Written by: Katie Rodger, Ph.D. | Issue # 61 | 2017
- In 2016 USDA researchers developed an edible, food packaging bio-polymer from milk casein that may keep food fresher than traditional plastics.
- Casein bio-polymers can minimize waste and add nutritional value to foods.
- Casein has been historically used to make glue, paint, and textiles.
“Paper or plastic?” This simple question, asked daily at grocery stores and markets around the world, has become increasingly complex over the past couple of decades. The choice between all-natural, biodegradable fibers and synthetic, single-use films has political and environmental consequences ranging from deforestation to endangered sea turtles. But a recent innovation in the development of food packaging may signal a new option altogether. Instead of recycling or wasting your bag, what if you could eat it?
To be clear, edible shopping bags are not what we’re talking about, but at last August’s meeting of the American Chemical Society in Philadelphia, Peggy Tomasula, Laetitia Bonnaillie, and their USDA research team presented their current progress in developing milk protein-based food packaging. Because of their molecular flexibility and emulsifying and stabilizing properties—as they are mostly random coil polypeptides—caseins possess good film-forming and coating abilities . Thus there have been other attempts to produce a casein-based food film; yet earlier versions of these were not effective barriers to moisture, and therefore were not developed for widespread use. This latest iteration, however, highlighted in a video  featuring Tomasula and her team, combines milk casein with glycerol and citrus pectin to form a soft but structurally sound bio-polymer that protects food from light, oxygen, and some humidity.
Two of the most likely applications of these bio-polymers, according to Bonnaillie , are as single-serving wrappers and as dissolvable packets. String cheese and some refrigerated snack foods are often packaged in individual plastic wrappers, ideal for packed lunches. But the amount of waste for these items is disproportionate to their full-sized counterparts and is a concern. Likewise, dehydrated soup packets could be waste-free with casein film pouches replacing traditional paper or plastic packaging. Packets can be dropped into warm water and the film dissolves within seconds. In both of these instances, edible casein bio-polymers would minimize waste, and could also add nutritional value as vitamins and supplements can be added to the films during manufacturing. Many hope that this most recent advancement in developing casein-based bio-polymers will be a turning point for such edible packaging and that we soon may see them used commercially.
The same chemical properties that make casein effective in bio-polymers also enable its use in other ways. Dating as far back as the Middle Ages, records indicate that wood glues and cement-like materials were derived of casein , and many manufacturers from the nineteenth century through the present have relied on glues made of casein, sodium hydroxide, and calcium hydroxide. Though synthetic alternatives are available, certain niche industries and applications still prefer casein-based glues, including the labeling of bottles.
Another historical use for casein was as an additive to paint. Specifically because of its water solubility and ability to bind to pigments, casein-based tempera paint dates back to ancient Egypt and is still available today. Many artists have been attracted to its fast-drying properties, including Andy Warhol, who painted “Popeye” and “Dick Tracy” with it in 1960. Most contemporary artists prefer acrylic paint, which was developed in the late 1960s, though casein paint is still available and used by some.
Perhaps somewhat surprisingly, casein-based fibers and textiles were developed in the early 20th century, and their use peaked around World War 2 when they were combined with wool, cotton, and rayon. Aralac, the U.S. trade name for one such fiber, was not particularly strong, and so was often woven into fabric blends with pure wool, which was scarce during wartime, for added durability. It was also often a rather bland looking material, as it did not hold dye well. Though most have abandoned the idea of casein fibers, a German company is currently producing a milk-based fabric that has a silk-like texture .
A common feature of these casein-based non-food products—glue, paint, and fiber—is that each was superseded with a more durable, cost-effective, and/or marketable synthetic replacement. Yet with Tomasula and her team’s recent production of an improved, edible casein-based bio-polymer, perhaps this trend is shifting. As we look for safer and sustainable options for food packaging, it seems logical to turn to the staples of our diet, and their component parts, for inspiration and innovation. Hopefully, in the near future, we will be able to opt for not only paper or plastic but for milk.
1. Audic, J., Chaufer, B., Daufin. G. 2003. Non-food applications of milk components and dairy co-products: A review. Lait. 83(6): 417-38.
2. “Edible, Biodegradable Food Packaging.” https://www.youtube.com/watch?v=wt32GgQGTcI
3. Chen, H. 1995. Functional properties and applications of edible films made of milk proteins. Journal of Dairy Science. 78(11): 2563-83.
4. Qmilk. (1 April 2017). Retrieved from http://de.qmilk.eu//.