Special Beers The Case For Pasteurization

“It doesn’t taste like what we wanted it to” was the quote used at a recall of a Bourbon-barrel aged beer that was infected with alcohol-tolerant Lactobacillus acetotolerans, a souring bacteria.

American brewers have pushed boundaries of traditional brewing with the development of barrel-aged beers, with previously-used wine barrels, bourbon and sprits barrels, and with installation of foeders (wooden beer tanks) in their cellars. Beers no one imagined 20 years ago are finding their fans and making names for the breweries that produce them.

Over 100 years ago, it was only the British who used unpitched wooden beer casks, and the special flavors of Brettanomyces were prominent in many ales of the times. In continental Europe and in North America, the use of pitched beer casks, (casks lined with a flamed-on resin) (a kind of natural plastic with a very mild taste and aroma), prevented beer from contacting wood and offered a smooth and cleanable surface.

Spirits casks expose the contents to direct wood surface contact. The uneven surfaces and spaces (pores within the wood) offer surfaces for microbial adhesion and colony growth. And with the fact that the surfaces are no longer flooded under spirits, one expects to find species including Zymomonas, Acetic acid bacteria, Candida, Zygosaccharomyces etc. present.

Belgian brewers flavor their lambics with cherries and raspberries to make kriek and framboise, and these classic styles served as inspiration for countless North American breweries. Innovative beverages based on natural cereal and berry products have gained consumer attention and may open new opportunities for the breweries. And the now-common practice of including loads of fruit in beers to deliver special flavors increases opportunity for undesired microbes to enter precious beer, often via species found on the skins of fruits. “Fruit” is a broad term with so much variety and also the form of the fruit. It is not uncommon for American breweries to add 8-25 lbs of fruit per barrel, and quite frequently, the addition is on the cold side.

The pasteurization process helps protect the general population from harmful foodborne illnesses that can be a problem for bottlers. Because heat destroys bacteria, it’s easy to use it to deactivate bacteria in a liquid. In beverage making, pasteurization stops the growth of yeast that remains in beer post-packaging. Breweries usually only have to worry about sterilizing canned and bottled beer. But with brewing infused drinks, that changes.

The pasteurization of bottles and cans happens after the package is sealed. This process involves running the bottler or can through hot water spray for the correct duration of time as dictated by the beverage and the bottle/can. 

What Are the Benefits of Pasteurizing Infused Beverages?

The benefits of pasteurization far outweigh the costs.

Reduces Over-Carbonation 

Infusing beverages with CBD, fruit and other ingredients in beverages can affect carbonation levels. Some microorganisms produce excess CO2. Pasteurization prevents the over-carbonation by reducing the organisms before they can cause too much havoc. 

A popular type of pasteurizer is the tunnel pasteurizer because it can offer high throughput and aseptic conditions do not need to be maintained downstream, as the beverage that has been pasteurize is sealed inside the bottle or can.

Tunnel Pasteurization Process

Pasteurization was developed by Louis Pasteur around 1864 and has been used in the beer industry since the nineteenth century. It refers to the reduction of microorganisms in beer or other foods by heating to a regulated temperature for a specific time in order to minimize the effect on physical stability and flavor while maximizing biological stability (1). Various organisms in beer are not pathological but affect the taste of beer (2). Draft beer is kept refrigerated and usually consumed in a short period of time, however, can and bottle beer is pasteurized for a long shelflife (1,3,4).

The shelf-life of beer has become a critical issue since it is one of the most consumed fermented beverages in the world (5). Beer’s shelf-life is determined by several factors including its microbiological, foam, colloidal, color, and flavor stabilities (6). Several months are possible if common contaminants are inactivated (7,8). This requires a pasteurization process at a time temperature of around 60°C (140°F) for about 20 minutes as stated in the book “Brewing: Science and Practice” by Briggs, Boulton, Brookes, & Stevens (9). Heat treatment of beer is currently done by flash pasteurization, batch pasteurization, or by tunnel pasteurization in the form of bottles and cans already sealed (10). Tunnel pasteurizers are an important procedure in the brewery packaging line (11).

Tunnel pasteurization occurs by traveling the cans or bottles through a tunnel that consists of progressively higher temperature zones, holding zones, and progressively cooler zones (12). Tunnel pasteurizers comprise a long, enclosed chamber, typically 15 to 30m, in which water sprayed onto the packages controls the temperature; the packages are moved through by a conveyor in the tunnel and is divided into 3 to 12 spray zones (13). The zones are divided into a heating zone where the temperature is progressively increased; pasteurization zone, where the product reaches the desired temperature; and cooling zone(s), where the packages are cooled to reach the desired beer out temperature (BOT).

