We’ve all heard it. I’m ashamed to say that I’ve even parroted it myself in the past. But it’s only half true.

The OG contribution of simple sugars is certainly easy enough [...]]]>

A pound of sugar per five gallons of beer will add nine points to the original gravity and reduce the final gravity by two points.

We’ve all heard it. I’m ashamed to say that I’ve even parroted it myself in the past. But it’s only half true.

The OG contribution of simple sugars is certainly easy enough to calculate. Most brewers are probably aware that potential extract is typically given as a percentage of the potential extract of pure sucrose (46.21 point-gal/lb, 96.39 °P-L/kg). Let’s assume a volume of 20 L (5.28 gal) just to make the math easy. For a 5.0-5.5 gal batch volume, that will get us within 5%, which I think most brewers would concede is “close enough”.

(96.39 °P-L/kg)(0.454 kg)/(20 L) = 2.19 °P = 1.00856

So if your batch volume is 5.5 gal, eight points might be a better rule of thumb, but the oft-quoted value is essentially correct.

Determining how sugars will affect the FG gets a little more complicated, because, let’s face it, for most of us it’s been a while since high school chemistry. There also has to be an assumption made about how much of the sugar is consumed, and how much is fermented. I think it’s reasonable to assume that a healthy, active population of yeast will consume nearly all of the simple sugars available. I’m going to further assume that the sugar is being added during the anaerobic fermentation phase, so that nearly all of it will be fermented, as opposed to being used for aerobic respiration. The amount of ethanol generated then becomes a simple question of stoichiometry. The relevant reaction is:

C₁₂H₂₂O₁₁ + H₂O → 4C₂H₅OH + 4CO₂

So four moles of EtOH will be produced per mole of sucrose fermented. On a volumetric basis:

4((454 g)/(342.3 g/mol))(44.01 g/mol)/(0.789 g/mL) = 295.9 mL

Which is 1.458% ABV, incidentally. The reduction in density is a two-term weighted average:

(20000*1.0000 + 295.9*0.789)/(20000 + 295.9) = 0.9969

So when added to 20 L of water (or beer), a pound of fully-fermented sugar will actually reduce the SG by about 3.1 points, or 0.78°P. Maybe I’m splitting hairs here, but saying “two points” is off by more than 50%.

Last time I toyed with the idea of “reverse mashing”, I found that an unheated kitchen isn’t a great place to do mashing experiments in the winter. Fortunately, I have a new toy available in the form of an oven with a “Warm” (170°F – 77°C) setting, and so I was able to perform two [...]]]> Background

Last time I toyed with the idea of “reverse mashing”, I found that an unheated kitchen isn’t a great place to do mashing experiments in the winter. Fortunately, I have a new toy available in the form of an oven with a “Warm” (170°F – 77°C) setting, and so I was able to perform two additional mashes utilizing longer rests.

Experimental Setup

For details on how the experiment was conducted, refer to the first post on the subject. Once again, the reverse mash was performed first, to determine the overall length of both mashes. Total time was 100 minutes, and the temperature profiles for all four mashes are shown below.

All other variables were kept constant between the two sets of mashes, with the exceptions of size and fermentation temperature. Since I needed starter wort for some upcoming brewing, I doubled the size of the mashes, to 1000 g of grain each. Fermentation took place in my new fermentation chamber, with the air temperature set for 20°C ± 1°C. The test worts were allowed to ferment for six days, then rested for one day at 8°C before gravity readings were taken.

Results

The reverse mash fermented from 12.0°P to 1.0093 SG, and the control from 12.4°P to 1.0068. As expected, the conventional step mash exhibited both higher efficiency and higher attenuation than the reverse mash. While the efficiency values for both new mashes are significantly improved, however, the attenuation values are similar. While increasing mash efficiency is desirable in most situations, home brewers may well find that a very short step mash provides fermentability on par with a more conventional longer mash, and that the time savings outweigh their comparatively modest financial investment. In a commercial brewing setting, however, the traditional lengthy mash with α- and β-amylase rests is clearly the better option.

