Biodegradable but Durable: The Quest to Improve Biopolymer Packaging Materials

Researchers at Technological University Dublin have reviewed innovative methods to enhance the hydrophobicity of biopolymers, making them viable eco-friendly alternatives to plastic food packaging. Their work highlights surface engineering and food-safe additives as key strategies for improving durability, moisture resistance, and shelf life.

At the Centre for Sustainable Packaging & Bioproducts (CSPB) and the Sustainability and Health Research Hub (SHRH) at Technological University Dublin, scientists are pioneering new ways to reduce the world’s reliance on single-use plastics. In a comprehensive review published in Food Packaging and Shelf Life, researchers Sneha Sabu Mathew, Amit K. Jaiswal, and Swarna Jaiswal explore how modifying the water-interaction properties of biopolymers natural materials derived from renewable sources can lead to a sustainable transformation in food packaging. Their focus? Enhancing the hydrophobicity, or water-repelling ability, of these biodegradable materials to match the performance of petroleum-based plastics without the environmental baggage.

Why Hydrophobicity Matters in Food Packaging

While biopolymers like starch, cellulose, and proteins offer eco-friendly alternatives to plastic due to their biodegradability and non-toxicity, they come with one major drawback: they absorb water. This makes them prone to degradation, weak barrier performance, and loss of mechanical strength qualities that make them unsuitable for food storage, especially in moist environments. The review emphasizes that modifying these materials to repel water (i.e., make them hydrophobic) is essential to unlock their full potential as packaging films.

Hydrophobic packaging not only prevents food spoilage caused by moisture but also protects against oxygen penetration, extending shelf life. Films that resist water can better preserve texture, flavor, and nutritional value, making them ideal for packaging perishable goods like fruits, vegetables, meat, and dairy products.

Nature-Inspired Surface Engineering

One of the key strategies the researchers detail involves mimicking nature specifically, the water-shedding surfaces of lotus leaves. Using advanced techniques like electrospinning, cold plasma treatment, and high-pressure processing, scientists can create micro- and nano-textures on the surfaces of biopolymer films. These textures trap air pockets, reduce surface energy, and cause water droplets to roll off, much like they do on a lotus leaf or butterfly wing.

Electrospinning, for instance, creates ultra-fine fibers that make the film surface rough and hydrophobic. Cold plasma, a non-thermal ionized gas treatment, modifies surface chemistry by introducing reactive oxygen species that reorganize molecules and increase water resistance. High-pressure processing changes the internal structure of starches and proteins, helping films maintain compactness and reduce water solubility. These methods, often combined, help tailor biopolymer surfaces for superior moisture resistance without compromising biodegradability.

The Power of Food-Safe Additives

In addition to surface modifications, the review explores how integrating food-grade additives can dramatically improve hydrophobicity. Natural waxes like carnauba, beeswax, and soy wax form moisture-resistant coatings on films. Essential oils such as ginger, oregano, and lavender not only add hydrophobic properties but also deliver antimicrobial and antioxidant benefits, protecting food from spoilage.

Fatty acids including myristic, stearic, and oleic acid are another group of promising agents. These long-chain compounds interact with biopolymers to block moisture ingress and enhance film strength. Proteins like zein from corn and plant-derived polyphenols further contribute to the development of water-resistant, mechanically stable films. Some formulations, such as cellulose films treated with myristic acid, reached water contact angles above 130°, indicating excellent water repellency.

Nanoparticles, though controversial due to potential food safety concerns, are also shown to enhance film integrity. When responsibly used, they reduce porosity, increase barrier properties, and fill micro-gaps within polymer matrices, further boosting hydrophobic behavior.

Smart and Active: The New Packaging Frontier

Hydrophobically modified biopolymers are not just passive wrappers they’re becoming intelligent tools. Active packaging releases antimicrobial or antioxidant compounds to extend shelf life, while intelligent packaging detects spoilage through visual signals like color change. These innovations are particularly vulnerable to leaching and instability unless reinforced with hydrophobic modifications.

For example, films embedded with lavender essential oil and pH-sensitive pigments have shown the ability to change color in response to spoilage gases while maintaining structural integrity in moist environments. Similarly, chitosan-cellulose nanocomposite films treated with zinc oxide nanoparticles significantly extended the shelf life of black grapes, outperforming polyethylene packaging in moisture and oxygen resistance.

Challenges and the Road Ahead

Despite promising results, hydrophobically modified biopolymers must overcome challenges before large-scale adoption. Consumer perception, regulatory restrictions, and manufacturing costs remain hurdles. The European Union’s food contact regulations (Regulation EC No. 1935/2004 and 450/2009) demand strict evaluation of material safety, especially for active and intelligent packaging components. Preventing additive migration into food is key to ensuring safety and consumer confidence.

Still, the researchers are optimistic. They highlight future directions such as using agricultural waste as hydrophobic agents, integrating humidity-responsive sensors, and refining scalable coating techniques. The goal is to create packaging that is not only compostable and safe but also functional, protective, and responsive.

The review from Technological University Dublin sets a solid scientific foundation for packaging innovation that aligns with global sustainability goals. By advancing biopolymer hydrophobicity, the researchers are helping the food industry take a crucial step away from plastic dependency and toward a circular, nature-inspired future one that keeps food fresher, consumers safer, and the planet cleaner.