Lesson 5 - Wort Boiling Technology and Process Control SAQ

**Your brewery has two kettles. The heat transfer data for each are shown below. Which kettle will produce the most stable beer?

Kettle 1

Rate of heat transfer is 4630 kW/hL

Heat transfer coefficient is 1.3 kW/m²/K

Heater surface area is 100 m²

Kettle 2

Rate of heat transfer is 4630 kW/hL

Heat transfer coefficient is 1.0 kW/m²/K

Heater surface area is 180 m²

Response:

The question is asking about beer stability. Beer stability comprises of colloidal, flavour and foam stability. Flavour and foam stability are both reduced by high ΔT. Therefore, we need to determine which kettle has the highest ΔT. To do this we use this equation.

So, for kettle 1 we can calculate ΔT:

The difference between two temperatures in Kelvin is the same as this difference in centigrade, so our ΔT for kettle 1 is 35.6°C.

And for kettle 2:

So, our ΔT for kettle 2 is 25.7°C.

As higher ΔTs result in beer with poorer foam and flavour stability, kettle 2 is likely to produce more stable beer in terms of flavour and foam. With colloidal stability it is difficult to assess this based solely on these data. If we had to guess, kettle 1 would be our best bet because trub formation occurs faster when more thermal energy is supplied. Analysing samples of the beer produced by each kettle would be necessary to definitively determine which produced the most colloidally stable beer. This would also be wise for assessing foam and flavour stability!