Improving food packaging, October 2022

October 2022

• For decades, the world has benefitted from plastic, but the material is difficult to recycle and has been building in the environment since its invention.
• More research indicates that plasticizers and PFAS have detrimental health effects when used in proximity to food where they leach in an contaminant the products.
• Investment in bioplastics in on the rise, but some are concerned that these materials represent yet another demand on agricultural land already slotted for food and biofuel production.

For all the concern consumers have over the food they eat, new research indicates they also have cause to worry about its containers. Plasticizers are “ending up in our food, in our bodies, and are leading to serious and irreversible health effects,” said Ami Zota, an associate professor at the George Washington University’s Milken Institute School of Public Health in Washinton, DC (https://tinyurl.com/44ac5bk7).

Ortho-phthalates, often referred to as “phthalates,” are chemicals used in plastic products like food packaging or other minor food contact uses such as components of adhesives, lubricants, and sealants. 

In July, the Journal of the American Medical Association Pediatrics published an analysis of National Institute of Health data from more than 6000 pregnant women in the United States. The results showed that women with a high level of phthalate metabolites in their urine were as much as 16 percent more likely to experience preterm labor (http://doi.org/10.1001/jamapediatrics.2022.2252).

Plastic packaging maintains the safety and quality of our food, but the material has contributed to concerns about human health and the environment for decades. Researchers are eager to develop packaging that inhibits microbial contamination and lipid oxidation while also coming from a natural source that decomposes quickly when turned into waste.

So far, commercial bioplastic frontrunners include polylactic acid (PLA) and polyhydroxyalkanoates (PHA)—a class of compounds belonging to the polyhydroxyester family of 3-, 4-, 5- and 6-hydroxy alkanoic acids. These materials are made from the microbial fermentation of corn, sugar, or vegetable oils. Scientists are also testing packaging films made out of milled flours from a variety of crops.

 “The food industry should consider implementing biopolymer packages as a natural

and environmental-friendly alternative to prolong the shelf life of sensitive foods,” said Cecilia Gabriela Riveros, of the National University of Cordoba, Argentina, and lead author of a paper on peanut flour biopackaging.

Biopackaging will need to withstand the fluctuation of ambient conditions encountered between product manufacture and product sale. The material must also protect a product for water and oxygen, while remaining inert and not leeching into food. Moreover, when the time is right, biopackaging should decompose quickly without a trace.

Whether new types of biopolymers are capable of the heavy-lifting of their synthetic counterparts remains a question. Researchers are testing natural materials in hopes of finding something that satisfies most of the requirements on the packaging checklist.

Half a century of plastic packaging accumulating in the environment is taking a toll. New biopackaging materials cannot be discovered too soon.

FIG. 1. In 1950 the world produced 2 million tons of plastic per year. Since then, annual production has increase nearly 200-fold, reaching 381 tons in 2015—equivalent to the mass of two-thirds of the world population. Source:ourworldindata.org.

Buried in plastic

“Worldwide, at least 8.8 million metric tons of plastic waste enter the world’s oceans each year — the equivalent of dumping a garbage truck of plastic into the sea every minute,” says a recent report by the US National Academy of Sciences (https://tinyurl.com/2p9y3eae). 

In 2014, researchers used drones to calculate the size of the Great Pacific Garbage Patch, discovered in 1997. They found that in just under 20 years, the vortex of floating plastic waste had grown 100 times bigger.

The United Nations Environmental Program states that we produce about 400 million tons of plastic waste every year. They indicate that since the 1970s, the rate of plastic production has grown faster than that of any other material. And they say, if historic growth trends continue, global production of primary plastic is forecasted to reach 1,100 million tons by 2050 (https://www.unep.org/interactives/beat-plastic-pollution/).

Roughly 45 percent of plastic produced goes into packaging which consumers frequently disposed of after a single use (https://ourworldindata.org/plastic-pollution). This is a problem since petroleum-based plastics do not decompose. They simply become smaller, microplastic. In fact, only 9 percent of all plastic every created has been broken down and recycled (https://tinyurl.com/mryyrae6).