The system includes a shell, tube heat exchangers, regeneration, and steam water heating. The water running off the packages falls into reservoirs and is recycled to the sprays. Tunnel pasteurizers use a single or double deck, nevertheless, the single deck conveyor has become more prevalent in the brewing industry in the United States because the lower decks in the double set are more likely to be subject to blockage (1).

Brewers should consider that aspects such as bottle size, material and shape influence the specific pasteurizing conditions, such as residence time within the tunnel, to achieve appropriate results (13). If pasteurization reaches a beer temperature too high from the desired level, flavors called “pasteurization tastes” may develop in the beer, along with alterations in the foam formation (15).

Water spray systems, including spray patterns, water volumes, and distribution systems, depend on the pasteurizer manufacturer (3). There are several options for elevating the product’s temperature to the adequate pasteurization temperature, usually using low and high-pressure steam or high-temperature water in either direct or indirect heating (5). The principles and effects of thermal preservation treatments such as this one are well established (6), and publications are widely available to delve deeper into the topic, such as the book Handbook of Brewing by Stewart & Priest (ed. 2017)(7).

The temperature at which water reaches its boiling point is a function of pressure; at atmospheric pressure, steam is created initially at 100°C (212° F). Interestingly, steam at 100°C (212° F) has a substantially higher heat capacity than the same amount of water at the same temperature.

This happens because when steam condenses on the surface of a cooler can or bottle, the latent heat of condensation is released on the surface as the steam turns from the higher energy gaseous state to the lower energy liquid state (8); producing a rapid rise in the surface temperature with little sensible heat change in the heating medium. However, high-temperature water can also be applied to beer containers by spraying or by deluging with cascading sheets or by immersion (7).

The heating of the water needed for spraying on the containers can occur by different means. Heat exchangers are often used. These exchangers contain fluids depending on the requirements, such as saturated steam, heated water, and others(9). The heat needed to pasteurize can be obtained by different options such as direct fire, gas-fired boilers, and electrically heated boilers.

In a low-pressure boiler, the pressure does not surpass 15psi while the temperature stays below 121°C (250° F). This type of boiler does not need constant monitoring. On the contrary, high-pressure boilers heat steam more than 15psi, and temperatures exceed 121°C (250° F). High-pressure boilers must have a boiler operator on staff to constantly monitor valves, switches, safety devices, or leaks.

Some manufacturers recently have adopted a centralized heating system (2). This system involves a single heat exchanger for all areas subjected to temperature control, providing heating a quantity of water maintained at a sufficient temperature for mixing with the process water of various areas depending on each area’s needed temperature. In this way, thermal energy is distributed by masses of hot water added in the different areas where a rise of temperature is required (Panella & Pasoli, 2000).

Why Tunnel Pasteurize New And Emerging Beverages

Food Safety in beer was once focused on undesired foreign materials and debris found in individual beverages cans and bottles. While still important, Food Safety in beverages today is mostly microbiological because breweries have moved far beyond producing only traditional beers.

We all know of examples of production and beverage sales environments where products are made, sold very quickly and in a tight geography…premises such as brewpubs and local neighborhood breweries which can offer a promise of freshness and competent storage of product between production and sale/consumption. But for any volume, sales must extend further, and quality must be assured for longer timeframes and across varying real-world conditions.

Breweries today produce beers mixed with fruit juices, and natural sodas, and low alcohol, sweetened beverages appealing to non-traditional beer drinkers. We’re also seeing novel cannabis-isolate containing hybrid beverages, These new drinks offer fewer naturally-inherent microbiological hurdles for spoilage organisms.

Due to novel ingredients previously not involved in production, beverages need to address concerns over germination of spores, and the growth of pathogens and other spoilers not routinely encountered in the brewing industry. The pasteurization parameters to destroy the vegetative cells and spores of Bacillus spp. are higher than what is normally accepted as adequate for milk pasteurizing…. 170 deg F at ten minutes hold.

The most common spoilage organism of tomato juice, B. coagulens produces lactic acid in package if not destroyed. In pineapple nectar, Byssochlamys nivea is a thermal resistant filamentous fungi (mould) with mycotoxin-producing potential that needs high sterilizing temperatures equivalent to tomato juice. Not every alternative product requires as aggressive a pasteurizing regime, of course. There are some new products, such as cold-brew coffees, that actually should go through much higher retort temperatures because the individual coffee beans, when dropped on the ground can make contact with botulism. Basic beer pasteurization does help cold-brew coffees and other novel beverages in an essential way:

Coffee with residual sugar is prone to refermentation or spoilage and can easily become a problem. Canned and fermenting coffee creates alcohol and carbon dioxide. That CO2 will continue to build and the can will explode or, in the case of a bottle, the cap/crown might pop off.