GOOD INSIDE AND OUT

A third of every kilogram of food we produce is thrown away or lost. The use of coatings and additives in packaging helps to curb the loss and waste of food

TEXTBERND KALTWASSER

It’s a staggering number: 1,500,000,000,000,000—1.5 quadrillion—kilocalories’ worth of food is wasted every year between field and fork. In purely numerical terms, that would be enough energy to feed two billion additional human beings. The worldwide economic damage that is being caused by food losses and food waste totals almost US$1 trillion per year. The careless way we deal with food is contributing to hunger and food shortages in developing countries and also accelerating land use and water consumption. If the loss of food were a country, it would occupy third place in the list of the biggest emitters of greenhouse gases.

The specific ways that foodstuffs are lost vary greatly, depending on the region of the world where the losses are happening. In the United States, an average family of four wastes food worth about US$1,500 every year. The main reason for this is that the family buys too much food and ultimately does not consume all of it. By contrast, in countries like Nigeria and Benin several hundred thousand tons of food crops rot in the fields every year because the producers cannot harvest or process it on time. The economic damage caused by these losses in sub-Saharan Africa amounts to more than US$4 billion annually.

The causes of food losses and food waste are extremely varied, and the approaches we need in order to solve these problems are equally diverse. In Africa, improved harvesting methods and expansion of the infrastructure are promising approaches, whereas in Europe and North America the greatest potential for success lies in sensitizing people to the consequences of their food purchasing behavior. Modern plastics can also make a positive contribution at every level of the food industry, ranging from food producers all the way down to the consumers.

GREENHOUSE FILMS: ADDITIVES FOR AN ­OPTIMAL CLIMATE

Greenhouse films can help food producers to ensure reliable and high-quality harvests. “These films have become an essential tool in the agricultural sector,” says Uwe Kinzlinger, an applications engineer in the Silica Business Line at Evonik. “They create an optimal indoor climate, and as a result plants can be cultivated and fresh produce can be harvested all year round.” To make sure that greenhouse films can optimally fulfill their function, manufacturers often use additives to create specific properties.

“If a small percentage of aluminum silicate is added during the manufacturing process, the film can keep heat inside more effectively. That makes it possible to maintain a higher temperature inside the greenhouse,” Kinzlinger explains. The additive does not affect the film’s transmittance, but the light is scattered and blurred to a somewhat greater extent. Depending on the climatic conditions and the location of the greenhouse, this can be a very desirable effect, because it means that sunlight is evenly distributed to every part of a plant.

If the plants in a greenhouse are exposed to strong direct sunlight, they can be damaged—especially if drops of water have gathered on the interior surface of the film in the form of dew and are concentrating the sun’s rays like a magnifying glass. If this effect raises the temperature too far, the plants are subject to sunburn and heat damage. This results in discolored leaves, rotten fruit, and the death of young plants. To prevent this from happening, the greenhouse films can incorporate additives that contain surfactants, which reduce surface tension. As a result, instead of coalescing into individual droplets, water on the inside of the covering forms into a thin film that evenly scatters the sunlight.

FILM PACKAGING: ENSURING FRESHNESS BY AVOIDING CONDENSATION WATER

The longer the production and supply chains get, the more important plastic films will become as packaging for the secure provision of food. “The debate about single-use products made of plastic is being conducted at a very emotional level. People sometimes lose sight of the fact that plastics make a crucial contribution to protecting the quality of food and prolonging its storage life,” says Pavel Belik, Head of the Compounding Product Segment in Europe, the Middle East, and Africa. For example, unpackaged meat spoils after about four days. However, if it is vacuum-sealed, it can stay fresh for as long as 30 days.

Greenhouse foils with improved features
Additives improve the properties of greenhouse films in order to ensure the optimal growth of plants

In developed regions in particular, the right packaging is an important means of reducing waste while foodstuffs are transported to supermarkets and from there to consumers’ refrigerators. The anti-fogging additives that are employed in greenhouse films can be used here as well. Variants of these additives that are authorized for direct contact with foodstuffs ensure that only small droplets of water that easily evaporate form inside the packaging. That prevents the formation of condensation water, which leads to the spoilage of the packaging’s contents. “This packaging makes the hygienic handling and transportation of many foodstuffs possible in the first place,” says Belik.

