You’re not alone. This little blue superfood is known for perishing quickly.
But now, a team of chemical engineers from UNSW Sydney are working on slowing down that decline. They have developed an edible film made from coffee waste that could help preserve the freshness of delicate fruits like blueberries by reducing how much water seeps in or out.
The new formulation was created and tested in their lab, making sure it could be applied directly to food. The next step is to test this as a coating in real-life environments, before scaling it up to commercial production.
“We’ve created a polysaccharide-based coating to improve the fruit’s water-vapour barrier,” UNSW lead author and PhD candidate Lilah Saidi said.
“The coating contains cellulose nanofibres (CNFs) — derived from used coffee grounds — and grapeseed oil.”
Current polysaccharide films made from other plant cellulose fibres or starches are already widely studied for use as edible coatings because they are biocompatible, biodegradable and food safe. But they are not effective at protecting fresh produce from moisture.
“Polysaccharides are excellent biopolymers for films, but their major disadvantage is their high-water affinity,” Lilah said.
“Our innovation lies in repurposing spent coffee grounds. These are an abundant waste product from cafés that can serve as both nano-fillers and stabilisers in the coating.”
Lilah said nanofibres from the coffee grounds helped create a tighter, more interconnected network, making it harder for water molecules to migrate through. The grapeseed oil, being water-repellent, further reduced the film’s affinity for moisture.
“This leads to a food film that is still clear and see-through while also having an improved mechanical strength. The nanofibres from coffee grounds make it tougher and more flexible — and are also safe to eat.”
A sustainable twist
By upcycling spent coffee grounds from UNSW’s Maze Café, the research offers a two-for-one environmental win: reducing food-industry waste while creating a biodegradable product.
Preliminary tests also suggest the oil-containing films could help inhibit bacterial growth on the film’s surface. This opens the door to a further antimicrobial function.
Soft fruits such as blueberries are more easily damaged during storage and transport because of moisture loss, microbial spoilage and mechanical damage. These all lead to food waste.
Lilah said the new formulation provided a gentle, edible ‘skin’ in the form of a spray coating or a packaging film that preserves freshness, reducing the reliance on synthetic plastics.
“These properties are especially well-suited to barrier coatings, potentially slowing dehydration, or moisture absorption, in those more highly perishable fruits like blueberries,” she said.
Challenges ahead
Lilah’s PhD supervisor Professor Cordelia Selomulya said while the research was helping improve polysaccharide-based films, turning this innovation into a solution for large-scale commercial fruit production remained a challenge.
“Translating laboratory films into a commercially viable fruit coating is no easy process,” Prof Selomulya says.
The edible coating team at UNSW includes Dr Yong Wang and Associate Professor Peter Wich. Together with Lilah and Prof Selomulya, they still need to prove the coating can be applied consistently across large volumes of fruit, ensuring it stays safe, tasteless and affordable for commercial use.
This means testing the coating on fruit beyond the lab under real-world storage and transport conditions, while exploring application methods and regulatory approvals.
“When testing this edible coating on blueberries in the lab, we also compared how they performed against uncoated blueberries when stored,” Prof Selomulya said.
“To test this in real-life environments, we first need to run a pilot trial that mimics commercial fruit processing,” she says.
“We’ve seen how this is currently done and can identify the potential steps where the coating can be applied.”
She said before the product could run at full scale, the team needed to demonstrate it worked at a small scale, to reduce risks and attract industry investment.
The team’s next study will investigate a new source of cellulose nanofibres that can be produced differently and offers further unique properties, paving the way for even more advanced and versatile coatings.
Lilah is optimistic that the new technology can not only help reduce post-harvest loss, but give coffee waste a second life.
“We’re offering a cleaner, greener way to keep fruit fresh from farm to fridge,” she said.
