Kettle souring is a technique that allows amateur brewers to consistently produce batches and batches of drink with the perfect level of sourness. Unlike traditional beer souring methods, which take months or even years, this process takes just 24 hours to complete. Add a strain of pure lactobacillus to the classic wort and allow the bacteria time to break down the sugars into liquid. When the mixture reaches the pH you want, you get a light, full-bodied and tart beer just enough to give a feeling of freshness.
Steps
Part 1 of 3: Prepare the Must
Step 1. Fill the kettle with water
Use the freshly purified one, make sure it is perfectly clean, transparent and odorless; as a general rule, you need 1.5 liters of water for every 500g of malt.
- The pH and mineral content of the water affect the flavor of the final product, so try to get a good quality and neutral one.
- You can contact the municipal offices to have the water quality analyzes of your municipality.
Step 2. Heat it to 74 ° C
Turn on the burner under the kettle and start increasing the temperature of the liquid; if the kettle does not have a direct heat source, boil the water before transferring it to the container and allow it to cool to the appropriate level.
- The specific type of malt extract you are using to make the wort melts better at higher temperatures.
- The must is the liquid left over from the mash and contains the sugars necessary to start the acidification process.
Step 3. Add the malt extract
Slowly mix the powdered product taking care to break up any large, paste-like lumps as soon as it forms on the surface. Keep stirring until the malt is completely dissolved and evenly distributed in the water.
- Most home brewing kits also include the extract among other ingredients.
- This is the simplest product to prepare the must to be soured. As your brewing skills improve, you can also start experimenting with other methods by grinding your own custom grain blend.
Step 4. Let the mixture sit for an hour
Meanwhile, the malt extract begins to release natural sugars; stir occasionally, but remember to keep the kettle covered.
- To find out if the wort has had plenty of time to absorb the sugars from the malt, run the iodine test. Cool a sample of about 30 ml and add a couple of drops of iodine; if the liquid turns dark purple, the wort is not ready. If it does not change color, it means that most of the starches have been dissolved.
- If you prefer a stronger beer, wait another 15-30 minutes.
Step 5. Keep the wort at a constant temperature
After extracting the malt, the water temperature should remain between 64 and 68 ° C; if it reduces excessively, light the burner for a few moments or add a small dose of boiling water until the correct level of heat is restored.
- Make sure that the temperature does not drop below 30 ° C, otherwise you will get a watery wort with little flavor.
- Keep the kettle insulated by using burlap, blankets or similar fabrics.
Part 2 of 3: Adding the Bacterial Cultures
Step 1. Boil the wort for at least 5 minutes
A quick pre-boil sterilizes the wort by killing harmful bacteria, enzymes and other unwanted substances. If you ignore this step, these microorganisms release by-products that can interfere with the final taste of the beer or even cause stomach problems.
- The first boil can take up to 10-15 minutes, depending on the amount of beer you are brewing.
- Remember to sterilize any utensils that need to come into contact with the wort.
Step 2. Wait for the temperature to drop to about 37 ° C
Turn off the burner or partially open the kettle lid to let the heat escape. Lactobacilli prefer a warm environment, so remember to reduce the temperature of the liquid to a "hospitable" level before adding the bacteria.
The temperature need not be exactly 37 ° C; these crops also live in environments at 30 ° C; however, a lower heat level extends the time of kettle souring
Step 3. Bring the wort pH to 4.5
Add a few drops of food-grade lactic or phosphoric acid and mix. Use a pH meter to measure the acidity level; starting with an acid wort you create the best possible fermentation conditions and promote faster bacterial action.
- By balancing the pH of the solution, you prevent other bacterial strains from taking over and turning the beer into an unpleasant or dangerous drink; in addition, this also protects the yeast proteins, which means that the beer will have a richer flavor and more body.
- Use a dropper to have more control over the dose of acid and avoid spilling too much at one time.
Step 4. Introduce the lactobacilli into the wort
Simply throw the bacteria into the kettle, mix thoroughly and cover the container again. To properly sour beer, you need to use around 10 million bacterial cells for every milliliter of wort. Read carefully the dosage instructions on the package to know how much product to use based on the amount of beer you are brewing.
- Most brewers recommend using a pure culture that allows for consistent and predictable results.
- Pure cultures of bacteria such as lactobacilli are typically sold in vials at home brewing supply stores; if you can't find them, you can find good substitutes among food supplements.
Part 3 of 3: Sour the Beer
Step 1. Wait for the process to begin
In most cases it takes 24-48 hours; obviously, the amount of beer you are producing plays a major role in the acidification times. Return to the kettle to monitor the process every 8-12 hours.
While the must rests, the lactobacilli "celebrate" with the sugars present in the liquid, releasing lactic acid and waste products; it is precisely the lactic acid that gives the beer its characteristic notes
Step 2. Check the pH of the wort
The best way to do this is to use an accurate pH meter. The desired acidity level is around 3, 6 or just higher to get the slightly tart flavor of Berliner Weisse, Gose and most Saisons. When the pH is close to 3.3, a drink is obtained whose aroma is similar to that of new Lambics and traditional sour beers.
- The lower the pH, the higher the acidity level (and consequently the harshness) of the beer.
- If you don't have a pH meter, you can check the sourness of the liquid in the traditional way by tasting it; however, remember that the tool must be sterilized.
Step 3. Boil the wort for 60-90 minutes
Once the desired pH is reached, you can cook it as usual. The second longer boil is needed to stabilize the remaining bacteria, infuse a softer flavor and more body; at this point, safely add the hops you prefer and the other additives.
To get a beer with a distinctive flavor, try using different combinations of fresh fruit or aromatic spices
Step 4. Add yeast to complete fermentation
Cool the water around the kettle to lower the temperature, add the correct amount of yeast based on that of the wort and mix; then, transfer everything to the fermentation vessel, seal it and wait for the process to begin.
Keep experimenting until you find the perfect balance between flavor and acidity; Brewing is like chemistry, it requires a lot of trial and error
Step 5. Let the wort ferment for 1-2 weeks
Within a few days, you will have a batch of delicious home brew with the ideal level of acidity. In the meantime, remember to keep it in a dark and cool place; the cellar and garage are perfect for letting it rest while fermentation comes to an end.
- Use your beer enthusiast sensibility to decide when a particular batch has had plenty of time to ferment; the longer you wait, the more decisive and pungent the aromas are.
- The kettle souring method is ideal for brewers who love the highly acidic notes of the drink, but don't want to wait months and months for the crops found in raw grains to do their job.
Advice
- Always use properly sanitized equipment; even the slightest trace of bacteria can ruin an entire batch of beer.
- Estimates and evaluations "by eye" usually lead to an undrinkable product. Rely on essential tools such as a thermometer, a pH meter, a hydrometer and take precise measurements at every stage of production.
- Eliminating oxygen from the wort and CO infusion2 you can prevent organisms in the air from contaminating beer.
- If you can't get a pure lactobacillus culture, you can try making wort with yogurt. It might seem strange, but natural one contains the same bacteria as ground cereals and can be a good solution if you don't have anything else.
- Kettle souring is a technique that is influenced by many factors; it may take dozens of tries before you can develop some mastery.
