Material choice is key for food packaging
Ben Smye, head of growth at materials database Matmatch, explains what effective packaging materials are available on the market and what the future holds for the food industry.
ecause food has a limited shelf life and is prone to contamination, the first job of food packaging is to limit bacteria and maintain food freshness — from production to distribution and sale. A marketer might disagree but selling the food itself is secondary. After all, if the product does not reach the customer intact and free of ingress, its sale becomes valueless.
Understanding this does not mean that choosing the right packaging material is easy though. While the most exciting innovations in food packaging materials are in the fields of biopolymers, the most used are the obvious: glass, plastic and aluminium.
Starting with the obvious
Glass is one of the most common and oldest packaging materials. It is an inert material, due to its chemical structure and is completely amorphous with small pores, which prevents gaseous molecules from passing through it, making it ideal for storing fluids. While glass is 100% recyclable, it is also very brittle, which makes it a poor choice for rough transportation or handling.
Paper is also popular in the packaging sector. However, due to its properties and treatment, it allows additives and external contaminants to migrate through the packaging into the food. Aluminium is a good alternative because it possesses high antibacterial activity and is nearly as recyclable as glass.
The environmental credentials of aluminium are trumpeted by multiple organisations, including The Aluminium Association and the Aluminium Federation (Alfed).
Recently, researcher Dr Biao Cai, from the University of Birmingham’s School of Metallurgy and Materials, has created further possibilities for recycling the material. The process uses sophisticated high-speed X-ray imaging to record the formation of micro-crystals as alloys cool and solidify under a magnetic field.
Biao has already invented a technique to improve aluminium recycling by removing iron, which is a detrimental element that can make aluminium brittle and limit its use in premium applications such as aircraft.
“These microscopic crystals ultimately determine the physical properties of the alloy. To be able to adjust their shape, structure and direction of growth will enable us to perfect processes for both manufacturing and recycling of metals and alloys,” says Biao.
Looking to polymeric materials
Despite these advances, polymeric materials yield the most benefits in food packaging. Polymers can be either petroleum/fossil-based or bio-based.
The most common petroleum-based polymer is plastic, which accounts for around 2% of the gross domestic product of most developed countries, according to Vimal Katiyar in the recent book, ‘Sustainable Polymers for Food Packaging: An Introduction’, and more than 50% of all plastic is used in food packaging.
Plastic is inexpensive, lightweight, and chemically resistant and its transparency and printability mean it is attractive to consumers. However, it has a very low degradable capacity, making it a significant cause of pollution.
As a result, manufacturers are increasingly turning to biopolymers, made entirely out of renewable sources, such as biobased feedstocks, which use no fossil fuels. This means that they can be manufactured continuously without depleting resources, reduce CO2 emissions by up to 70%, according to Katiyar, and form part of the circular economy.
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One company developing new and innovative bioplastics is California-based Mango Materials. It uses waste gas to develop its biopolymers and its CEO, Molly Morse, explained her views to The Cleantech Group, a research organisation specialising in environmental issues recently.
“We believe biopolymers are critical to keeping our natural environment pristine. Biopolymers are no longer just a nice-to-have – now they are a need-to-have, and Polyhydroxyalkanoates (PHA) offer a solution that is completely harmonious with nature,” says Morse.
“Competing with large-scale, low-cost, polluting plastics presents a major challenge to PHA and other biopolymers. Significant production infrastructure for traditional plastics is already in place, resulting in billions of dollars of steel in the ground. Mango Materials and other biopolymer companies must scale up to increase supply and ultimately compete on price.”
Manufacturers are increasingly turning to biopolymers, made entirely out of renewable sources.
Biobased packaging materials are largely divided into three groups, based on their origin. The first, natural polymers, such as starch, cellulose, lignin, proteins or lipids, are produced from agricultural resources.
The second group, microbial polymers result from the fermentation of carbon substrate by microorganisms. These include the PHAs, such as Mango Materials’ products, which can be used for cheese coating or to make fast food plates. The third category includes bioderived monomer polymers, such as Polylactic acid, which is synthesised from lactic acid bioderived monomers.
Although the benefits of using biobased polymers are evident, their production is stalled by high production costs and limited functional properties compared to petroleum or fossil-based polymers. Nevertheless, their minimal environmental impact is a driving force.
It may well be that it is this driving force, rather than marketing techniques designed to evoke childhood memories or make you want to reach for your favourite bottle of wine, which will drive developments in packaging in the future.