Best Before Never: Extending Food Shelf Life

Even before food scientists and technologists entered the industry, the extension of shelf life has been at the centre of handling foods. Traditional treatments such as canning, heating and other preserving methods with salt and sugar have been around for hundreds of years, based on the human desire to also survive lean times.

Changing consumer demands, however, have altered the treatment of foodstuff and research into better processes to extend shelf life has surged. The requirements for new technologies are precise: they should have less detrimental effects and result in no changes in the appearance, texture and flavour of the products.

"Traditional treatments have a devastating effect on the structure, taste, appearance and nutritional value of the food," says food technology consultant at the Guelph Food Technology Centre in Ontario, John Michaelides. "The new demands of consumers for fresher, natural and health delivering food products forces the industry to look at non-thermal processes, gentle processing and natural antioxidants and antimicrobials."

Gentle processing

The new credo of the industry, with consumers demanding organic, whole food products in the same breath with a guarantee for prolonged freshness, is gentle processing techniques to conserve the healthy components of food. This, however, is an enormous challenge for food scientists, as it is practically impossible to directly control the environments a product experiences once it is in the distribution channel. Therefore, researchers have to take numerous factors into account when developing new methods.

"One of the major challenges is to develop technologies that are effective and efficient," says John Michaelides. "These technologies come in the form of equipment, packaging materials or ingredients.

"Because of the multiple issues with shelf life of food products a single technology may not be sufficient to extend the shelf life of the product.

"In addition, the technologies need to be cost-effective and their application practical and economical in order to be adopted by the food industry," says Michaelides.

Microwave sterilisation

Researchers from the Washington State University in the US claim to have found the key to some of the problems with the technologies to make food that, will look, taste and be as nutritious as the original product – but with a shelf life of more than six months.

The microwave-assisted thermal sterilisation (MATS) process immerses packaged food in pressurised hot water while at the same time heating it with microwaves. Eliminating food pathogens and spoilage micro organisms in five to eight minutes, the treatment produces foodstuff with a much higher quality than conventionally processed ready-to-eat products.

Developed over a 13-year period by the university in collaboration with a number of food companies and the US Army, the technology received a second approval by the US Food and Drug Administration (FDA) in late 2010, leaving the researchers confident that the technology will soon be on the market.

"The first approval validates the scientific and engineering premises behind our work," said research leader Juming Tang in a statement in February this year.

"The second approval makes the technology viable for processing more complex food systems, which is a major milestone to commercialisation."

Tang said that the breakthrough in the development process came with the introduction of a new chemical marker system to identify a product’s cold spot and ensure that this was heated to 120°C-132°C. The team also overcame the challenge to provide proof that the product has been sterilised.

Food technology consultant, John Michaelides, believes that microwave sterilisation "seems to be a promising technology. The technology developers claim that it has been commercially applied. But I think the technology is fairly new and needs to be evaluated for many other food systems."

Edible coatings

Elsewhere, efforts in the preservation of fresh meat, which seems to be one of the biggest challenges of the food industry, are being made. Researchers from the Public University of Navarra in Spain have claimed to have developed antimicrobial edible coatings, which extend the shelf life of meat by up to 50%, to around 13 days.

Made from eight different essential oils – oregano, clove, white thyme, tea tree, coriander, sage, laurel and rosemary – the films are applied to the surface of a meat product, just like "a second skin, undetectable by consumers", according to researcher Idoya Fernández Pan. Oils from these herbs were shown to be effective against various microbial strains such as staphylococcus aureus, salmonella enteritidis, listeria innocua and pseudomona fragi.

The research focused primarily on chicken breasts and the coatings, made up of a series of antimicrobial agents, which were incorporated into the structural matrix of the product and then gradually secreted on to the surface of the meat.

"Through a bacteriostatic effect, which impedes the proliferation of bacteria, the speed of growth of the pathogen or altering agent is reduced, thus enhancing the food safety of the product and extending its shelf life," said Fernández, an agricultural engineer. According to the researchers, the outcomes of their studies have a potential direct application for the food industry, as the delaying effect on the microflora growth results in extending storage and distribution time for fresh meat products.

Food technology consultant, John Michaelides, however, warns of rash conclusions. "Although some of these oils have been well understood, their use and commercial availability may be in its infancy," he says. "The incorporation into edible films and application to the surface of food products is at the research stage and needs to be carefully evaluated before commercial acceptance."

Carbon dioxide-emitting patches

CO2 pads are seen as another promising way to extend the shelf life of food. The patches, placed inside the food packaging, to gradually emit CO2 displacing oxygen and ethylene and consequently deprive aerobic micro organisms from the ability to grow and multiply.

In February 2011, a Colorado-based company received FDA approval for a CO2 pad technology, used for meats, poultry, seafood, fruit and vegetables. According to the inventors, the pads are already used by meat plants, food processors, restaurants and wholesale businesses in the US, helping to extend the shelf life of perishable foods and to provide a high-quality product.

"Major meat processing plants in Arizona and Colorado are now using the CO2 pads in ground beef, poultry and seafood to retard bacteria growth and extend shelf life," said president of JS Food Brokers Barney Seward in an official statement. Food safety and quality would have significantly improved with the patches.

John Michaelides, however, remains sceptical and says that the patches are not foolproof. "Their use should be carefully considered as the creation of micro-aerobic or a completely anaerobic environment may create safety issues with some pathogens if other controls such as refrigeration or pH are not implemented. In addition to oxygen they displace ethylene thus slowing the ripening of fruits and vegetables. Displacement of oxygen will prevent oil oxidation as well."

The question of food safety

Along with the development of new methods to prolong shelf life, also comes the question of how these treatments influence the structure and quality of food. Old but proven technologies are continuously being replaced due to the evolution of knowledge about products as well as growing consumer demands for gentle processing. However, the new technologies can entail new dangers for the safety of food.

According to John Michaelides from the Food Technology Centre in Ontario, Canada, the question of safety for the product has to be re-asked and tested with every new technology. With strict approval processes in countries such as in the US through the FDA, the Canadian Food Inspection Agency (CFIA) in Canada and various regional organisations in Europe, the failure of such new methods has almost been barred.

Nevertheless, demands on safety are greater than ever before. Food quality has increasingly become a selling factor as consumers ask for fresher, more natural and healthy products. New technologies, to extend the shelf life of food, have to go with this trend and provide highest quality while guaranteeing a longer shelf life.