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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 on pasteurization is most known for the process that helps keep us from getting sick off spoiled milk. But did you know it started with a study on spoilage prevention for beer (as well as wine)? At the time 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.

Pasteurization is different from sterilization because pasteurizing a beverage like beer doesn’t kill all of the bacteria or other microbes. Instead, the process uses just enough heat to prevent a beverage, like beer, from spoiling while retaining its flavor and prolonging its shelf life.

Beer is pasteurized in two ways: flash pasteurization and tunnel pasteurization. They both have widespread usage in the food and beverage industry, as well as pharmaceuticals and more. Flash pasteurization consisted of heating beer to a high temperature but for a short period of time. This process is commonly known as “high-temperature short-time” (HTSH) processing. Beer that has been flash pasteurized is cooled rapidly before being filled into sterile containers like bottles or cans.

Discover: Is flash pasteurization right for your brewery?

A tunnel pasteurizer heats beer at a slightly lower temperature but for a longer time period. Bottled and canned beers pasteurized through this method are passed through a long, narrow chamber. Hot water is sprayed over the bottles and/or cans before they are cooled. The spraying chamber is called a” tunnel.” For most breweries, using a tunnel pasteurizer for kegs is impractical because of their size. Kegs large size can interfere with the heating and cooling of the beer inside.

The main takeaway here is that pasteurization is often a balancing act. The time and temperature effects on the beer are typically one of the major factors when considering which pasteurization process is best for a brewery. Too much heat can affect taste and aroma. Too little heat and you’ll have to deal with wasting product, exploding cans, and a potentially costly recall. This is where accurate measurement comes into play. Accuracy allows you to determine how much heat to use on your beer and for how long.

How Is Pasteurization Measured?

Pasteurization is measured in pasteurization units (PU). PU is defined as the sterilizing effect observer for one minute at specific temperature. This temperature is the reference temperature (Tref). Sterilization will increase with the temperature at a rate 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 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 varies. It depends on the risk of spoilage of a specific beer. For most craft beers, the range is between 5-25 PUs, and 15 PUs is considered an industry standard. Beers with lower alcohol content often have 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.

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