Collaborative Fermentations
With collaborative beers so popular in craft brewing, why aren’t there more collaborative fermentations? For thousands of years all beer fermentations were mixed-fermentations. That changed when brewing scientists (most notably Pasteur and Hansen) discovered the true identity of the tan goop left at the bottom of the fermenter and developed pure culturing techniques. Cultures grown from a single-cell ferment more reliably and exhibit cleaner more consistent flavor profiles. Today, costing only a few dollars, brewing yeast cultures are available from more than a dozen labs. Why then would any homebrewer want to mix together brewer’s yeast strains?
Improving Fermentation Dynamics
The most common reason to blend two or more yeast strains is to increase attenuation when using a strain with a desired flavor profile but lackluster logistics. For example, the classic Belgian saison strain is known for sloth towards the end of fermentation. By combining it with a small amount of a more aggressive and attenuative strain you can achieve that classic saison flavor without the wait! This is our approach at Modern Times Beer (in San Diego, California) for our year-round saison, Lomaland. The Saison Dupont strain (e.g., WY3724, WLP565) won our taste trials but took too long to make economic-sense in a commercial setting. After our test blend with French saison (e.g., WY3711) and American ale (e.g., WY1056, WLP001) provided lackluster results, we happened to read Nathan Watkins’ “Multiple Personalities: Successfully Blending Yeast Strains” (Zymurgy May/June 2013) which suggested pairing it with Westmalle’s Trappist ale strain (e.g., WY3787, WLP530). The 95% Dupont, 5% Westmalle blend that we now pitch produces a beautifully peppery aroma from a fermentation that lasts just a few days.
The same basic technique with a different ratio can be applied to soften the varietal character of certain yeasts. Hefeweizens are off-putting to some drinkers due to their intense banana (isoamyl acetate) and clove (4-vinylguaiacol) aromatics. While altering the fermentation temperature can reduce ester (banana) production, this approach often causes the phenols (clove) to stand out even more. To soften both aromatics, try fermenting with a blend of hefeweizen and American, English, or Kölsch yeast. I would suggest starting with at least 40% of the neutral strain, but it may still take multiple iterations to dial in the respective pitching rates to achieve the desired balance.
Another practical reason to pitch more than one yeast strain is to increase alcohol tolerance. Many yeasts start to falter once they produce 10–12% ABV. If you are attempting to brew a souped-up barleywine or imperial stout, a highly tolerant strain can be pitched once attenuation slows. White Labs WLP099 (Super High Gravity Ale Yeast) is a great choice, Champagne and other wine strains not so much. Strains that evolved to ferment fruit juice can withstand high concentrations of alcohol, but are usually ill-equipped enzymatically to ferment the more complex sugars (e.g., maltotriose) remaining in a partially-fermented beer. The exception is when bottle conditioning, due to the simpler glucose and sucrose priming sugars.
Wine Yeast for Flavor
Wine yeasts can actually produce some fantastic flavors in a beer if pitched early in the fermentations and then an ale or lager yeast can be added later to complete attenuation. Be careful to select a wine strain that does not produce a toxin deadly to brewer’s yeast. Lalvin 71B-1122 (Narbonne White Wine Yeast), is a particularly popular choice. Front Street Brewery’s (Wilmington, North Carolina) Mosaic Saison has proven wonderfully fruity and saison-like fermented with this strain. Rather than pitch brewer’s yeast, Front Street added enzymes to increase the wort’s fermentability.
I pitched a red wine yeast, Lallemand BM45 (Brunello), for primary fermentation of a Flemish red with wonderfully cherry-plummy results. However, I made the mistake of pitching a souring blend that contained brewer’s yeast at the same time as this killer wine strain (i.e., one that produces a competitive factor). The result was sulfury for more than a year before the Brettanomyces eventually cleaned up (luckily Brett is not susceptible to these toxins). Lalvin Bourgorouge RC212 is a good option for a non-killer red wine strain.
Things to Consider
No matter your goal, select strains that perform well under similar conditions if they are to be pitched together. For example, a mixture of a saison strain that excels at temperatures in the 70s and 80s °F (21–32 °C) with a lager yeast that performs best around 50 °F (10 °C) would likely result in a less than ideal beer. Either the saison yeast will stall at the temperature the lager yeast prefers, or the lager yeast will produce harsh flavors if the fermentation is warm enough for the saison.