ACTIVE PACKAGING ENSURES THAT OXYGEN DOESN’T STAND A CHANCE

Traditional packaging is merely a passive covering that protects food by serving as a non-reactive or minimally reactive barrier against environmental influences. Active packaging, by contrast, creates a protective interior environment and thus keeps its contents fresh. Products such as meat and sausages, nuts, and beverages react sensitively to oxygen, which is present in residual amounts even in shrink-wrapped packages. Through the reaction with oxygen, vitamins lose their health-promoting effect and fats become rancid. Oxygen also makes it possible for bacteria and mold to grow.

As a result, many foods are now packaged in a protective atmosphere in order to keep their oxygen content low. In North America and Japan in particular, food producers use small bags full of iron compounds to further reduce the oxygen content inside packaging. However, there are limits to the effectiveness of this process: It doesn’t work for very dry products, for example. Moreover, consumers sometimes eat the contents of the little bags because they mistakenly think they contain herbs. Although other types of oxygen absorbers can protect the product, they turn an unsightly shade of yellow over time.

“We have developed a polymer-based oxygen absorber that can be directly integrated into the packaging material. It captures the remaining oxygen molecules and remains transparent,” says Pedro Vazquez Toran, who is responsible for the active packaging business at Evonik. Over the past three years this additive, which is called VISPARENT®, has passed all the stages leading to approval by the US Food and Drug Administration (FDA). Initial talks have already taken place with potential customers and processors.

THE INTERIOR COATING OF CANS: COATINGS FOR A LONG STORAGE LIFE

Along with film packaging, tin cans are among the most important types of food packaging. The high-quality sheet metal that is used for this purpose is lightweight and non-fragile, and also offers airtight protection against external influences. It enables many foodstuffs to remain edible for several years.

Metal cans are also great for recycling. Their recycling rate is over 90 percent—one of the highest in the packaging sector. The scrap metal is pressed and melted down. In the process, paints, coatings, and other additives are incinerated, while the can is turned into crude metal that can be reused in a cyclical process.

To make sure that acidic foods and other contents that could corrode the metal remain edible for a long time, the cans must be coated inside. A very thin coating prevents the can’s contents from interacting with the sheet metal and keeps metal ions from getting into the canned food. Only a small amount of the coating—between eight and ten grams per square meter—is sufficient. Depending on the size of the can, that means about three grams per can.

“What makes it challenging to formulate the coating is the way the cans are produced,” says Thorsten Brand, an applications engineer at Evonik’s Coating & Adhesive Resins Business Line. First, the coatings are applied to flat ribbons of metal or steel plates and hardened in a furnace. Only then are the coated metal sheets are turned into can bodies and can lids. “The coating has to be sufficiently flexible. Otherwise, it will tear and peel off,” says Brand. After the filling process is completed, the can is ready for the next stress test: sterilization. To lengthen the storage life of the canned food, the cans are treated in the sterilization chamber under pressure at a temperature of 130°C. Only if the coatings have also weathered this step without any damage are the cans ready for sale. High-polymer polyesters and crosslinkers ensure that the coating remains flexible but is nonetheless durable. As a result, the cans can withstand mechanical deformation as well as the subsequent hot sterilization treatment.

The food industry can only be efficient if food is kept fresh longer. Even today, the world can no longer afford to waste and lose a third of its food. This will be an even graver concern in the future. To keep around ten billion people fed in the year 2050, an additional six quadrillion kilocalories will have to be made available annually. If we succeed in cutting worldwide food wastage in half by then, part of this gap would already be closed—without putting any further strain on the soil and without limiting food consumption.

Layer by layer

It’s not apparent that high-tech materials are contained in today’s packaging. Additives (in films) and coatings (in cans) ensure the effective protection—an increased durability—of the food they contain.

Photos: Christian Lohfink/Upfront, plainpicture/Rudi Sebastian
Illustration: KNSKB+

PUBLICATION DATE

22 November 2019

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