FIG. 2. Packaging was the dominant use of primary plastics. Source:ourworldindata.org.

The inundation of plastic in our lives has resulted in the presence of plastic in our bodies. The microplastic in the ocean consumed by fish progress up the food chain eventually ending up on our dinner plates. Based on the amount of plastic in staple foods, researchers at the University of Newcastle in Australia estimate, that people ingest five grams of plastic each week, about the amount in a credit card (https://tinyurl.com/2p9ejk6b).

Research out of France this summer determined that 78 percent of bottled water produced there contains microplastics. And several studies have confirmed the presence of microplastics in human blood (https://doi.org/10.1016/j.envint.2022.107199).

Of course, plastic presents problems before becoming waste. Plasticizers and protective coatings leech from packaging into food.

“The FDA is aware of concerns raised about possible health effects of exposure to high levels of phthalates,” says the US Food and Drug Administration website. “However, at present the FDA is not aware of evidence that the dietary exposure to phthalates resulting from their use as food contact substances poses a safety risk.”

The FDA currently allows nine phthalates in food contact applications (eight for use as plasticizers and one for use as a monomer). Earlier this year three separate petitions were filed with the FDA requesting they revoke authorization of phthalates for food contact use. In May, the FDA rejected these petitions.

In July, they reopened “the comment period in response to a request to provide stakeholders with more time to fully consider the request for information and submit comments.” The deadline for this new comment period has not yet been announced.

The push for tighter regulations on phthalates coincides with growing US legislation at the state level to ban per- and polyfluoroalkyl substances (PFAS) from food packaging. Recent studies found that the grease-resistant packaging at prominent fast food chains contained over 100 parts per million fluorine from PFAS.

In 2020, the FDA initiated a three-year, voluntary program to phase-out PFAS. The agency is currently reviewing a petition from environmental groups calling for a PFAS ban in food packaging (https://tinyurl.com/yywkf2v7). The European Union, Denmark, and Canada have opted for a total ban of PFAS on all uses of the substances.

With so many negative aspects of plastic use in food packaging, it is no surprise that more investors are paying attention to bioplastics.

Growing investment in biopolymers

According to data from the market intelligence platform, i3 Connect, in 2022 corporations and venture capitalists invested $500 million in bioplastics manufacturing. Last year, investment peaked at $350 million. The bioplastics market is likely to reach $29 billion in the next five years, according to Zion Market Research (https://tinyurl.com/4xdx7skm).

The first bioplastic to get traction in the market is PLA. The material, made by fermenting sugar from corn and sugar cane, usually takes the form of compostable food service items such as plastic cutlery, clear cups, wrappers, and containers.

A joint venture between Cargill, with corporate headquarters in Minneapolis, Minnesota, USA and PTT Global Chemical, based in Thailand, resulted in the formation of NatureWorks, the world’s largest producer of PLA. The company’s plant in Blair, Nebraska, USA makes 150,000 metric tons of bioplastic pellets a year.

Although PLA is a popular bioplastic, it does not easily biodegrade. Due to its aliphatic polyester composition, a hydrolysis reaction will decompose the material, but that requires excess energy. To degrade naturally, PLA can be mixed with food waste in industrial composters or buried in landfills for a few decades (https://doi.org/10.1016/j.heliyon.2021.e07918).

In comparison, experiments with PHA show it can biodegrade in six months in marine environments (depending on the water temperature) and two years in soil.

NatureWorks partnered with a South Korean company called CJ Bio that manufactures PHA. CJ Bio is expanding its plant in Indonesia and is planning to build a large plant in the Americas, said Raj Kirsch, vice president of research and development, in an interview.

A company call Danimer Scientific, with headquarters in Bainbridge, Georgia, USA, recently expanded its PHA production capabilities by opening a second plant in Winchester, Kentucky. Opening a second facility makes Danimer the world’s largest PHA producer.

