Boiling

Why to boil the wort?

The boil is a mandatory step in the production of homemade beer. Besides the sterelization, calcium compounds react to form insoluble compounds meaning by the end of the boil, at least half of the calcium that was present in the wort has been separated from the liquid and this is largely responsible for the decrease in wort pH during the boil. Additionally it will activate flavor from hops and spices.

Objectives of boling

• Sterilization of the wort

We always joke that before the boil everything that falls into the vessel becomes seasoning! In fact, we can say that because the risks of the dreaded contamination occurring before boiling are practically nonexistent, since by boiling the wort we are sanitizing it!

Although the wort separation and sparging processes are normally conducted at elevated temperatures (76-80°C), wort entering the kettle contains numerous microorganisms-yeast, molds, and bacteria-which can result in off-flavors and numerous other problems.

• Enzyme Inactivation

It is done during the optional Mash out phase. Boiling fixes the carbohydrate composition of the wort by inactivating residual enzymes that are responsible for carbohydrate and protein degradation and that may have survived mash-off or sparging.

• Concentration of the wort

The wort must be concentrated by evaporation since the water used in mashing and sparging has produced wort lower in specific gravity than the target gravity. During the boil there is a great evaporation of water and therefore the initial density (OG) of the wort goes up a lot. This increase, obviously, varies from how long you decided to let it boil as well as the intensity of that boil. Normally the wort should be boiled from 60 to 90 minutes, depends on the type of beer. It will increase the OG (original gravity) if we compare with the wort before the boil. It happens because we have less water with the same content of fermentable sugars.

So it is an interesting strategy to measure the wort gravity before boiling so we can predict the OG to be obtained and correct it by increasing or decreasing the time or intensity of the boil or even continuing the washing process. Each equipament will give a specific ratio as it depends on the power of the heating and some other variants, like diameter of the vessel, etc.

• Evaporation of unwanted substances

During boiling, certain substances that can cause bad flavors and aromas in your beer, like the famous DMS, are eliminated with evaporation. That is the main reason we should never cover the vessel during boiling the wort. Another reason to avoid covering the vessel is the Boil-Over.

DMS (Dimethyl sulfide) is a sulfur compound that is typically considered an off-flavor in beer at high concentrations and is introduced into beer from the thermal decomposition (wort heating) of S-methylmethionine (SMM) produced in the embryo of barley during germination. That corresponds to the aroma of green corn or other vegetables.

• “Activation” of hops and spices

In addition to all the aforementioned advantages, during the boil there is also the isomerization of the hops alpha-acids which in turn serve to confer the famous bitterness of the beer. Also, many spices like coriander, orange peel, etc. are added at the end of the boil and it serves to increase the extraction of aroma and taste of these spices!

Isomerization is the result of the effect of heat on the alpha acids. The process is both time and temperature dependent. Iso-alpha acids are formed typically during wort boiling, when hops are added and alpha acids are extracted from the hops' lupulin glands (or from the hop resin in hop extracts).

The major flavor contribution of hops in beer is bitterness from iso-alpha acids. During the boil, the insoluble alpha acid extracted from hops is converted to a more soluble iso-alpha acid.

• Production of Melanoidins (Maillard reaction)

The production of melanoidins (the Maillard reaction) occurs when reducing sugars from carbohydrates react with amino acids that are derived from the proteins during mashing. Caramelization is a chemical process that affects sugars subjected to temperatures of 200°C or greater.

• Improove the shelf life of the beer

• Deepening of wort color

During boiling, the color of the wort becomes darker. This is brought about by the formation of pigments (melanoidins), the oxidation of polyphenols, and the caramelization of sugars.

• Protein Precipitation (trub formation)

During the boiling process, it is necessary to decrease the level of high molecular weight nitrogen found in the malt. Protein precipitation occurs as the wort loses its turbidity during boiling, and material breaks out of suspension and precipitates as proteins coagulate. With coagulation of proteins (Hot Break) that join and decant to the bottom of the pan together with the remains of the hops used.

• Oxidation of Polyphenols

The oxidation of polyphenols is another source of color formation. Polyphenols are sometimes referred to as "tannins" and may be derived from malt husks and hops.

• Reduction in Wort pH (usually to a level close to 5,2)

The pH of the wort starts to decrease during mashing and continues to fall during wort boiling to reach a final pH of between 5.2 and 5.3.

Boiling

Here is a step by step with details to optimize the boil.

1 - During the lautering (previous process before boiling) add enough water to have around 10% to 15% more wort than you planned as a final “batch size”. This is because a considerable amount of water evaporates during the boil (the precise value depends on the equipament and boil time) which ends up reducing the total amount of beer even if it increases its density. For example, in 45 liters batch of wort with a gravity of 1061 before boiling, after boil it ended up with around 40 liters and with a gravity of 1071, ready for fermentation. It means around 5 liters of water evaporates during the boil.

2 - Turn on the oven (or other heat source) with a very high temperature and pay attention to the beginning of the boil, when bubbles appear in the vessel. Now start counting the time. The boiling should be as intense as possible, but avoid evaporation greater than 15% (and less than 10%). In other words, an intense boil for a long time might be too much and a short and not very intense boil might be too little.

5 - Hop after the "Hot Break" just to avoid the aforementioned Boil-Over. Remember to add it so that it reaches the desired IBU.

6 - During boiling add the hops, spices, aromatic hops and whirfloc or any other items exactly according to the recipe, folowing exactly the "add-time" and quantities of each ingredient. To add the hop and spices it can be used a "hop bag" in order to avoid increasing the trub. The material will stay in the hop-bag. Depending on the bag it can reduce the final IBU. Trying and error would be the best choice to know how much it is affected.

7- After boiling, triple the care with cleaning and sanitizing after all your beer will be much more vulnerable to any type of contamination!

8 - Case BIAB method is not used, right after the heating source is turned off, with the brewing spoon, make a strong and circular movement in the wort. This is the "whirpool" for the trub to decant in the center of the pan.

The right time to boil the wort

The boiling is a process that must be well - controlled time and temperature.

Boiling is essential to sterilize the wort, isomerize the alpha acids and to make volatile compounds evaporate. It is a process that cannot be neglected and errors in time or temperature can "damage" all production.

In general, sterilization is achieved with about 10 minutes of boiling. The isomerization of alpha acids and iso acids is possible with another 60 minutes of boiling. The elimination of volatile compounds (DMS) depends on a vigorous boil and 60 minutes is indicated to reach this result. Before that, the beer can taste like boiled corn. However, in some beer styles, this feature is accepted.

This would be the ideal time to achieve the objectives of the boil. However, some recipes use more time, as they use this process to obtain other objectives, such as obtaining or reducing bitterness in beer.

Modern beer recipes or those with little hops, for example, do not need such long boiling processes.

In addition, in the boil the characteristics of color and flavor of the beer are defined and this will depend on the time that the wort will boil. Some beers, which need to taste more malt , for example, need to be boiled longer.

The complexity of the malt's characteristics is also influenced by the malt's boiling time.

If the goal is to have a more complex beer, with more pronounced and characteristic flavors and aromas, the wort must be boil for longer. In that case, 90 minutes is a good base to follow.

Now, if the goal is not to have such a complex beer, just follow the time indications that are suitable for achieving the objectives of the boil.

Thus, for simpler and less complex beers, 60 minutes of boiling. For more complex beers, 90 minutes of boiling.

Less than 60 minutes boiling indications in some recipes should be avoided.