The last time I published the results of some dry yeast viability testing, I made the assumption that the reduction in viability that resulted from rehydrating the yeast in wort rather than water would have flavor impacts similar to under-pitching a liquid yeast culture. Shortly thereafter, James Spencer of Basic Brewing and Chris Colby of [...]]]> Background

The last time I published the results of some dry yeast viability testing, I made the assumption that the reduction in viability that resulted from rehydrating the yeast in wort rather than water would have flavor impacts similar to under-pitching a liquid yeast culture. Shortly thereafter, James Spencer of Basic Brewing and Chris Colby of BYO Magazine threw down the fungal gauntlet by soliciting home brewers’ tasting results using dry yeasts, and I decided to take the additional step of actually fermenting and tasting beers using both techniques.

Experimental Setup

After brewing a recent IIPA with an OG of 18.9°P (recipe below) one gallon of wort was split into three half-gallon growlers and fermented using US-05. Two of the beers (U and 2U) were rehydrated in room-temperature wort, and the third (R) in room-temperature water. Based on the results of a methylene blue viability count, the pitching rates were:

• R: Rehydrated, viable pitching rate 0.75 million/mL-°P
• 2U: Unrehydrated, viable pitching rate 0.73 million/mL-°P
• U: Unrehydrated, viable pitching rate 0.34 million/mL-°P

The fermenters were covered with aluminum foil and left at room temperature, which varied from 16-20°C over the course of fermentation. To minimize variations between the fermentations, they were not agitated or aerated.

Results

Once again, I observed a substantial difference in viability, with the yeast rehydrated in water yielding a viability of 72.7%, and the wort-rehydrated yeast 48.8%. Interestingly, this is a higher viability than was seen with yeast rehydrated in lower-gravity wort, though it’s entirely possible that the variation is simply within the error associated with methylene blue testing.

Fermentations in all three beers proceeded similarly, although R began visible fermentation sooner than U or 2U. It did, however take the longest for krausen to fall in R – 11 days, versus 10 days in U and 8 days in 2U. This may be at least partially explained by the lower final gravity of R, as estimated by refractometer readings. U finished at 1.015, 2U at 1.014, and R at 1.013. There may be some inaccuracies introduced by the use of the refractometer formula, but since the OG of each beer was the same, the relationship between the FG values should be correct. Based on a hydrometer reading, the main “control” batch of beer fermented with Wyeast 1272 finished at 1.0145.

A blind tasting revealed that while similar, there were distinct differences between the three samples. All exhibited some degree of “musty” yeast off-aroma, with the smell being strongest in 2U and least prominent in U. 2U also had the highest degree of esters (particularly peach/apricot), and was the only sample to exhibit an acetaldehyde flavor. R was the cleanest overall, with the lowest level of “hot” alcohol character.

Conclusions

A substantial reduction in viability continues to be seen for dry yeast rehydrated in wort. There were also some of the characteristic effects of under-pitching in the wort-rehydrated beers, although the differences were less than in the liquid yeast pitching rate experiment.

These results were also featured on this week’s episode of Basic Brewing Radio.

RAWR! Recipe (PDF)

One ongoing point of contention among brewers is what benefits, if any, result from rehydrating dry yeasts according to manufacturers’ recommendations, as opposed to simply adding the yeast directly to the fermenter. On the technical level, there would appear to be a consensus for a substantial reduction in viability when rehydrating in wort, with most [...]]]> Background

One ongoing point of contention among brewers is what benefits, if any, result from rehydrating dry yeasts according to manufacturers’ recommendations, as opposed to simply adding the yeast directly to the fermenter. On the technical level, there would appear to be a consensus for a substantial reduction in viability when rehydrating in wort, with most sources claiming a reduction on the order of 50%. [1, 2, 3, 4] There exists a substantial body of anecdotal evidence, however, maintaining that rehydration offers no perceptible benefits. I already have some data on the effect of pitching rate on beer flavor, and I think it’s reasonable to infer that a similar reduction in pitching rate would result in similar effects, regardless of whether that yeast was originally a dry or liquid culture. To that end, I decided to do a series of basic viability estimates using dry yeast rehydrated under various conditions.

