esearchers from Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora” and the Instituto de Ciencia de los Materiales de Sevilla have collaborated on an international project to develop a sustainable alternative for coating the inner surface of metal food packaging. The team has successfully created tomato pomace-based lacquers that offer a biodegradable and environmentally friendly solution to replace the petroleum-derived plastic resin currently used in food and beverage cans.
Metal cans and containers, predominantly made from steel and aluminum, are widely used in the food industry. However, when these materials come into contact with food, they can corrode and contaminate the contents. To prevent this, the inner surfaces of cans are coated with an epoxy resin, which contains bisphenol A (BPA), an industrial chemical that poses health risks when it leaches into food. BPA is known to disrupt the endocrine system and has been associated with health issues such as cancer, diabetes, and growth problems in infants and adolescents.
In response to the ban on BPA for food packaging in Spain, the research team sought an alternative solution. They turned to tomato pomace, the by-product obtained from processing tomatoes to make products such as sauces, soups, and juices. Tomato pomace, which consists of seeds, skins, and small stalks, is currently disposed of as solid waste, either by burning or using it as low-value animal feed.
In their study published in the Journal of Cleaner Production, the researchers presented their findings on “Bio-based lacquers from industrially processed tomato pomace for sustainable metal food packaging.” The tomato pomace resin they developed demonstrates several desirable characteristics, including water repellency, strong adhesion to metal surfaces, and anti-corrosive properties against salt and other liquids. The resin was subjected to rigorous testing with simulated food, and the next step will involve evaluating its performance with real food in cans and assessing its potential for industrial applications.
The use of tomato pomace as a raw material for the lacquer offers a circular bioeconomy approach by repurposing waste into valuable resources. This eco-friendly resin not only minimizes waste generation but also reduces reliance on fossil resources for manufacturing food containers, thereby significantly reducing the environmental impact associated with their production.
To obtain the resin, the researchers dried tomato pomace samples and underwent a hydrolysis process to extract the vegetable fat or lipids. The fat was then mixed with a small amount of ethanol and dispersed in a mixture of water and ethanol. This solution was sprayed onto the metal substrate to create a protective coating. Applying heat caused the molecules to bind and form the resin.
Aside from its technical properties, the tomato pomace resin demonstrates superior environmental performance compared to BPA resin. A life cycle analysis conducted by the researchers revealed that the production of tomato pomace resin generates less carbon dioxide emissions than its BPA counterpart. Furthermore, burning tomato pomace as waste contributes to higher pollution levels compared to its reuse as a resin.
The research team also assessed the resin’s impact on human health, finding that it poses lower risks compared to BPA resin in everyday products. The potential for human exposure to harmful substances through the use of tomato pomace resin was deemed minimal.
Following successful tests with simulated food, the researchers plan to move forward with trials involving real food to evaluate the resin’s performance under realistic conditions. Tomato-based products such as tomato sauce and canned tuna will be sterilized, packed in cans coated with the tomato pomace resin, and monitored for compatibility with the lacquer.
The development of tomato pomace-based lacquers for metal food packaging represents a significant advancement toward a more sustainable and safer solution for preserving food. By harnessing the circular bioeconomy potential of tomato waste, these researchers have paved the way for a greener and healthier future in the food packaging industry.
