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Plastics Materials Miracle of Food Packaging – and some you can eat too!
Posted on January 16th, 2017 by Dr. Sina Ebnesajjad in New Materials & Applications
Few pay much attention to food packaging when opening a bag of nutritious trail mix or potato chips. Any regard for the packaging is summarized in the reading of the nutrition facts printed on the label. More often than not indelicate words are hurled at a difficult-to-open package. The difficulty usually has to do with the thickness of the packaging. The customary question is: does it have to be so hard, so thick? Alas, if only the packaging could speak….it would tell a story. We take a look at food packaging that began to revolutionize food delivery and distribution in the late 20th century. In spite of all the food progress packaging has made, 30-40% of food is spoiled at various stages before delivery, in a world replete with hunger.
Food Packaging Requirements
Plastic food packaging, called flexible packaging, materials often start in the form of a film. The first and most important function of a package is the protection of food products. Packages protect food from the loss of nutrients, functional properties, color, aroma, taste, and preserve the general appearance expected by consumers. A good package should create an acceptable barrier between the food and external environment, particularly with respect to water vapor, oxygen, and microorganisms (which cause spoilage). Shelf life strongly depends on barrier capability of a package (Source: Plastic Films in Food Packaging, Elsevier 2013).
The second function of the package is to allow transportation of the product in a convenient manner from production (farm or factory) to retail sale and finally to consumption. A food packaging plastic must have several attributes including mechanical strength to withstand handling, transportation, storage, refrigeration and consumer handling, abrasion, and radiation resistance. Food packaging must be thermally stable to survive thermal processing such as sterilization process and in-package heating.
To meet all the above requirements packages are nearly always made of multiple plastic film layers. Those plies are laminated together using extrusion lamination or lamination alone. While any single film layer may not meet all the requirements, properly designed and fabricated laminates do. A lowly ketchup bottle may be made of a seven-layer laminate. Today, packaging technology permits shipping food products to the far corners of the world. Lives are saved in droughts, famines, wars and natural disasters thanks to plastics food packaging. But there is another side to packaging: waste disposal.
Food Packaging Consumption
Figure 1 shows the consumption volume (and future forecast) of flexible packaging between years 2010 and 2020. The majority of the consumption is in food packaging of which most are made of plastics. In 2020, some 24,000,000 metric tons of packaging will be used to pack food. The number of packages is astronomically high considering they are thin and weigh little. It is easy for post-use packaging material to become air borne because of the low weight. Consequently, used food packaging forms a large amount of scattered plastic waste on land and in the water where country size waste islands float on the oceans.
Figure 1. Forecast of consumer flexible packaging consumption by product, 2010–20 (‘000 tons)
Edible Food Packaging
Edible packaging is among a variety of solutions to waste being pursued currently. Source reduction (using less packaging) biodegradation, composting, recycling, incineration and land filling are among the other methods of food packaging disposal.
Dr. Peggy Tomasula at the U.S. Department of Agriculture (USDA) and her group have been developing an environmentally friendly film made of milk protein casein. These casein-based films are reported to be as much as 500 times better than plastics at blocking oxygen. And, because they are derived from milk, they are biodegradable, sustainable and edible. Contrary to casein, the already marketed starch packaging is more porous and allows oxygen to seep through its micro-holes. “The protein-based films are powerful oxygen blockers that help prevent food spoilage. When used in packaging, they could prevent food waste during distribution along the food chain,” Dr. Tomasula says (Source: The Daily Mail, www.dailymail.co.uk, August 24, 2016).
Researchers have been attempting for decades to make use of the excess US milk that is stored in powder form including attempts to make a film from pure casein. The efforts had failed until very recently because of water solubility. “They are proteins, which love water, and they soak up moisture in the air,” Dr. Laetitia Bonnaillie co-leader of the program said. Recently USDA scientists discovered incorporating citrus pectin in casein made the packaging stronger and more resistant to humidity and high temperatures. Plastic-based cling film dominates food wrapping. In addition to being used as plastic pouches casein can be made into cling wraps. It can also be sprayed as a coating onto food, such as cereal flakes or bars instead of a sugar coating. The spray also could line pizza or other food boxes to keep the grease from staining the packaging (Source: N. Geiling, Think Progress, https://thinkprogress.org, Aug 23, 2016).
Problems remain with casein-based packaging. Because it is moisture sensitive — and because one of the selling points is that it is edible — the packaging cannot yet be put on store shelves by itself. It would need to be used in conjunction with another, secondary layer of packaging. And while that might seem like it would create additional waste Dr. Bonnaillie said that many products already use two or more layers of packaging —the plastic bag inside a paper box, for instance. Dr. Bonnaillie also suggested that the casein-film could be used to make single-serving packaging for items like a soup or coffee, that, when dropped into hot water, would dissolve completely. The added benefit, she said, would be that the casein-film, when dissolved, would add protein to the food, making it more nutritious (Source: N. Geiling, Think Progress, https://thinkprogress.org, Aug 23, 2016).
Casein films will not be a cure all for the plastic waste problem but it has the potential to be one component of the solution. The estimated commercialization time for edible packaging is about three years. Yum!
All opinions shared in this post are the author’s own.
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Dr. Sina Ebnesajjad
President at FluoroConsultants Group, LLC