Experimental Setup

Four cell counts were conducted, using Safale US-05 yeast obtained from a 500 g sachet that had been stored cold and was opened the same day. The yeast, according to the stamp on the packaging, was 176 days old at that point. Assuming that it was initially nearly 100% viable cells, and lost 4% per month, its viability should therefore have been roughly 75-80%. One level one-third teaspoon measure (approx. 1.3 g) was rehydrated in 100 mL of each of four different media: tap water and wort at both typical ale pitching temperature (~18°C) and rehydration temperature (~33°C). The water used is fairly low in mineral content; it was tested the following day at 50 ppm CaCO₃ total alkalinity and 100 ppm CaCO₃ total hardness. The wort used had a gravity of 11.5°P.

After resting loosely covered for half an hour, each sample was capped and shaken to homogenize it. 1.00 mL was then pipetted into 49.0 mL of a 0.02% methylene blue solution and agitated for one minute before a drop was placed on a Neubauer cytometer plate for counting. With the exception of the methylene blue concentration, I use the White Labs protocol for counting – I’ve found a 0.1% solution to be far too dark for effective discrimination of viable and non-viable cells.

Results

With an average total count of 122 cells, the cellular density for the dry yeast works out to 22.9 billion/gram, which correlates well with the established figure of 20 billion/gram considering that the yeast was dispensed by volume rather than mass. The viability estimates for the samples rehydrated in water are also remarkably close to the predicted values, although interestingly enough, the rehydration temperature did not appear to have a substantial effect on viability in either medium. Setting aside temperature as a variable, then, the average viability after rehydrating in wort is 56% of that for the samples rehydrated in water.

Based on these results, I’m confident that the conventional wisdom regarding dry yeast is essentially correct, and that a substantial reduction in the effective pitching rate would result from rehydrating in wort. Additional trials would need to be conducted to determine conclusively whether or not the rehydration temperature is as critical as the manufacturers’ recommendations suggest.

It’s probably fair to state that a majority of breweries operating today are employing single-infusion mashes – that is, they target a single temperature and try to maintain it throughout the entire mash. Broadly speaking, that temperature would almost always be in the range 63-72°C (145-162°F). When a highly fermentable wort is desired, it may [...]]]> Background

It’s probably fair to state that a majority of breweries operating today are employing single-infusion mashes – that is, they target a single temperature and try to maintain it throughout the entire mash. Broadly speaking, that temperature would almost always be in the range 63-72°C (145-162°F). When a highly fermentable wort is desired, it may be necessary to employ a “step mash”, utilizing multiple temperature rests. I don’t want to go into too much detail, but the basic mechanism employed is that the β-amylase enzyme acts first to cleave amylopectin (starch) molecules into maltose (sugar) molecules, and then α-amylase reduces the remaining dextrins (unfermentable sugars), producing the fermentable sugars maltose and glucose. Since the temperature optima for the two enzymes are different, the mash must be heated from the lower-temperature (β-amylase) rest to the higher-temperature (α-amylase) rest. This can be done either by heating the mash directly, by an additional hot liquor infusion, or by decocting a portion of the grist.

The bottom line is that, compared to a single-infusion mash, a step mash requires either additional equipment, additional effort, or both. From a purely practical perspective, it would be preferable to reverse the mash steps and simply allow the mash to cool itself. In order for this to result in a highly fermentable wort, however, the temperature would have to remain in the α-amylase range for a short enough period of time that there is still β-amylase available once the temperature drops. A casual (read: online) survey didn’t turn up any primary sources for the half-life of β-amylase at mash temperatures, so I decided to test the concept myself.

