The invention of the canning process 200 years ago is undoubtedly one of the most important developments in food packaging history. It began innocuously enough in the late 1700s when Frenchman Nicolas Appert (lured by Napoleon Bonaparte’'s promise of 12 000 francs to the first person who could preserve food for his army) applied heat to food sealed in bottles, inventing a method for safely conserving food without refrigeration.

The invention of the canning process 200 years ago is undoubtedly one of the most important developments in food packaging history. It began innocuously enough in the late 1700s when Frenchman Nicolas Appert (lured by Napoleon Bonaparte’'s promise of 12 000 francs to the first person who could preserve food for his army) applied heat to food sealed in bottles, inventing a method for safely conserving food without refrigeration.

At that time, food spoiled easily and Nicolas experimented with various packaging techniques, discovering that food would last longer when sealed in an airtight container and soaked in hot water for a few hours. He closed bottles and jars with cork, wire and sealing wax to keep air out. Legend has it that, having discovering the key to protecting food, he received his monetary reward after Napoleon’s troops enjoyed the freshness of his bottled partridges, vegetables and gravy!

Nicolas Appert built a bottling factory to continue supplying preserved food and this was followed in the early 1800s by Peter Durand who adopted his process to foods packed in tin-coated steel canisters, and patented the method in 1810.

The tin can was a major revolution, making heat preservation practical since metal containers proved to be more suitable than glass for filling, sealing, heat processing, storage and distribution. Bryan Donkin and John Hall developed the process further, setting up the first commercial canning factory in England in 1813, supplying canned food for the military. Initially only reserved for the very wealthy or sick sailors at sea, demand for tinned food greatly increased during the 19th century wars.

Heating foods in hermetically-sealed, tinned steel containers formed the basis for the first convenience foods and marked the start of the canned food industry, opening the market for shelf-stable, canned products.

That the invention of the canning process is one of the most important developments in food packaging history is borne out by figures from local market intelligence organisation, BMI Research, which estimates the local metal can market value at R4,3-billion for 2009.

The canning process and safety

Although canning technology has improved over the years, its core principles remain as relevant today as they were 200 years ago.

Foods are packed at peak freshness (reducing nutrient loss) with sufficient heat applied to sealed, airtight containers to reduce micro-organisms to an extremely low level.

Processing times differ according to the type of food, its density, acidity and ability to transfer heat. Once cans are sealed and heat processed at temperatures of 116 to 121°C, food quality is maintained for more than two years, so long as the containers remain undamaged.

The sequence in the canning process differs according to each product, with some food receiving heat treatment before being placed in the can.

According to a 1997 University of Illinois study, the canning process may help enhance the nutrient level of some foods. Canned pumpkin, for example, contains 540% of the recommended daily intake of vitamin A, while the same amount of fresh pumpkin has only 26%.

Today, thermal processing of ready-to-eat foods is at the heart of food processing in terms of preserving and enhancing food’s flavour, texture and colour. It offers several advantages over non-thermal processes: it does not compromise food’s sensory and nutritional qualities and produces safe, high-quality and shelf-stable products.

As a thermal processing authority, Nampak R&D, acknowledged as one of the world’s foremost packaging research and development institutions, has trained thermal processing specialists who work directly with Nampak DivFood, the leading food can supplier to the Sub-Saharan canning industry.

‘Through Nampak R&D, Nampak DivFood offers customers expert knowledge of thermal processing requirements for foods packed in hermetically-sealed containers as well as providing access to the right facilities to make process determinations. "This is a vital ingredient for any can of food, and a must-have for canned food suppliers,’" comments Nampak R&D’s general manager, Johan Visser.

He goes on to explain that, because foods differ, each specific food-type needs its own thermal process. "Determining this scheduled process with the proper temperature and process time needed to produce commercially sterile products is where Nampak DivFood offers customers real added value. Even if the type of starch used to thicken the tomato sauce in a product (such as baked beans) is changed, this could affect the thickness and heating properties of the sauce and thus the thermal process must be re-established to provide consumers with a safe product,"’ Johan adds.

Material developments

One significant difference in the modern canning process is that today’'s cans are made of 100% recyclable steel, with the main local material supplier being ArcelorMittal.

ArcelorMittal South Africa’'s continuously cast tinplate consists of single reduced cold rolled steel sheet electrolytically coated with tin. The tin coating provides corrosion resistance to the steel substrate, and plays a beneficial role with regard to the preservation of certain foods. In addition, the surface of tinplate lends itself to printing and silk screening.

Tinplate is widely used in the packaging industry for cans, can ends, larger containers and a range of closures. Tin coatings of different thicknesses are produced to suit specific requirements.

Although metal could be seen to be under threat today from cartons, pouches and plastic, BMI Research reports that the local food can market showed some volume increases, with traditional categories such as jams and fruit remaining staple products. Demand for this portion of the metal can market remained strong, despite the recession. Although much of the demand for fish is being supplied by overseas suppliers, some of those volumes are packaged in South Africa, leading to an overall increase in metal can volumes required.

Nonetheless, BMI Research estimates the food can portion of the market not to be as positive in 2010.

How cans are made

In earlier days, all cans were made of three pieces of metal (the body and two ends). Today, however, two-piece cans (the lid and the can body) provide a method for easy forming, without generating cracks.

The body is first stamped out into a cup shape from a long roll of metal and then these cups are ‘rammed’ through a series of tungsten carbide rings or decreasing diameter in a wall-ironing machine. The base is ‘domed’ and the can top trimmed before the graphics are printed on to the formed cylindrical can.

Modern double seams provide an airtight seal to the tin can, making its contents impervious to contamination by creating two tight, continuous folds between the can’s cylindrical body and the lids.

Coatings not only protect the can from the product, but attract the consumer eye on-shelf. There are external and internal lacquers.

Internal protective coatings can withstand can/component manufacturing and minimise interaction between product and the can substrate, protecting the packed product from deterioration through interaction with the substrate metal. Epoxy-based internal coatings have been used in food and beverage products for decades because of their workability, substrate adhesion, product resistance and freedom from taint qualities.

External coatings can be protective and decorative – their formulations can contain low levels of additives to enhance substrate wetting, flow, gloss and lubricity.

Can you see the future?

Globally, the can continues to evolve, with a raft of innovations that include easier-opening options. Impress has brought out Easy Peel ends for retorted foods, targeting a wide range of food applications. The company has also launched a range of microwaveable cans, in the shape of a plate, designed for ready-meals and said to be completely safe for microwave use.

The can continues its metamorphosis with numerous innovations – just one from Impress is the plate-shaped, microwaveable can.

In terms of can design, partial aperture openings have been developed for liquid products such as evaporated milk and retortable products technology is being applied to a range of food products on different can shapes and sizes.

No longer a preserve of the rich, today virtually any food can be found in a can and remains a must-have in any pantry!

‘"We currently supply around a billion cans in a multitude of sizes, diameters and various types of ends to the South African and international food markets each year, with a form of packaging that has been around for centuries and is here to stay,"’ is Johan Visser’s conclusion.

First published in PACKAGiNG & Print Media, July 2010