Many home brewers who are unfamiliar with all-grain brewing often ask if we can shorten their brew day by reducing the boiling time for the wort. Their reasoning is usually along the lines of, “If the purpose of boiling is to sterilize the wort, can I boil it for just long enough to achieve sterilization and save time?”
While it is possible to slightly reduce the boiling time (less than 60 minutes), it is important to note that boiling the wort serves a more critical function in beer brewing than sterilization alone (though sterilization is indeed important).
Wort boiling is an incredibly vital step in the brewing process. It holds more importance than many brewers realize, including the following:
Halting Enzyme Activity
This largely depends on the temperature range at which enzymes are active. However, most enzymes denature (lose their function) between 50-75°C. That’s why we have a mashing step during the brewing process. Once the wort reaches its boiling point, enzymatic activity is typically no longer a concern. This is crucial because enzymes affect the fermentability of the wort, ultimately impacting the final beer. We recommend incorporating a mash-out step by heating the wort to 75°C at the end of mashing and maintaining that temperature for 10 minutes.
Concentrating the Wort
When the wort is boiled, water evaporates (visible as steam). The more water evaporates, the more concentrated the wort becomes, resulting in a higher original gravity (OG) to some extent. That’s why it’s important to consider evaporation rate when calculating OG. As a reference point, the evaporation rate should be around 2.5 liters per hour.
The calculation is as follows:
Volume before boiling x Gravity before boiling = Volume after boiling x Gravity after boiling
You can calculate the volume after boiling by subtracting the evaporation rate from the volume before boiling. For example, if your pre-boil volume is 28 liters and you boil for 1 hour, then the volume after boiling would be 28 – 2.5 = 25.5 liters.
Now you can substitute 25.5 into the equation. In this example, let’s assume a pre-boil gravity of 1.050 and a pre-boil volume of 28 liters.
28 x 50 = 25.5 x Gravity after boiling
(28 x 50) / 25.5 = Gravity after boiling
1400 / 25.5 = Gravity after boiling
54.9 = Gravity after boiling
So, your gravity after boiling would be approximately 1.055. This means that if you calculate early enough, you can make adjustments such as adding more water or boiling for a longer period.
Isomerized Alpha Acids
Alpha acids are a factor considered by brewers when calculating the bitterness of beer. However, they are actually insoluble in wort. Only through boiling do they convert into more soluble iso-alpha acids. Studies have shown that isomerization of iso-alpha acids rapidly occurs at boiling temperatures. Within the first 30 minutes of boiling, over 90% of the wort’s bitterness will develop. If your main concern is achieving the desired bitterness, you can assume a 10% loss of utilization and boil for just 30 minutes (although the gravity will decrease after boiling). Maximum isomerization typically occurs within 60-70 minutes of boiling, and extending the boiling time can further increase utilization.
Boiling the wort triggers three reactions that contribute to color development. The first is the Maillard reaction, which occurs between carbonyl groups and amino acids and is responsible for browning in food. Secondly, sugar caramelization takes place, leading to color changes. Lastly, some polyphenols undergo oxidation, adding to the overall color of the wort.
When you boil the wort, the calcium compounds present react to form insoluble compounds. As a result, at least half of the calcium in the wort separates from the liquid by the end of boiling. This separation is primarily influenced by the wort’s pH during boiling. To promote enzyme activity, it is recommended to aim for a mash pH of 5.2-5.5. Ideally, your pre-boil pH should be around 5.2-5.4 because lower values negatively impact hop utilization, while higher values increase perceived bitterness. Boiling the wort lowers the pH by 0.1-0.2 units, bringing the pH of the fermenting wort to around 5.0-5.3. Fermentation further reduces the pH, with the final beer typically falling within the range of 4.2-4.6.
Ensuring the desired pH drop during boiling is essential as it enhances clarity, improves beer flavor, encourages yeast growth, and inhibits bacterial growth.
Removal of Volatile Compounds
Boiling the wort allows for the removal of unwanted volatile compounds, such as dimethyl sulfide (DMS), through steam evaporation. DMS is undesirable in beer as it imparts a “sweet corn” taste. By controlling the duration and intensity of boiling, the level of DMS can be managed.
These are just a few of the reasons why wort boiling is a crucial part of the brewing process and deserves more attention than it sometimes receives! Have you ever experimented with reducing or extending the boiling time? What were the results?
Copper Beer Brewing Equipment
If you have any insights or questions regarding our beer brewing equipment, feel free to contact us. You can reach Kate via email at firstname.lastname@example.org.