Houston researchers find new eco-friendly way to preserve produce
Hunger impacts over 800 million people worldwide, leaving nearly 10 percent of the population suffering from chronic undernourishment. The distressing reality of food shortages co-exists in a world where 1.3 billion tons of food — nearly a third of what's produced — is wasted each year, according to the Food and Agriculture Organization of the United Nations. Rice University's scientific research team's latest discovery takes a crack at ending food shortages and improving sustainability with a common kitchen necessity: eggs.
The discovery of egg-based coating is promising to researchers, as it manages to both prolong produce shelf-life by double while impacting the environment.
"We are reducing the cost, and at the same time we are reducing the waste," says Muhammad M. Rahman, a research scientist at Rice University. "One in every eight people are hungry...on the other side, 33 percent of food is wasted."
It's no secret that overflowing landfills contribute to the climate crisis, piling high with food waste each year. While the United States produces more than seven billion eggs a year, manufacturers reject 3 percent of them. The Rice University researchers estimate that more than 200 million eggs end up in U.S. landfills annually.
According to the Environmental Protection Agency, half of all landfill gas is methane, a hazardous greenhouse gas that contributes to detrimental climate change. Landfills are the third-largest contributor to methane emissions in the country, riding the coattails of agriculture and the energy industry.
COVID-19 has upended supply chains across the nation, and in recent months food waste has become an even more pressing issue. The disruptions of consumer purchasing habits and the indefinite closures of theme parks and select restaurants put a burden on farmers who planned for larger harvests and restaurants unsure of how to adjust. With more Americans cooking at home, panic-buying from grocery stores is also playing a role in accumulating waste.
To understand the challenges of the food industry, it's important to acknowledge the biggest menace to the supply chain: perishability. Fruits and vegetables only last a few days once arriving in grocery stores due to culprits like dehydration, texture deterioration, respiration and microbial growth. Rice University researchers sought to create a coating that addresses each of these issues in a natural, cost-effective way.
Brown School of Engineering materials scientist, Pulickei Ajayan, and his colleagues, were looking for a protein to fight issues like food waste. Rahman, a researcher in Ajayan's lab, received his Ph.D. from Cornell University studying the structure-property relationship in green nanocomposites. He and his fellow researchers found that egg whites were a suitable protein that wouldn't alter the biological and physiological properties of fruit. The study published in Advanced Materials took one year and three months to complete.
According to Rahman, the egg-based coating is non-toxic, biodegradable and healthier than other alternatives on the market. Wax is one common method of fruit preservation that can result in adverse effects on gut cells and the body over time.
"Long-term consumption of wax is not actually good and is very bad for your health," says Dr. Rahman. After wax is consumed, gut cells fragment the preservatives in wax to ions. This process can have a negative impact on "membrane disruption, essential metabolite inhibition, energy drainage to restore homeostasis, and reductions in body-weight gain," according to the research abstract.
Preservation efforts like wax, modified atmospheric packaging and paraffin-based active coatings are not only more expensive and less healthy, but they also alter the taste and look of fruits.
"Reducing food shortages in ways that don't involve genetic modification, inedible coatings or chemical additives is important for sustainable living," Ajayan states in a press release.
The magic of preservation is all in the ingredients. Rice University's edible coating is mostly made from household items. Seventy percent of the egg coating is made from egg whites and yolk. Cellulose nanocrystals, a biopolymer from wood, are mixed with the egg to create a gas barrier and keep the produce from shriveling. To add elasticity to the brittle poly-albumen (egg), glycerol helps make the coating flexible. Finally, curcumin—an extract found in turmeric—works as an antibacterial to reduce the microbial growth and preserve the fruit's freshness.
The experiment was done by dipping strawberries, avocados, papayas and bananas in the multifunctional coating and comparing them with uncoated fruits. Observation during the decaying process showed that the coated fruits had about double the shelf-life of their non-coated counterparts.
For people with egg allergies, the coating can be removed simply by rinsing the produce in water. Rice University researchers are also beginning to test plant-based proteins for vegan consumers.
For its first iteration, Rahman finds that the coating shows "optimistic results" and "potential" for the future of food preservation.
"These are already very green materials. In the next phase, we are trying to optimize this coating and extend the samples from fruits to vegetables and eggs," says Rahman.
Researchers will also work to test a spray protein, making it easier for both commercial providers as well as consumers looking for an at-home coating option. From a lab in Rice University to a potential shelf life in stores, the innovation of food coating is just beginning.