Update: We've got a recipe made specifically with this yeast in mind: It's Always Sour in Philadelphia! Check it out (and be sure to read the rest of this post for some advice on brewing with Philly Sour).
The enduring popularity of kettle sours (or dessert sours when lactose is added) is not a turn of events we at Bitter & Esters would have foreseen 10 years ago when we opened our shop. Beer styles like Gose or Berliner Weisse were considered a wee bit esoteric. Most homebrewers didn’t want to intentionally add lactobacillus to their beer for fear of cross contamination.
Because we live in a confusing, turbulent, and occasionally awesome time, homebrewers have access to tools and yeasts that simply didn’t exist until very recently. You may have heard about the new strain of yeast from our friends at Lallemand called Philly Sour (maybe from us!). If you haven’t, here’s the skinny: it’s a yeast strain that creates lactic acid as well as alcohol. This means you can make a sour beer without having to deal with any of those pesky Lactobacillus bacteria infecting your equipment.
Before Philly Sour (henceforth “BPS”) there were two ways to make sour beer. One is called Kettle souring, where you would take unhopped wort (because hops make lactic acid bacteria less likely to work their souring magic), boil it, cool it down to around 90-110˚F (32-43˚C), add Lactobacillus bacteria and keep it warm for 24 to 48 hours while the bacteria soured your wort to your preferred pH (i.e. level of sourness). Then you’d boil the wort to kill the bacteria, add hops according to recipe, cool down and pitch yeast like any other beer. This was always the fastest method to make sour beer.
The other method is the traditional method of adding your yeast and Lactobacillus into a lightly hopped (or un-hopped) wort in your fermenter and wait, sometimes up to a year. Of course this is a simplified description of traditional souring methods, but you get the gist.
Both of the above options work, with the former being more effective than the latter (especially given the Lactobacillus varieties now available), but now we have a third alternative in Philly Sour. It is derived from a recently discovered species of wild yeast isolated off of a dogwood tree in The Woodlands park graveyard by the University of the Sciences in Philadelphia. Philly is not a Saccharomyces yeast but a novel Lachancea yeast species. Turns out there have been other strains of yeast in the wild that both ferment for alcohol and lactic acid, but this strain happens to taste good!
Expect flavors of red apple and stone fruit, especially peach. And the coolest thing is that you just need to make a wort and pitch it like any other yeast strain. No keeping your wort warm for two days while it sours, no waiting months if doing the traditional method, and no need to worry about hop additions preventing the bacteria from creating lactic acid.
(Side note: sour and bitter flavors aren’t known to taste great together so some restraint is encouraged before making too bitter of a wort. A sour West Coast IPA doesn’t sound like our cup of tea, but we won’t stop you.)
Looking for a recipe to try?
Any of these recipes will work as a kettle sour - just skip the lactobacillus addition and try the Philly Sour instead. Even our stalwart Resistor Pale Ale can be done as a Kettle Sour if you're feeling adventurous.
Want to get the most out of Philly Sour? We’ve got a few tips for you. First, it’s a medium-high attenuator (70-85%) depending on the fermentability of your wort, so plan accordingly. Second, it’s a strong flocculator so you’re going to get clear beers - not hazies. Rehydrating never hurts and makes it easier to pitch into your wort.
Pitch rate, fermentation temperature, and wort composition are big factors in how much acid this yeast will produce. Pitch 1g per liter for worts at 1.050 OG (original gravity) or lower, meaning one package is sufficient for five gallons. If you’re going over 1.050 OG, 2 packages are recommended. Repitching Philly Sour is not recommended because of the stress the acid puts on the yeast.
This yeast likes it hot. Fermenting between 71-80˚F (22-27˚C) will ensure proper acid production and attenuation. After pitching, the yeast will get to work souring the wort for the first 5 days and then alcohol production takes over. Because the yeast consumes glucose to create lactic acid, your target abv will be lower. Depending on wort composition, the yeast can consume 5 to 15% of the OG during the acidifying stage. Terminal gravity is usually reached in 10 days with the final pH being around 3.2-3.5. When we’re talking about pH the difference between 3.2 and 3.5 can be relatively large - if you’re looking for something bracingly sour, consider using the Omega Lactobacillus blend in lieu of Philly Sour for a little more control over acidity levels.
Speaking of wort composition, more glucose means more acid. Mashing cooler at a beta amylase rest (around 148˚F) will help create a more fermentable wort which will make a more sour beer. You can also add dextrose or sucrose during the boil.
Adding fruit during fermentation will also affect sourness and flavor. Adding fruit during the first five days will lower pH, adding after that will increase fruit flavor and alcohol.
Since Philly Sour is a yeast and not Lactobacillus, you can add lactose to your wort for some sweetness to balance the acid and the yeast will not consume it, unlike Lactobacillus (which literally has Lacto in its name).
Additionally, contamination risk is low with Philly Sour because . . . it is not a bacteria and it is easily outperformed by other yeasts. Your equipment should be fine with your normal cleaning and sanitizing regime. But if you are at all nervous, just keep a separate fermenter for sour brews.
Other Styles (Farmhouse / Meads / Ciders)
Are you looking for a Farmhouse-style with yeast character and a little bit of sour? Just don’t pitch your second strain of yeast at the same time as Philly Sour. The second strain will dominate and you will get no acid production. Wait that five days (or until you reach your desired pH) while Philly does it’s thing and then pitch your second strain. Consider using a dry yeast so you don’t have to worry about the vitality of the yeast as dry yeasts are packaged at the peak of health.
There have been some promising results making sour meads and ciders using Philly Sour, but just as you would with a regular mead or cider, make sure to use plenty of yeast nutrient.
There you have it! This is a very new strain and we’ll see what the future holds. As always the only way to really know is to make some beer!