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The Science of Pasteurization: A Guide to Pasteurization Control

Brewing beer is a balance of both art and science. Bringing together delicious ingredients and interesting recipes is crucial, but unless you have the scientific expertise to ensure your brew’s shelf life — you might not be making anything that will last.

Beer is the ideal home for several tiny organisms totally invisible to the naked eye. And if it isn’t stored correctly, you’re unknowingly creating an environment where microbes and other contaminants can cause infection. Exposing your customers to bad, or even spoiled, beer can mean big trouble for you, your brewery, and the reputation of your beer.

If you want to sell quality products that last on the shelf or in a consumer’s fridge, you need to pasteurize your product. Most commercially canned and bottled beers are pasteurized, but when it comes to smaller breweries and their operations — it doesn’t always feel like a viable option. In this guide, we’ll share some of the history and science of pasteurization, as well as why this process control might be the right answer for your brewery.

A Little History Lesson…

Before we get into the nitty-gritty details of pasteurization, here’s a quick historical recap that dates all the way back to the 1800s.

If you didn’t already know, pasteurization was invented by Louis Pasteur. His original work resulted in a process that keeps us safe from getting sick from bad milk. But it started with a study on spoilage prevention for beer (as well as wine), because brewers were looking for ways to keep their beer from going bad.

In 1864, Pasteur discovered that when you heat beer, it defeats spoilage caused by microorganisms, thus lengthening its shelf life. So, he then tested his theory with milk and history was made.

Pasteur even came up with a design for a controlled atmosphere wort process, which helps improve beer flavor and brewery yield. So, we’d say it’s pretty clear that Pasteur was a beer lover like the rest of us!

What is Pasteurization?

Pasteurization is a heat treatment process that primarily aims at destroying the pathogens present in beverages, thus minimizing the probable health hazards. In short, it refers to heating the product to kill most of the pathogenic microorganisms, followed by rapid cooling. This process typically happens before a product is shipped out.

This process differs from full sterilization because it does not completely eliminate all biological agents (bacteria, viruses, fungi, etc.). Rather, pasteurization is designed to use just enough heat to prevent spoilage while simultaneously minimizing the impact on the flavor and aromatic qualities of a product, and prolonging its shelf life.

Beer is pasteurized in two ways: flash pasteurization and tunnel pasteurization. Both have widespread usage. Flash pasteurization exposes the beer to a higher temperature for a shorter period of time. This is known as “high-temperature short-time” (HTSH) processing. Beer that has been flash pasteurized is then cooled rapidly before being filled into sterile containers.

Discover: Is flash pasteurization right for your brewery?

A tunnel pasteurizer exposes beer to a slightly lower temperature for a longer time period. The time and temperature effects on the beer are typically one of the major evaluation points when considering which technology is best for a brewery. Bottled and canned beers pasteurized through this method are passed through a long, relatively narrow chamber where hot water is sprayed over the containers before cooling. The spraying chamber is called a “tunnel” — hence the name. However, it’s important to note that heating the contents of the keg in a tunnel is impractical. Instead, beer is heat treated by being passed through a heat exchanger.

The main takeaway here is that pasteurization can be considered a balancing act of risk management and trade-offs. Too much heat can affect taste and aroma. Too little heat and you’ll have to deal with wasted product, spoilage, and a potentially costly recall. This is where accurate measurement comes into play, so you can make an informed decision on how much heat to use and how much time is right for your beer.

How Is Pasteurization Measured?

Pasteurization is measured in pasteurization units (PU) which are defined as the sterilizing effect observed for one minute at a temperature. This temperature is commonly known as the reference temperature (Tref). The sterilization increases exponentially with the temperature at a rate that is defined by the coefficient of thermal resistance (Z). There’s a formula that helps you calculate PU, and it’s:

PU = t * 10 (T-Tref / Z)

PU is a pasteurization unit

t is time (in minutes)

T is the temperature (in Celsius)

Tref is a reference in temperature (in Celsius)

Z is the coefficient of thermal resistance (in Celsius)

The PU equation essentially helps you to compare similar slight variations between process runs. For example, if a process calls for the pasteurization of a beverage at 63°C for 30 minutes the PUs can be calculated for the process before it takes place.

When the real process is run, which will see variations in temperature and time, the data can be easily analyzed and compared with the guideline for more efficient and effective process control.

The number of PUs applied will vary, depending on the risk of spoilage of a specific beer, but for most beers, the range is 5-25 PUs, with 15 PUs being about industry standard. Beers with a very low alcohol content will tend to receive more PUs.

The Great Pasteurization Debate

Pasteurization aims at increasing the safety of a beverage by increasing its freshness and shelf life through quality control. Heat-treated beverages can often sit without refrigeration for months, which is critical when considering distribution and possible shipping delays.

A common debate about pasteurization within the industry is whether the process changes the flavor of the beer. One side of the debate insists that heat pasteurization robs the beer of flavor, while the other side holds that there is no discernible effect on the flavor.

But there has been no extensive research yet on pasteurization’s impact on flavor. It’s really dependent on whether or not a craft brewery has the space and funds for the necessary equipment.

When a brewery becomes big enough, it will likely pasteurize its products regardless of what side of the debate they were previously on to ensure that it can distribute out-of-state.

Guidelines for Considering Pasteurization

When considering an equipment purchase for pasteurization, a brewery will need to evaluate six main factors. Here’s a list of some of the most important guidelines:

1. Cost of Equipment

Flash pasteurization is a long-term investment, because of the technology and advanced equipment involved. However, many models have become more affordable over time, and compared to the capital costs of a tunnel pasteurizer, a flash pasteurizer is a more economical option.

2. Equipment Size

A flash pasteurizer is much more compact than a tunnel pasteurizer, which makes it the right choice for breweries with a limited footprint.

3. Installation

Installation of a flash pasteurizer is relatively easy due to its size. With a tunnel pasteurizer, installation may require more site work, time, and equipment which will drive up costs.

4. Quality Control

A flash pasteurizer requires rigorous quality control before and after to ensure safety and quality. For many breweries, this may mean expanding your team but fortunately, you can leverage advanced monitoring systems to help automate and expedite the pasteurization process.

5. Effectiveness

Flash pasteurization is the only viable option for highly perishable beverages like beer. Especially when brands want to extend their product’s shelf life without compromising on taste.

6. Cleanliness and Sterilization

When using a tunnel pasteurizer, beer is packaged before the pasteurization process. With flash pasteurization technology, there are added factors of cleanliness and sterilization to consider. The downstream holding tank has stringent cleanliness standards and the filling equipment must be sterile to prevent any downstream contamination.

The Key Takeaway

Whether you choose to tunnel or flash pasteurization, you should have one goal in mind: ensuring the shelf life of your product, so you can get it into the hands of beer lovers across the country (maybe even the world). Pasteurization is the answer, and with accurate measurements, an understanding of the importance and effectiveness of the process, and consideration guidelines — it’s much easier to make an informed decision on what is best for your brewery.

Get Started with Shelf Life Systems

Is your brewery considering pasteurization but unsure of where to start? Sounds like you need an experienced, reliable pasteurization partner to help you ensure the process’s efficacy and safety.

Don’t leave your best beer’s shelf life to chance. Get in touch with the Shelf Life Systems team today to learn about our options for pasteurization process control, and how we can help you maximize your beer’s shelf life.