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Written by Stefan Gagliardi Technical Sales Manager at Brew Culture.
Based on what we are hearing, quick turnaround sour beers, especially the fruited versions, will continue to be popular this summer and will continue to present brewers with slushie-machine-level-brain-freezes due to production schedules and quality program challenges. We’ve already had a few inquiries about ingredient-based solutions for quick turnaround sour beers and it turns out, there are more solutions than ever before. In the article that follows brewers can fnd a list of the diferent approaches they can take, as well as a list of commercial products available through Brew Culture to make quick turnaround sour beers. The key variables explored for each method and product are the costs, risk, and downtime.
Hot Side Souring
Hot side souring consists of inoculating a vessel on the hot side with lactic acid bacteria in a conducive environment to promote a lactic fermentation. The most pop- ular vessel to perform this task is the kettle but with careful consideration this process can also be completed in the mash. Sour mashes present their own unique set of challenges that go beyond the variables covered here. The main beneft of kettle souring is that it limits the lactic acid bacteria to one vessel; wort can be inoculated and then sterilized all within the same vessel. A secondary beneft of kettle sours is the capability of adding hops to the second boil. The alpha acids in hops have antimicrobial properties that can inhibit lactic acid bacteria activity, using this method of souring allows brewers to have more control over the fnal BU and hop favour profle of a beer since the lactic fermentation is completed earlier in the brewing process. The main drawback is that kettle souring can take anywhere between 24 and 48 hours to reach a stable pH or acid level. This can be very inconvenient for breweries that are running their brewhouse at capacity during the summer; more on this at the end of the hot side section with a few ideas on how to make the most of this process.
Brewers now have access to a near infnite number of options that can be tossed into the kettle to produce a lactic fermentation; from milled grain, yogurt, probiotic pills to commercially developed lactic acid bacteria pitches produced by yeast companies. The main beneft of a commercially produced pitch is the promise of a high level of purity. Purity is important for the repeatability of the process and batch to batch aroma and favour consistency. It also eliminates any risk of cross-contamination from using a milkbased product which can lead to labeling issues amongst other things.
In the White Labs catalogue there are three liquid lactobacillus strains to choose from that are suitable for kettle sours:
WLP672 Lactobacillus brevis
WLP677 Lactobacillus delbrueckii
WLP693 Lactobacillus plantarum
WLP672 and WLP693 both produce classic acidic favours profles. The main diference is that WLP672 is heterofermentative meaning it will produce a small quantity of acetic acid, ethanol and carbon dioxide along with lactic acid during fermentation. WLP693 is facultatively heterofermentative meaning it can switch between exclusively producing lactic acid or producing lactic acid along with small quantities of acetic acid, ethanol and carbon dioxide. The outcome of a fermentation with WLP693 depends on the types of sugar available at the start of fermentation. L. delbrueckii is typically classifed as homofermentative, meaning it only produces lactic acid during fermentation; in the case of WLP677 the product is classifed as heterofermentative. WLP677 provides less of a pH drop, producing a softer acidic favour profle more suitable for lighty tart beer styles or fruited sours where the fermentation profle is complimented by the acids imparted by the fruits.
Lallemand has two dry lactic acid bacteria options available:
WildBrew SourPitch™ (Lactoplantibacillus plantarum)
Wildbrew Helveticus™ (Lactobacillus helveticus)
Both these Lallemand products produce a similar fnal pH; however, Wildbrew Helveticus™is reported to produce a higher percentage of lactic acid since it is homofermentative in comparison to WildBrew SourPitch™which is classifed as facultatively heterofermentative.
When comparing all these options it becomes a question of costs, favour preference and production constraints. The benefts of liquid vs dry yeast and bacteria are not a debate I will tackle in this article but here’s what can be said of the subject: The cost for a liquid pitch is approximately twice that of a dry pitch. Liquid pitches are generally less manipulated and fresher than dry pitches. Dry pitches have the beneft of being shelf stable over longer periods of time which provides more fexibility to a production schedule. It’s up to the brewer to determine what is more important to them in making the fnal decision on which product to use.
While we will not go into details about the process variables of kettle sours; here are some parameters that are imperative to producing well-made quick turnaround sours using this process; pre and post inoculation sterilizing boils, incoming wort pH, reduction of exposure to oxygen, fermentation time, fermentation temperature and fnally, a method of determining the end of the process, pH, titration and/or sensory.
If the kettle sour method is the most appealing but the downtime is putting a strain on a breweries production schedule, brewers can explore the following ideas to optimize the process:
Maxing out the kettle volume; anecdotally, on a 20 hL system, I had increased the brew size of my kettle sour to 25 hL. This was done gradually as it was a delicate balance between grain load in the mash mixer, lautering performance and being able to safely boil the liquid in the kettle. If you go down this route, please be very safe regarding the kettle’s capacity as overboils can cause serious injuries.
Take advantage of the fact that pH is logarithmic! In some instances where a mild acidity is required or sour fruits will be added to a beer, brewers can save time by only souring the frst brew of a double batch. Using fruits high in acidity like raspberries, rhubarb and sea buckthorn can allow brewers to achieve a favour profle and acidity level in double batch while only performing the kettle sour step on the frst brew. Careful consideration needs to be taken when designing a recipe like this. Speaking from experience it can free up a production schedule when properly planned. The recipe can also beneft from some of the tools listed in the next point.
