Can Liners: The Hidden Quality Barrier
Brewing has swiftly moved beyond beer production in the last decade, constantly pushing the edge of innovation to satisfy the diversifying desires of a consumer base that has interests beyond alcohol. From hazy IPA to hop waters to cannabinoid infused beverages, there is one critical component to success that is frequently overlooked: the can liner. These invisible barriers inside aluminum cans are meant to ensure product integrity, safety, and shelf-life, but not all liners for liquid libations are the same. In this article, we break down the basics of can liners, their types, and beverage-specific testing that helps avoid costly recalls, flavor degradation, etc.
Types of Can Liners
Can liners are thin polymer coatings applied to the interior of beverage cans to separate and protect both the metal and the beverage.
- Epoxy-Based Liners are traditional and known for durability. They may include bisphenol A (BPA*) or BPA-non-intent (BPANI) formulations. They tend to be the most suitable for most beers, soda, and low-ph products.
- Polyester (PET)-Based Liners are a BPA-free alternative for acidic or flavored drinks.
- Vinyl-Based Liners are flexible and inexpensive, but may interact with ingredients like essential oils and cannabinoids.
- Acrylic-Based Liners are used for water and soft drinks with lower chemical resistance.
Choosing the right liner is going to depend on what is being packaged and there are certain things that can be checked to help assess compatibility with the product lines.
*There are concerns presented on the continued use of BPA in products. Please consider the risks associated with this chemical prior to choosing products containing it.
Types of Beverages and Recommended Tests
Beer and Hard Seltzers
These beverages have a low pH and an alcohol content that can interact with liners over time, especially in sour or fruited variants.
Recommended tests:
- pH
- Titratable Acidity (TA)
- Alcohol by Volume (ABV)
- Dissolved Oxygen (DO)
- Chloride and Sulfate levels
- Stability testing
- Sensory testing
Hop Water and Other Acidic NA Beverages
These beverages have a lower pH (usually below 4.6) and a lack of the natural preservative ethanol, which can challenge liner stability and encourage corrosion.
Recommended Tests:
- pH
- TA
- Chloride and Sulfate levels
- Stability testing
- Sensory testing
Cannabinoid Emulsion-Based Beverages
Cannabinoids like tetrahydrocannabinol (THC) and cannabidiol (CBD) are lipophilic. Essential oils and these lipophilic compounds can absorb into liners, causing them to lose potency and break down the liner.
Recommended tests:
- pH
- Potency
- Stability testing
- Sensory testing
Some Final Sips
Can liner incompatibility can lead to many problems with a beverage, from off-flavors to even some safety recalls. With the rise of novel beverages, proactive testing and reviewing packaging specifications from the canning manufacturer will prevent many future problems and keep consumers happy, increasing brand loyalty.
Additional Resources:
Understanding the Complex World of Can Liners
The Secret Life of the Aluminum Can, a Feat of Engineering
Corrosion of aluminum for beverage packaging in acidic media containing chlorides and copper ions
Quality of organic coatings for food cans: evaluation techniques and prospects of improvement
Corrosion Performance of Aluminum and Stannum as Beverage Packaging
Binding of volatile aroma compounds to can lining with different polymeric characteristics
Need for Sustainable Packaging: An Overview
Food and beverage can coatings: A review on chemical analysis, migration, and risk assessment
Corrosion Behavior of Aluminium-Coated Cans
Bio-Based Coatings for Food Metal Packaging Inspired in Biopolyester Plant Cutin
Review on metal packaging: materials, forms, food applications, safety and recyclability