Once you have selected your yeast strains, propagate them separately. Attempting to grow a mixed culture will lead to a population shift. You can estimate the relative density of the cultures by allowing them to settle out after growth is complete. Start with a 50-50 blend if you want roughly equal activity, or something more lopsided if you want the flavor of one strain to be more expressive. If you can’t be bothered or don’t have the time, just pitch directly from the package by volume. Use a yeast calculator to estimate the viability of each culture based on the manufacturing date. You can also use the calculator to determine the ideal total pitching rate and ensure you introduce enough cells. If this seems like more effort and expense than you are willing to devote to dialing in a blended culture, many yeast labs sell pre-mixed liquid cultures for the same price as their pure cultures.
A common issue for commercial breweries that repitch mixed cultures is that populations shift from batch-to-batch. One strain may reproduce more rapidly than the other, or flocculate more rapidly, making that strain more likely to be harvested and repitched. This is less of an issue for home-brewers who tend to buy fresh yeast more often. In one test, White Labs found that a 50-50 blend (WLP001 and a customer’s malty house ale strain) had drifted to 85-15 after just four batches, although the brewery was still happy with the results (“A Guide to Blending Yeast Strains NHC 2014” by Kara Taylor). At Modern Times Beer, we usually purchase a fresh pitch of saison blend for every five batches of Lomaland. To get the most out of a pitch, a brewery might consider pitching the blend into a different beer towards the end of the yeast’s usability, a beer expected to complement the drifting yeast character.
It can be especially fun to produce a series of connected beers by repitching a yeast blend. I’m in the middle of a series of saisons brewed with hops and other ingredients from given regions. For example, Motueka and Nelson Sauvin hops and a bottle of Sauvignon Blanc all from New Zealand (talk about citrusy terroir!). When each batch is complete I harvest the yeast slurry for the next batch. If the blend seems lacking in a particular attribute I’ll pitch the slurry along with an additional strain into the next batch. My blend includes several Brettanomyces strains and now Lactobacillus in addition to The Yeast Bay’s Saison Blend.
If you are using a blend with only Saccharomyces, sanitation has to be a priority because a lapse in any of the brews will doom all future batches brewed with the blend.
Hybrid Strains
While population shifts are an inevitable part of repitching blended cultures, there is an alternative that can combine the best attributes of two strains with the reliability of a pure culture. Saccharomyces usually produce asexually by budding offspring that have only subtle genetic differences. Under the right conditions though, two cells can mate to create hybrid daughter cells. Those descendants exhibit a blend of genotype and sometimes phenotype (observable traits) from the two parents.
Omega Yeast in Chicago was the first lab to release a hybrid brewer’s yeast, Saisonstein’s Monster OYL-500. The hybrid was created by stimulating the parent cells (a classic Belgian saison and a highly attenuative French saison) to form spores. These spores each have a single set of chromosomes (haploid) allowing them to combine to form a cell with a full set (diploid). Eight of the resulting hybrids were propagated and then evaluated in split fermentations with the best strains advancing to larger trials. The eventual winner displays much of the peppery flavor profile of a classic saison, but with more fruit and attenuation speed similar to the French saison.
While there are now hundreds of brewing yeast isolates available, it is still worth exploring the potential that blended cultures hold. Whether your goal is to increase attenuation, raise alcohol tolerance, or produce a unique flavor profile, a mixture of strains may be the answer. It can be delicious and inspiring to collaborate on a batch with another homebrewer, each of you bringing talents, techniques, and sharing the work. Do the same for your yeast, get them a friend.
Recipe
Nu Zuland Saison
(5 gallons/19 L, all-grain)
OG = 1.062 FG = 1.007
IBU = 38 SRM = 3 ABV = 7.25% pre-wine (7.4-7.6% post-wine)
*One of the two Brettanomyces strains I used in this beer was obtained from homebrewer Jason Rodriguez, who isolated it from a bottle of Brasserie Cantillon. Jason termed the strain CB2. Read about it at:
http://www.themadfermentationist.com/2012/08/bottle-conditioning-with-brett-belgian.html. It has some similarities to the strains listed in the recipe.