The company’s CEO says they have development projects to replace any plastic product imaginable with PHA made through a fermentation process using canola oil feedstock. The market supply of PHA will soon match PLA.

Edible films

Another way to approach the plastics problem, is to make food packaging out of substances that are safe for humans to eat.  

Starch, a polysaccharide sourced from plants, has been formulated into a thermoplastic that can be remolded for use in food packaging. Unfortunately, these materials are sensitive to water absorption and do not exhibit the same level of function as plastics. When chemically modified, however, they can be blended with other biopolymers to improve their mechanical properties (https://doi.org/10.3390/polysaccharides3010007).

A research team in Argentina, led by Nelson Grosso, professor of food science and technology at the National University of Cordoba, is testing a blend of starch, protein, and lipids to evaluate their application as edible films. Since proteins, hydrolysates, and peptides contain polyphenols that act as antioxidants through free radical uptake and metal chelation, the researchers speculate that these compounds will result in the film effectively acting as a food preservative.

Among other oil seeds, one of the films the research produced was from chickpea flour. They milled the seeds and extracted the soluble sugars before film formation. The researchers stirred chickpea flour in a warmed, basic solution to dissolve the protein. Then, to plasticize the suspension, they added glycerol, let it cool and poured it into film molds. The films were smooth and transparent with a slight yellow tint. Grosso’s team stored the films for two months, periodically measuring a range of properties (https://doi.org/10.1111/1750-3841.15559).

Similar to other edible films under investigation, including blue corn flour, sesame protein and faba bean protein, they found that the films stiffened after 45 days of storage, potentially due to glycerol rearrangement. The migration of plasticizer in the film could result from a loss of moisture which coincides with the researcher’s observation that water vapor permeability decreased during the 60 day experiment.

However, the results of experiments on edible films were generally positive. The ordered hydrogen-bond network between the proteins and carbohydrates of edible films produce good oxygen and water barrier properties. By using flours that include a seed’s lipids, the team believes the hydrophobic molecules integrate into this matrix and provide an antioxidant benefit to food packaging.

 In a more recent study, the team compared storage pouches made from edible films—in this case, defatted peanut flour—with the common synthetic plastics, polyethylene and polyvinyl alcohol. They filled the pouches with sunflower seeds which are susceptible to rancidity due a high concentration of unsaturated fatty acids. The researchers found that, after 30 days, the edible film pouch protected the sunflower seeds from becoming rancid better than the pouch made from polyethylene (https://doi.org/10.1002/aocs.12562).

FIG.3(a) Defatted peanut flour films and (b) defatted peanut flour pouch with sunflower seeds. Source: Riveros et al. JAOCS, 99, 153, 2022.

The main criticism of biopackaging, it is that making the materials requires taking up arable land to grow crops that could be used to produce food. According to a 2014 study, nearly a quarter of agricultural land producing grain was used for biofuels and bioplastics (https://doi.org/10.1016/j.rser.2014.01.056). Some experts say land use change must be considered when determining whether bioplastics are better for the environment, since the fertilizers and pesticides used to grow crops could actually increase pollution.

A representative for NatureWorks calls these concerns unfounded. Their company extracts sugar from corn that is then used in other products, like ethanol, sweeteners, or cooking oil. Although, Danimer’s feedstock is canola oil, they repurpose the crush into fertilizer and livestock feed.

So far, life cycle assessments of bioplastics have found that using bioplastics can reduce greenhouse gases on both the manufacturing and waste disposal side of the product. In terms of handling the waste, studies show carbon emissions could be lowered by up to 70 percent.

Ingesting oxidized dietary lipids routinely triggers the chronic inflammation that cascades into life-threatening disease. Food packaging is critical in preventing this type of chemical reaction from occurring. However, the packaging cannot negate this benefit by creating bigger problems long-term. Scientists now realize that for the past 70 years that is exactly what plastic has done. Recent research indicates that they are close to finding solutions that could reverse the damage.