Experimental Setup

Two small test mashes were conducted: one a conventional step mash with β- and α-amylase rests, and the other a “reverse mash” which began in the α-amylase range and was allowed to drop in temperature over the course of the mash. The grists were composed of 500.0 g of Cargill Special Pale malt, and 2.00 kg of strike water, for a mash ratio of 4.00 L/kg (1.92 qt/lb).

In order to ensure that the mashes were of equal length, the reverse mash was conducted first. I had planned on mashing for about an hour total, but the ambient temperature (7°C/44°F) meant that the reverse mash dropped below 60°C after only 35 minutes. The control therefore used two 15 min rests, allowing 5 min for heating. The resulting mash temperatures profiles are shown to the right. After each mash, the grain bag was removed to a second pot containing 1.50 L of water at 85°C (185°F) and agitated continuously for 5 minutes for a combination sparge/mashout. The grain bags were then placed over the pot in a colander and allowed to drain for an additional 5 minutes. In order to eliminate mechanical extraction as a variable, the bags were not moved or touched during this time. The worts were then boiled for 15 min, primarily as a pasteurization mechanism, then set outside to cool.

Once they had chilled below 20°C/68°F, 2.0 L of each wort was decanted into a glass jug, on top of one level teaspoon (approx. 5 g) of dry bread yeast. Assuming a conservative value of 5 billion viable yeast cells per gram of dried yeast (the typical count for a dry brewers’ yeast is 20 billion/gram), this resulted in a pitching rate of at least 1.25 million/mL-°P. The fermenters were then placed side by side in my fermentation closet, with a space heater set for 15°C/59°F. Actual ambient temperatures ranged from 14-19°C (57-66°F). Since I only have one stir plate, the samples were rotated each morning and evening, so that each spent about half its time on the plate. My supposition is that by over-pitching and fermenting warm, the worts both fermented to terminal gravity, even given minor variations in the amount of time they were stirred. After 96 hours, the fermenters were removed and gravity readings taken.

Results

Original gravities for the two samples were 9.7°P for the control and 9.1°P for the reverse mash, corresponding to overall efficiencies of 74% and 69% respectively. On a commercial scale, the increased extraction alone would justify the conventional step mash, although the variation is small enough that it probably wouldn’t be a concern for most home brewers. Final gravities were 1.006 (1.5°P) for the control and 1.007 (1.7°P) for the reverse-mashed sample. The corresponding attenuations are 69% and 67% respectively. While it’s dangerous to make conclusions based on a single trial, it appears that reverse mashing can result in a wort with roughly the same fermentability as a traditional step mash – at least when short rests are employed. More generally, these results suggest that denaturation of β-amylase is not complete after 15 minutes at temperatures favoring α-amylase. Further testing would be needed to establish what limits, if any, exist. I plan to conduct at least one more set of mashes, utilizing longer rests, once summer rolls around.

Update: 15 Oct 2011

This experiment has been extended in a new post.

Winters in Colorado are rough. Aside from the minor annoyances, like not being able to feel my toes for hours at a time, there are major obstacles to be overcome. Where can I brew when my deck has five feet of snow covering it?

So after six years of [...]]]>

Keep any Leonardo DiCaprio jokes to yourself.

Winters in Colorado are rough. Aside from the minor annoyances, like not being able to feel my toes for hours at a time, there are major obstacles to be overcome. Where can I brew when my deck has five feet of snow covering it?

So after six years of living la vida propane, it’s back to an electric stove for me. That isn’t nearly the concern that being unable to use my counterflow chiller is. I was pretty sure that the stove wouldn’t be able to boil 6.5 gallons of wort anyway, so I devised a technique that (I feel) neatly solves both problems.

