Fermentation Riot All Grain Beer Brewing

Purpose of Wort Boiling


The purpose of wort boiling "boils" down to these main items:

Removal of volatile off flavors.
Sterilization and enzyme destruction
Formation of Protein and Tannin precipitation
Extraction of hop constituents and isomerization of hop acids
pH reduction
Increase in color
Decrease in surface tension

Wort Boiling

If you often overlook your boiling process you might want to reconsider after reading through the information in detail below.

Often the wort is diluted following lautering which must be concentrated to reach the set original gravity. Boiling will often achieve a 5-10% rate per hour.

Removal of Volatile Off-Flavors:
Many volatile substances are present in the wort after lautering which must be evaporated. These include DMS (di-methyl-sulfide) from the malt, other malt related volatiles, and undesirable hop volatiles. As overall hop aroma is volatile this is why it is added into the wort by late additions.

The temperatures of the malting process are not quite high enough to inactivate the microorganisms and microflora which originate from the malts used. Therefore, boiling for 15 minutes (minimum) is needed to inactivate all organisms. As bacteria can quickly contaminate a good batch of wort it is extremely critical that the batch be cooled from boiling and placed in a sanitized fermentor as quickly as possible.

Break Formation:
Hot break is a visual indicator (usually frothy foam on the top of the wort) which indicates that proteins are being denatured. During this process the protein becomes hydrophilic and takes on a positive charge. Polyphenols often have a negative charge and combine with the positive protein structures. These can often be manually scooped from the surface of the boiling wort and removed.

Hop Isomerization:
During the boiling process hop components are solubilized and the oils which are very harsh are immediately evaporated. Alpha and beta acids are solubilized in the wort and during this process the alpha acids are slowly isomerized which contributes to the bitterness of the beer (IBU rating). The longer the acids are exposed and the higher the acid content at boiling temperature, the higher the bitterness of the beer.


What are the impacts of not boiling vigorously enough or not long enough?

Lower gravity, larger fermentation volume, insufficient hot break, poor fermentation, haze generation, premature chill haze formation, higher DMS levels (unless you like vegetables), and poor hop utilization.


What are the impacts of boiling too long?

Higher gravity, lower volume, trub breakup and redistribution which results in haze and flavor problems, excess maillard reactions (bready and cardboard flavors), harsh bitterness, and increased wort and beer color.


In the end it is important to understand the beer style at hand and the time needed at boiling to satisfy your recipe requirements. Hope this helps...





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