To Boil or Not to Boil
Given that malt extract has already gone through a brewing cycle, many brewers have questioned the amount of additional processing that must be done to successfully brew beer from extract. Specifically, the question of whether worts made from extract require boiling often arises. Understanding their manufacturing process and the main goals of boiling malt extract provides the answer.
There are 5 main “-ations” that brewers are concerned with when boiling their wort or concentrated worts. These are:
Carmelization (of sugars)
Volatilization (of DMS precursors)
Sanitation
Coagulation (of proteins) and
Isomerization (of hops)
Carmelization and Volitization:
Brewing- grade extract has already undergone a kettle boil and extensive volatilization. Beneficial colors and flavors have been developed from carmelization and Maillard reactions in the kettle boil. Any volatile off aroma or flavors from the grain or DMS precursors have been removed. If the extract is diluted to wort and held at boiling temperatures without proper additional volatilization, additional precursors can be generated. In general, worts from malt extract do not need to be boiled to remove DMS precursors. However, if they are boiled, the boil must be vigorous enough to remove these precursors as more are created when wort is held hot.
Coagulation:
All brewing-grade manufacturers remove hot break from their malt extracts. Some manufacturers also remove the cold break.
Sanitation:
Though not a sterile product, brewing grade malt extract has gone through a boiling step and has a very low microbial count. It exists as a low water activity product, not permitting growth or spoilage. Contamination is normally so low that simple pasteurization of wort at 160 ºF (71 °C) for 2–5 minutes is enough to provide reasonable assurance of an uncontaminated finished product. Thus, if using a hopped malt extract or hop extracts, brewers can get away with very short or nonexistent boils, depending upon hop aroma desired and confidence in yeast and sanitation.
Isomerization:
Boiling is necessary to isomerize the alpha acids in hops in order to make them soluble. If you are brewing with unhopped malt extract, you will need to boil your hops in wort. However, you can withhold a sizeable amount of your malt extract and add it late in the boil or at the end of the boil.
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