Ingredients
8.3 lbs. (3.76 kg) Pilsner malt
4.2 lbs. (1.91 kg) wheat malt
11 AAU Rakau hop pellets (30 min.) (1 oz./28 g of 11% alpha acid)
14 AAU Motueka hop pellets (0 min.) (2 oz./56 g of 7% alpha acid)
24 AAU Nelson Sauvin hop pellets (0 min.) (2 oz./56 g of 12% alpha acid)
2 oz. (56 g) Motueka hop pellets (dry hop)
2 oz. (56 g) Nelson Sauvin hop pellets (dry hop)
½ tsp. yeast nutrient (15 min.)
½ Whirlfloc tablet (5 min.)
The Yeast Bay Saison Blend yeast
White Labs WLP644 (Brettanomyces bruxellensis trois) yeast
Wyeast 5112 (Brettanomyces bruxellensis) or White Labs WLP650 (Brettanomyces bruxellensis) yeast *
Wyeast 5223-PC (Lactobacillus brevis) or White Labs WLP672 (Lactobacillus brevis) bacteria
0.75-1.5 L Sauvignon Blanc white wine from New Zealand
1 cup corn sugar (if priming)
Step by Step
Heat 15 qts. (14 L) of water to achieve a mash temperature of 148 °F (67 °C). Hold at this temperature for 60 minutes or until conversion is complete. Sparge slowly with 170 °F (77 °C) water, collecting wort until the pre-boil kettle volume is around 6.5 gallons (24.6 L).
Boil the wort for 75 minutes adding the first hop addition with 30 minutes left in the boil and the second hops addition as you turn off the heat. Give the wort a long whirlpool stir and let settle for 30 minutes prior to chilling. After 30 minutes, chill the wort to 65 °F (18 °C), let the break material settle, rack to the fermenter, aerate the wort with filtered air or pure O2, and pitch all yeast and bacteria. Ferment at 75 °F (24 °C). Once the gravity is stable, add the dry hops. After two weeks add the wine to taste in the bottling bucket. Bottle or keg each aiming for 2.9 volumes of CO2. Use the priming chart at https://byo.com/resources/carbonation to determine your priming sugar needs. I prefer keg conditioning for hoppy beers with Brettanomyces because it allows me to serve them younger. The pressure of
the secondary fermentation also seems to increase the speed with which the Brettanomyces produces its signature character.
Nu Zuland Saison
(5 gallons/19 L, extract only)
OG = 1.062 FG = 1.007
IBU = 38 SRM = 5 ABV = 7.25% pre-wine (7.4-7.6% post-wine)
Ingredients
4 lbs. (1.8 kg) Pilsen dried malt extract
2.9 lbs. (1.32 kg) wheat dried malt extract
11 AAU Rakau hop pellets (30 min.) (1 oz./28 g of 11% alpha acid)
14 AAU Motueka hop pellets (0 min.) (2 oz./56 g of 7% alpha acid)
24 AAU Nelson Sauvin hop pellets (0 min.) (2 oz./56 g of 12% alpha acid)
2 oz. (56 g) Motueka hop pellets (dry hop)
2 oz. (56 g) Nelson Sauvin hop pellets (dry hop)
½ tsp. yeast nutrient (15 min.)
½ Whirlfloc tablet (5 min.)
The Yeast Bay Saison Blend yeast
White Labs WLP644 (Brettanomyces bruxellensis trois) yeast
Wyeast 5112 (Brettanomyces bruxellensis) or White Labs WLP650 (Brettanomyces bruxellensis) yeast *
Wyeast 5223-PC (Lactobacillus brevis) or White Labs WLP672 (Lactobacillus brevis) bacteria
0.75-1.5 L Sauvignon Blanc white wine from New Zealand
1 cup corn sugar (if priming)
Step by Step
Heat 5 gallons (21 L) in your brewpot. When the water starts to boil, remove from heat and add in all the DME. Stir until all the extract is dissolved then return the pot to heat and return to a boil. Boil the wort for 30 minutes adding the first hop addition once the boil is achieved and the second hops addition as you turn off the heat. Give the wort a long whirlpool stir and let settle for 30 minutes prior to chilling. Follow the remainder of the all-grain recipe.
