Inline pasteurization

This page includes some information about a flash pasteurizer and it’s use, a calculator to see how much regeneration effect an existing plate heat exchanger (PHE) is actually providing, and another calculator to see how much money in terms of heating and cooling energy a certain regeneration percentage translates to.

A flash pasteurizer has not been having a great image in the craft brewing world. The thermal treatment is seen as detrimental to the beer, and non pasteurized beers seem to be a must for most of the craft breweries.

What does a flash pasteurizer do?

Traditional use:

A flash pasteurizer will treat thermally the product inline for a short amount of time and therefore apply a certain amount of pasteurization units (PU) in order to kill some potential micro organisms (MOs). The product is then cooled down right after. The applied PU is usually around 10 to 25 PUs but can go up to 100 if the brewer feels the need. In Germany, it is also used to stabilize the haze in heffe weisse beers. In that case, the thermal impact is much higher than the above mentioned values.

Hop creep:

The hop creep affecting brewers dry hopping their beers can be controlled with a flash pasteurizer, apparently by applying a PU as low as 1 – 2 on the beer. This seems to be enough to denaturate/inactivate the enzymes responsible for it and get rid of the adverse effects.

What a flash pasteurizer does not do:

It cannot take care of a contamination happening after its outlet. This means that if there is a contamination risk in the filling area, or if the cans or bottles can carry some contaminants, a flash pasteurizer won’t help. In this case, a tunnel pasteurizer has to be considered.

What about the impact on beer quality?

If done the right way, the thermal impact should be difficult to be perceived. If the beer has a rather high level of O2 (close to 100ppb and above) before to enter the flash pasteurizer, it can trigger an accelerated oxidation of the beer and therefore accentuate the perception of “pasteurized” flavor. If the O2 is low and the applied PU is in normal range, it shouldn’t be that easy to taste whether a beer has been flash pasteurized for a non trained person.

When/why to use it?

  • If a brewery has shelf life issues related to microbiological issue, and the source us upstream.
  • If there is over carbonation because of hop creep – a thermal treatment could help denaturate the enzymes and neutralize the remaining yeast.
  • You’re making heffe weisse and would like to have it stabilized.

How does it look?

The main compound of a flash pasteurizer is a high pressure plate heat exchanger (PHE) made of 3 sections (or 3 separate PHEs):

  • A cooling section
  • A regenerative section
  • A heating section

The beer to be pasteurized enters via the regenerative section to recover the heat from the pasteurized beer to be cooled down (beer that comes in cools down the beer that comes out).

The preheated beer enters then the heating section to be brought up to pasteurization temperature. It then enters the holding cell and is kept under high pressure to avoid CO2 breakout.

It is then entering the other side of the regenerative section of the PHE to be cooled down by the beer coming in.

The pasteurized beer leaving the regenerative section is entering the cooling section to be cooled at the final desired temperature.

What to pay attention to when looking for one?

Hygienic design

Such a system is used to solve contamination issues happening upstream. Contamination issues can happen because some parts of the installation are difficult to or no entirely cleaned because of a sub optimal design. It is therefore important to go for a system that has been designed and build in a hygienic way: Sanitary connections, sanitary pumps and valves, no dead ends in the piping..

Made for beer

There are many flash pasteurizers that claim they can handle beer or carbonated products. It is important to make sure the company offering one has experience in such application and is able to hold within the PHE and the holding cell high pressures up to 12 barg (~174 PSI) in order to avoid any CO2 breakout during the pasteurization phase. If such thing would happen, very bad heat transfer, foam in the PHE, creating difficult to remove fouling on the plates, degassing in the whole phase when the beer is hot.

Energy recovery

The flash pasteurizer (or more specifically the PHE) will come with a rate of energy recovery. It usually ranges between 90 and 95%. The closer we get to 100%, the more plates the PHE needs to be equipped with. It is not linear and therefore not possible to reach 100%. The price will also be impacted by this since the PHE will require more plates. It could be tempting to go for the option that gives a higher energy recovery rate, but it is sometimes not worth the money since the pay back time could be quite long.

The below calculator gives an idea of the recovery rate of an existing system based on the temperatures at the different inlets and outlets of the PHE. It also gives an idea of the energy consumption on the cooling and heating duty. This gives a better overview of what is the real running cost of such system (beside the electrical consumption).