Valuable Insights into Canned Food

Image credit: Author with Ai and Wei Cheng

In a world grappling with significant food waste, canned food stands out as an ingenious solution, offering extended shelf life without the need for preservatives.

In 2018, the newspaper Dagbladet declared the departure of canned food from shelves with a headline proclaiming the imminent disappearance of cans from stores, never to return.

There exists a common misconception that all canned food is packaged in metal tins, and it is also inaccurate to assume that all cans will vanish soon. The article highlights Unil and Coop's announcement that their respective canned brands are undergoing a transition to square cardboard containers from traditional round metal cans. This shift aims to enhance transport efficiency and consequently diminish their carbon footprint.

Canned goods equal metal tins? Wrong!

In Norway, many people commonly link canned food with traditional metal tins, particularly the large round ones often used for ready-made meals like fish balls, lobscaus (lobscouse stew), and spaghetti in sauce.

Image credit: Author with Ai

However, it's important to understand that canning is a method of food processing, irrespective of the container material. Whether you purchase chopped tomatoes in cardboard cartons or metal tins, both have undergone hermetic sealing. Nowadays, hermetically sealed food comes in various containers such as steel tins (for ready-made meals and vegetables) or aluminum tins (for mackerel in tomato sauce, sardines, liver pâté, tuna), sterilizable cardboard cartons, pouches (for sauerkraut), stand-up pouches (for sauces and soups), plastic cups (for ready-made meals and sandwich fillings), glass jars (for pasta sauce and baby food), and soft aluminum packaging (for mackerel in tomato sauce and cat food).

What unites all hermetically sealed food is the processing technology: the food is placed into suitable containers and sealed airtight against microorganisms. Subsequently, the sealed containers undergo cooking in a pressure cooker (autoclave) at temperatures ranging from 110 to 135 °C for a specific duration, ensuring commercially sterile products. This heat treatment aims to eliminate all vegetative bacteria and spores, including heat-resistant ones like Clostridium botulinum.

The duration and temperature of heat treatment involve multiple factors such as heat conduction within the food, container geometry and size, container material, and the heating medium in the pressure cooker. Additionally, the type and quantity of bacteria potentially present in the product must be considered. Any changes in these parameters necessitate corresponding adjustments in processing requirements. When executed correctly, this process deactivates enzymes and significantly extends the shelf life at room temperature (typically 2 to 5 years), achieving a level of food safety unmatched by other preservation methods.

Introducing new container types brings forth fresh challenges

Moving from metal tins to cardboard-based packaging, like Tetra Recart, requires significant investment and restructuring in production and processing. This involves acquiring new filling and sealing systems and adjusting autoclave trolleys for consistent heat distribution. Cardboard containers have lower surface conduction coefficients than metal, likely resulting in longer processing times. Square-shaped containers may also heat unevenly, risking burning at corners and edges. Regardless of the container, the process must ensure adequate heat distribution for food safety.

While various alternatives exist, none match the qualities of metal. Metal tins offer 100% airtight and lightproof sealing, providing several years of shelf life compared to alternative containers offering only 12 months. Some sardine enthusiasts argue that the product improves with age in metal tins. Additionally, metal tins are fully recyclable, like glass.

Nicolas Appert – Pioneer of Canning

In 1809, Nicolas Appert emerged victorious in a competition held in France, aimed at discovering the most effective method for preserving food over extended periods. This competition arose from Napoleon's imperative for a reliable food supply for his military forces, particularly those destined for deep incursions into Russian territory. Appert's innovative approach involved boiling food in sturdy glass bottles, promptly sealing them with wax post-boiling, enabling preservation for several weeks.

The subsequent year witnessed the introduction of the tin can, crafted from iron and coated with tin to thwart rusting, sealed with lead solder. The inaugural canning facility was established in London in 1813. Notably, this milestone occurred over 50 years before Louis Pasteur elucidated the link between heat and bacteria destruction. While the effectiveness of canning was widely acknowledged, the underlying mechanisms remained a mystery. Eventually, it became apparent that pasteurization alone did not ensure indefinite preservation, as certain spore-forming bacteria necessitated exposure to temperatures surpassing the boiling point of water to become inactive.

Canned food is here for the long haul

Amidst a world plagued by food waste, canned food emerges as a brilliant solution, offering extended shelf life without the need for preservatives. When food is cooked within a tin, the boiling water preserves its nutritional integrity, retaining most vitamins, polyunsaturated fatty acids, minerals, and overall nutritional value. Although some water-soluble vitamins like vitamin C may undergo slight degradation, the benefits remain substantial. Canned food has proven indispensable in disaster relief efforts, safeguarding countless lives, while the metal tin acts as a barrier against pests. Maintaining a small stockpile of canned goods serves as a prudent measure, whether for use during power outages or as a backup at remote locations like cabins. Evidently, the widespread acceptance of canned food is reflected in its global annual market growth of 3.8%.

The United States continues to grow its canned food market, especially for vegetables and ready meals. The trend is the same in the UK. Source: Grand View Research, 2018

Since its inception in 1931 as the "Hermetikkindustriens Laboratorium," Nofima has been dedicated to preserving food and assisting the Norwegian industry in finding optimal solutions for diverse needs. Our efforts have focused on developing innovative container variations for sterilized products, as well as preserving color, taste, and texture through gentler heat treatments. Techniques such as shaking, ultrasound, and microwaves have been employed to reduce processing time, while combining heat treatment with high-pressure methods ensures both food safety and extended durability.

While we may adopt a somewhat conservative stance, we maintain that canned food will continue to occupy space in future stores, alongside pasteurized, chilled ready-made dishes, and fresh products with shorter shelf lives.