Among home brewers, partial boils get a bum rap. I suspect that much of the animus is simply pride. We work hard, investing lots of time and money, to transition from extract brewing on a stove to outdoor all-grain setups that rival – and in many cases exceed – the complexity of commercial breweries. There are legitimate concerns associated with a concentrated boil, though:

• Reduced hop utilization, due to the higher specific gravity.
• Greater perceived maltiness due to melanoidin formation from the high (heated) surface-to-volume ratio.
• Increased darkening of the wort, resulting from increased Maillard reaction rates.
• Diacetyl formation from Maillard products.
• Reduced fermentability, again due to Maillard product formation.
• Inclusion of hot/cold break and hop material in the fermenter, since I’m not whirlpooling or chilling in the kettle.

In order to evaluate these effects as best I can, and to get some beer on tap quickly, I chose to brew an American Blonde Ale with an OG of 10°P (1.040 SG). My expectation, however, is that with an average boil gravity of only 16°P, any negatives will be minimized. This also provided an opportunity to experiment with a new hop varietal, Palisade, and my new base malt, Cargill Special Pale. That makes this recipe an educational, albeit infuriatingly named, “SMaSH” beer.

Three days before brewing, I boiled 2.5 gallons of water, which Wolfram|Alpha assured me would result in 5.5 gallons of wort at my target pitching temperature of 17°C (63°F). Aside from needing the ice, this gave me an opportunity to verify that my stove is up to the task of boiling almost four gallons of wort. I was actually surprised by how well it did, heating the water by a nearly constant 2°C per minute, which works out to about 1300 W of power. Allowing for losses, I surmise that the cooktop is designed to nearly max out a 20 A circuit when on “HI”. After a couple hours in a snow bank, the water had cooled to about 50°C, and I split it between three zipper-top plastic bags, which went back in the snow to freeze overnight.

Fast forward to the actual brew day, which was remarkably stress-free. Thanks to Kai Troester’s work, I was able to model the efficiency of the no-sparge mash (projected 71%, actual 70%) very precisely. The rest of the brewing process went normally. Immediately after flameout, rather than my normal whirlpool/chill, I simply cut the bags away from the ice, put the ice in the fermenter, and poured the wort on top. If you wanted to skip yet another step, you could probably pour the hot wort in first and let it stand a few minutes, avoiding having to sanitize the fermenter. Personally, I’m just not wild about the idea of having near-boiling wort in contact with the plastic for any longer than necessary.

After nine minutes, assisted by some gentle stirring, the majority of the ice had melted, and the wort had dropped to 68°F. I aerated for 10 minutes, pitched the rehydrated dry yeast, and left the fermenter in a closet with a space heater set for 64°F. Really, the only wrinkle was that I seriously undershot my pitching temperature target – the wort stabilized at 48°F (9°C). It’s an embarrassing oversight on my part, but apparently the specific heat capacity of wort is much lower than that of water. (In case you’re wondering, c = 3.5 J/g-°C, at least in this case.) But a clean fermentation profile is far from a flaw in this style, and as I can unfortunately attest based on my recent experiences at the brewery, US-05 will happily ferment at these temperatures. As of now, 18 hours after pitching, the fermenter has warmed to 64°F, while still in the lag phase.

Aside from being able to brew instead of, you know, not being able to brew, the most significant benefit I see to using this method is the time savings. From lighting the burner to finishing cleanup, the process took just under three and a half hours. Even allowing for the time needed to make the sanitary ice, using a partial boil reduced the total time investment. I would never advocate sacrificing beer quality in order to save time, but at this point I have to conclude that a brewer interested in transitioning to all-grain brewing not only doesn’t need to move off the stove, he may not want to. The only equipment needed would be a mash tun – which, as Denny Conn will attest, can be a very minimal investment.

Only time will tell if any flaws emerge as a result of using a partial boil in a beer this light. If not, I would have no reservations when it comes to applying the basic technique to other, more aggressively flavored styles. My hope is that, come spring, I’ll be able to brew 10 gallon batches using my existing outdoor equipment.

Sex in a Canoe recipe (PDF)