There are other tools in a brewer’s tools box like acidified malts and food grade acids. Both can be used to impart 100% of the acids required, as tools to reach a desired level of acidity or to achieve batch-to-batch consistency. It has been said that using these to provide 100% of the acids can lead to a simpler less desirable beer flavour but I can tell you for certain that there are breweries making commercially successful sour beers using this method, especially when fruits are added to the beer. Sometimes brewers just need to put their ethos aside, take the easy road and give the consumers what they want!
Souring In The Fermenter
Breweries that can’t aford to tie up the kettle have started performing the souring process in fermenters. This process involves creating a sterile wort and using a fermenter instead of the kettle as a souring vessel. There are two approaches to lactic fermentations in fermenters. The frst involves performing a lactic fermentation in the fermenter then returning the wort to the kettle for a sterilization step, the second method omits the post lactic fermentation sterilization step.
The gains for method one, returning to the kettle for a post lactic fermentation sterilization step, are that the kettle can be used during the lactic fermentation and a reduced exposure of lactic acid bacteria to cold side and packaging equipment in comparison with method two. It also allows for more liberties with hop favours and bitterness levels since the second boil occurs after the lactic fermentation. The drawbacks are that a fermenter is tied up for the lactic fermentation and extra cleaning steps are required due to equipment exposure to lactic acid bacteria. Special considerations need to be taken during the planning phase of production as well as the cleaning phase to ensure proper hygiene to avoid cross-contamination. For this process all the same products and tips as described in the kettle sour section can be employed.
For breweries in planning or breweries looking to increase capacity in their facility, if quick turnaround sours are a big part of the breweries line up, adding a second kettle or an insulated souring vessel to the brewhouse can be a great way to increase production capacity while keeping the risk relatively low by avoiding lactic fermentations on the cold side.
The last method presented is a co-pitch at the fermenter stage with no return to the kettle. For this method brewers can choose to step-pitch a lactic acid bacteria followed by an alcohol producing yeast, pitch a blend of lactic acid bacteria and alcohol producing yeast or pitch a hybrid yeast product directly into a fermenter. In all the variations of this process, the main drawback is the introduction of a bacteria or yeast on the cold side that can potentially contaminate the rest of the brewery. I recommend having robust cleaning procedures, a cleaning schedule and a method for detecting contaminants across the brewery’s production before embarking on this process. I also recommend considering having dedicated equipment (hoses, gaskets, tanks, etc.) for sour beers. Some breweries go so far as to have a diferent fller to manage this type of process.
If a brewer wants to experiment and design a truly unique recipe, this option presents endless possibilities where they can blend, and co-pitch any lactic acid bacteria with any alcohol producing yeast they can get their hands on. The main beneft of this is ultimate control on favour and fermentation process. In the step-pitch method, brewers can control the timing of each pitch; typically, brewers will give the lactic acid bacteria a head start by pitching it upon transfer and opting to pitch the alcohol producing yeast around the 48-hour mark. The drawbacks are that this can get expensive, managing fermentation temperatures and batch-tobatch inconsistency due to the nature of a co-pitch when dealing with collecting and repitching.
For more consistent results, White Labs has developed two blends allowing brewers to start with a commercially produced copitch that has a standardized level of both lactic acid bacteria and alcohol producing yeast. The main beneft is the batch-tobatch consistency and cost savings as the blends cost the same as a single lactic acid pitch. The main drawback is these blends tend to be single use since collection and repitching is very difcult to manage.
WLP630 Berliner Weisse Blend –A blend of a German Weizen yeast and Lactobacillus bacteria
WLP631 Appalachian Tart – A blend of Kveik yeast and Lactobacillus sp.
While the Berliner Weisse Blend is said to take up to several months to develop its tart character, complete fermentation can be achieved in 72 hours with Appalachian Tart under the right conditions.
Finally one of the most innovative products on the market for making quick turnaround sour beers in a fermenter is Lallemand’s WildBrew Philly Sour™. Philly Sour™ is a unique species of Lachancea that produces moderate amounts of lactic acid in addition to ethanol in one simple fermentation step. Levels of lactic acid production can be controlled by increasing or decreasing the level of available glucose; a higher amount of available glucose provides more acidity to the fnished product. The main beneft is the simplicity of the product as it eliminates the kettle sour step and associated downtime without introducing lactic acid bacteria to the brewery. Lallemand has done some extensive testing to demonstrate the lower risk level of this species compared to lactic acid bacteria. Philly Sour™ is sensitive to normal CIP procedures and is a slow grower leading to being outcompeted by traditional brewing strains. The price is similar to a liquid co-pitch with the added beneft of an extended shelf-life which can give brewers more fexibility on their brewing schedule. Despite risk level claims, the main drawback is brewers still need to show some level of quality control to avoid contamination.
Each of the options presented has benefts and drawbacks to producing worldclass quick turnaround sour beers. As with all things related to brewing, it becomes a question of what is more valuable to brewers. Hot side downtime, labour, cleaning chemicals, quality programs and ingredients all have associated costs; the brewers task is to fnd the right compromise amongst these without compromising on beer quality.
For supplemental information on products or processes described in this article do not hesitate to reach out to the Brew Cultures Technical Team by writing to: info@brewculture.com.
