Lesson 4 - Wort Boiling Technology and Process Control

High temperature wort boiling (HTWB) is a continuous system where unboiled wort is pumped continuously in one end and boiled wort flows continuously out the other.

Boiling at a higher temperature means that many of the requirements of boiling can be achieved more quickly. For example, at 130-140°C the isomerisation of hop acids can occur in five minutes.

The wort is heated up in three steps:

• Wort from the lauter tun is collected in a collection vessel where hops are added and the pressure is increased to six bar.
• The wort is then moved through a series of heat exchangers that heat it to 95°C, then 115°C via a second heat exchanger and finally 140°C.
• It is then pumped through a section of coiled pipe, taking 5 minutes to flow through this section.

Finally, the wort flows into a pressure release vessel, where the pressure drops to one bar and around 120°C. It then flows into a second pressure release vessel, when the pressure drops to atmospheric pressure and 100°C.

The drop in pressure causes a massive release of vapour and this is used to heat the incoming wort. Although evaporation rates can match batch systems, volatile removal is not as effective. Other requirements of the boil like protein coagulation are also achieved less well in high temperature boiling systems. Oxidation and colour pick up is however less.

HTWB is designed to work in a continuous brewhouse system. If we need to store wort produced in batches in a tank before we process, we can encounter the following problems:

• If wort is stored hot (> 85°C), colour can increase and undesirable flavour changes can occur.
• If the wort is stored cool (< 35°C), it is prone to microbiological infection.

Since almost all brewhouses are batch systems, high temperature wort boiling is not widely used and high temperature boiling systems are no longer manufactured.