The Science of Canned Beer
Since the 1930s, beer has been produced in cans. The initial cans were steel, looking more like a soup can than a modern beer can. They were opened by punching two holes in the top with a churchkey, and imparted a metallic flavor to the beverage. Soon, cone-top cans were invented that could run through a brewery’s bottling line. In the 1960s, pull tab cans gained popularity for their ease of use, but the tabs littered areas where beer was consumed and were dropped into cans, presenting a health hazard. In the 1970s, the stay tab can that we know and love today was introduced. Although the design hasn’t changed much since then, the material they’re made of has changed from tin or steel to aluminum coated in a food-grade polymer that minimizes the metallic taste the package used to impart.
Large breweries producing high volumes of cheaper beer were the only ones that were willing to pay for can lines for a long time, but that all changed in the early 2000s when craft breweries started to realize the benefits of canned beer. In the 16 years since the first craft brewery started canning, canned craft beer has grown to about a third of total package sales and continues to grow. Focusing on cans, lots of small breweries are growing in size and increasing can sales with their expansion.
The main factors that affect a beer’s shelf life and flavor are light, oxygen and temperature. Let’s dive in to each:
There are tradeoffs in light and oxygen between cans and bottles, each offering benefits in different areas. Clear and green glass offer very little protection from light. Brown glass is a preferred choice when using bottles, letting in a small percentage of light. Cans are made of opaque aluminum, keeping the liquid inside 100% safe of light. Why is this important? “Lightstruck” beer as we call it has a skunky flavor that is detected at very low levels. This flavor develops when UV light energizes hop compounds, causing a chain reaction that results in the compound 3-methyl-2-butene-1-thiol, or 3-MBT. This reaction happens very quickly; people sensitive to the aroma can notice even a draft beer start to pick up 3-MBT while they’re drinking it out of a clear glass on a sunny day. Since cans don’t allow any UV light to interact with the beer and cause skunking, this makes them a great vehicle for beer you’re bringing poolside on a summer day.
Oxygen is another factor that can impact the taste of beer. No matter how our beer is packaged, we are always looking for ways to reduce the initial amount of oxygen contained in the bottle, can or keg. Why? Oxygen can cause beer to present off-flavors of cardboard or dried fruit—altering the taste of the beer. A can lid is sealed tightly and will not allow oxygen transfer into or out of the container.
In order to make sure our beer is being packaged in the best way possible, there are a number of checks that are performed. Both cans and bottles have their total package oxygen (TPO) measured to make sure it is low and the level will not lead to the oxidized or old flavors. Both the amount of oxygen in the liquid and the amount in the headspace (the empty space above the beer) are measured and added up to get the amount of TPO.
The seam that runs along the top of the can is a twist of the body and lid that seals them together. Measurements are taken on the outside and inside dimensions of the seam to ensure the seaming is meeting the manufacturers specifications for a perfect seal. These measurements are recorded and tracked over time to make sure the seaming equipment is always functioning at its best, sealing out the air from the cans.
Fill volumes are another consideration of packaging quality, and since the liquid level is not visible in cans, other ways of measuring are utilized on the canning line. A very simple way to figure out the amount of beer in a can is to weigh an empty can, weigh a full can, and with the density of the beer the volume can be calculated. This cannot be applied to continuously monitor the fill levels of the cans moving through the packaging line, so a different measurement technique is utilized: gamma ray fill level detection. Using an in-line instrument to monitor fill levels allows every can to be checked for the correct volume, ensuring the customer is getting every last drop of goodness they deserve.
Keeping beer at refrigerator temperature for the life of the product is most desirable to keep degradation to a minimum. Skunking, oxidation, degradation of compounds and formation of compounds are all chemical reactions that speed up with an increase in temperature. Higher temperatures result in more motion of the molecules and therefore more likelihood they will collide and react. Since the temperature of the package is controlled by the retailer and consumer, there are no notable differences across packaging formats. However, consumers can make the choice to select from a fridge rather than a room temperature endcap, or from a store with ample cooler storage to give themselves the best chance of getting fresh beer.
Although canned beer has been viewed as a lower quality product for a long time, advances in the packaging material, filling techniques, and monitoring equipment has made canning a great option for packaging high-quality beers.
Track down our newest canned beers (Prismatic Juicy IPA, Yours Truly Easy-Drinking Ale and Pacific Rain Northwest Pale) by visiting DrinkNinkasi.com.
About the Author
When you need to know the nitty-gritty nerdy side of beer, Joe has your back. As Ninkasi’s Analytical Quality Specialist, Joe makes sure our beers are just as our customers expect each and every time. On Fridays, you’ll find him around the brewery sporting the latest trends in Hawaiian shirts. Any day of the week (especially during MLS season), you’ll find him watching a game with a Helles Belles in-hand.