsum) to bring the SO4 level to 65ppm
1/4 tsp CaCl (Calcium Chloride) to bring Cl level to 136ppm
Protein Rest at 122°F for 15 minutes
Saccharification Rest at 152°F for 60 minutes
1oz of Hallertauer for 60 minutes.
80 Billion cells of Safale - US-05 American Ale Yeast
Swamp cooler at 68 degrees for one week
Pasteurize 4lbs Frozen Raspberries, cool then add and ferment until final gravity is reached.
Strain when racking to bottling bucket.
Prime with 3 oz of corn syrup dissolved in one cup of water.
Condition for two weeks at room temperature then move to the refrigerator for one week.
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