Pasteurization
What is Pasteurization?
Pasteurization involves heating a product in order to achieve greater microbial stability. For beer, there are two main types of pasteurization: flash pasteurization and tunnel pasteurization. Flash pasteurization involves passing the beer through a heat exchanger inline, to heat and then rapidly cool the product to achieve reduction in the concentration of viable microbes. Tunnel pasteurization involves passing packaged product through a tunnel that has a heated section and a cooled section, to achieve heating and cooling of the packaged product. In general, tunnel pasteurization is safer for sensitive products such as non-alcoholic beer.
How much do I need to pasteurize?
The brewing industry typically measures the amount of pasteurization needed (time and temperature) using a unit called Pasteurization Units. This in turn is based on the D value and Z value of the specific microorganism that the process is intending to inactivate, as different bacteria and yeasts have different D and Z values. Usually, the objective is to reduce the number of microorganisms by a specific order of magnitude - also known as "log reduction". Depending on the product you may target a different level of log reduction.
What impacts pasteurization required in beer?
Pasteurization Units required depends on several other variables in your beer, including the alcohol content (ABV) and bittering units (IBU) of your beer.
These are some general recommendations for Pasteurization Units required for different types of beers (from Rachon and colleagues):
| Beer | IBU | PU |
| Non alcoholic beer (0.0% ABV) | 8 | 83 |
| Non alcoholic beer (0.0% ABV) |
25 | 57 |
| Non alcoholic beer (0.0% ABV) |
50 | 41 |
| Standard beer (4.5% ABV) | 6 | 14 |
| Standard beer (4.5% ABV) |
25 | 12 |
| Standard beer (4.5% ABV) |
50 | 10 |
How much pasteurization is required to inhibit diastatic yeast (diastaticus)?
In general diastatic yeast strains have been shown to have a similar D value as standard brewing yeasts, although they have been shown to gain heat resistance over multiple cycles. This means that resident diastatic yeast contamination can be a potential problem area in a pasteurization program.
Resources:
Understanding Pasteurization Article
PU Calculator
Paper by Rachon and colleagues calculating D value, z-value, and PUs required to pasteurize brewing bacteria
Poster by Rachon and colleagues showing Pasteurization dependency on beer IBU content
Paper by Suiker and colleagues showing heat resistance acquirement of diastatic yeast