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Sterilising cold brew cans: How is it done? 

Cold brew cans have quickly established a strong presence in the fast-growing ready-to-drink (RTD) market. Thanks in large part to increasing RTD beverage consumption among millennials, the popularity of aluminium cold brew cans is growing fast. A report in 2023 projects that the global market for aluminium cans will be worth $92.31 billion by 2033. 

A myriad of reasons may be responsible for this growth. Aluminium cans are accessible and lightweight, they ship well and faithfully represent branding and product information. Beyond this, aluminium is infinitely recyclable and is one of the most widely recycled materials globally. This makes aluminium one of the most environmentally friendly and sustainable materials on the market.

However, factors such as food safety, shelf life, and flavour preservation present some of the cold brew sector’s biggest challenges. 

I spoke to several people in the industry, from researchers and coffee roasters to café owners and consultants, to learn how creative entrepreneurs have leveraged the advantages and limitations of cold brew cans to establish their market presence. 

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Cold brew cans: Balancing distribution, flavour, and safety

Sam Lopane is a researcher and food scientist, as well as a contributing author on a research paper that investigated the shelf life of cold brew coffee. When it comes to preserving the flavour of canned cold brew, he believes that “there are two worlds here.” What differentiates these two worlds, he says, is a matter of distribution. 

Brands can either seek national distribution or choose to focus on a local market. Therefore, distribution goals play a critical role in the choices available to preserve flavour. These choices can impact how a brand manages the safety of its product.

Cans were a natural choice for Eric Johnson, the CEO of Trident Brewing in San Diego, CA.  Trident’s marketing strategy targets a demographic that overlaps with the craft beer crowd in the region. As a result, he’s tailored Trident’s product and packaging to align with the aesthetics and values of the craft beer market, and aluminium cans fit right in.

“It’s a pretty big driver for the younger crowd to find ways to be more sustainable,” he says. “What’s nice about aluminium is that it’s one of the most recycled packaging styles.” Aluminium cans are also ideally suited to the nitrogen mixing process Trident uses to improve the mouthfeel of its product. 

Adding nitrogen during the fill process reduces oxygen in the can’s headspace. Removing oxygen lowers the rate of biological interactions, which, in turn, helps slow the growth of mould and bacteria. This contributes to increased shelf life while preserving the product’s flavour profile.

Distributing cold brew without heat sterilisation

Notably, Trident’s formula and canning process eliminates the need for heat sterilisation. The brand only offers straight black cold brew, with no milk, milk substitutes, or additional sugars, significantly reducing the risk of biological growth. Trident also maintains a full cold-chain throughout brewing, packaging, shipping, and sales. 

“We don’t do any pasteurisation,” Eric explains. “With our brewing methodology, filtration and nitrogen dosing, we get about five months of shelf life. That works really well for us to stay within the San Diego market.” He’s found that this method works best in preserving the flavour profile over time. However, these choices do limit the brand’s distribution. 

Once the brand is ready to expand to other markets, it will have to find ways to increase product shelf life. This will require the brand to develop relationships with co-packers or modify its formula, packaging, or sterilisation process. Another option would be to include additives that reduce bacteria and fungal growth. 

However, according to Sam, there are also trade-offs here. “The thing with black coffee is that there is nothing to hide behind. So if you’re adding a yeast or mould inhibitor, you’re probably going to taste it,” he says. 

Extending shelf life through hot fill pasteurisation

Another option for lengthening shelf life and widening distribution is to add some form of “kill step” in the form of heat treatments. Two of the most common heat treatments are hot fill pasteurisation, also known as High-Temperature Short Time (HTST) sterilisation, and a process known as “retort”. 

For HTST sterilisation, processors first pasteurise the coffee by heating it to 72ºC (161ºF) for 15 seconds. This will be hotter if the formula contains milk, sugars, or is concentrated. They then hot-fill sterilised cans in sterilised canning lines. According to a 2022 study, HTST had relatively little effect on the sensory quality of the coffee beverage and decreased the bitterness of the coffee.

Sterilising cold brew coffee cans using retort

Alternatively, retort is one of the most cost-effective and more common methods for sterilising cold brew cans. Retort canning processes do not require the beverage or the cans to be sterilised prior to filling. First, the cans are filled with the beverage and then hermetically sealed. As with Trident, brands will often add nitrogen just before sealing. 

Processors then heat the packaged product in a “retort” (also known as an autoclave) with steam and/or water at high pressure and at temperatures greater than 100°C (212°F) for 7 to 15 minutes.

The retort process is different from hot fill because it employs non-sterile products and hermetically sealed, non-sterile packaging. Retort exposes the product to higher temperatures for much longer than the hot fill process, and that can have adverse effects on flavour over time. Brands that rely on retort pay close attention to formulation and brew processes to compensate for these effects.

Different types of retort systems for cold brew cans

There are several types of retort systems, and they can be classified in many ways. Manufacturers classify retort systems as either still or agitating. In a still system, containers remain still, whereas an agitating system will turn or move the containers. Agitation can be particularly beneficial for cold brew formulas that contain milk or milk additives. Keeping the cans in motion can help prevent overcooking the product near the inner surface of the can. 

Retort systems are also differentiated by how products move through them: either batch or continuous flow. Batch systems process a fixed number of cans or pouches in a single batch, whereas continuous flow systems allow products to move through in a continuous line.

Different retorts also employ distinct heating methods: steam, full water immersion, and water spray. Each of these different types can have several variations, combinations, and capacities, each with tradeoffs in processing efficiency, energy consumption, carbon footprint, and cost. 

Therefore, it’s essential for entrepreneurs to consider the different technologies available and evaluate which retort method will best align with their brand goals.

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Where to begin?

As with many aspects of cold brew production, there is currently no single answer to the question of how best to formulate, sterilise, and package the product. The most important aspect of developing the product is to research the needs and expectations of the target demographic. 

Since 2018, Theo Garcia, co-founder of Solo Coffee in London, has been honing Solo’s combination of formula, processing, and packaging to suit the needs of his customers in the UK. “My advice to [those] starting out is look at what the leaders are doing,” he says. “Look for a product that is the closest to what you want to create, and try to reverse engineer it. 

“People are a bit scared thinking that competitors will make their lives really hard, but I think they’d be surprised at how much founders are willing to chat,” he adds. “I don’t think gatekeeping the knowledge around how you produce does anything for the category. In our case, in the UK, I think everybody wanted the category to thrive, and that [initiated] a ‘rising tide lifts all boats’ mentality.”

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About the author

Paul Clearfire is a coffee historian and author living in Portland, OR, and has spent the past 20 years perfecting the art of manual espresso extraction. He's been writing for Perfect Daily Grind Media since 2023.