UNSW researchers are turning food waste into a protective film that could help extend the expiry date of some Australian summer fruits.
A team of chemical engineers from UNSW have developed an edible film made from coffee waste that could help preserve the freshness of fruits such as blueberries by reducing the movement of water.
The formulation was created and tested in their lab to ensure it could be applied directly to food. The next step is testing it as a coating in real environments before exploring commercial scale-up.
“We have created a polysaccharide based coating to improve the fruit’s water vapour barrier,” said UNSW lead author and PhD candidate Lilah Saidi.
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 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,” said Saidi.
“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.”
According to her, nanofibres from the coffee grounds form a tighter and interconnected network that makes it harder for water molecules to pass through. The grapeseed oil further reduces the film’s affinity for moisture. This leads to a food film that is still clear while also having an improved mechanical strength. It is also safe to eat.
Soft fruits such as blueberries are easily damaged in storage and transport because of moisture loss, microbial spoilage and mechanical damage, contributing to food waste. By upcycling spent coffee grounds from UNSW’s Maze Café, the research aims to reduce waste while creating a biodegradable product.
“These properties are especially well suited to barrier coatings, potentially slowing dehydration or moisture absorption in those more highly perishable fruits like blueberries.”
“We are offering a cleaner, greener way to keep fruit fresh from farm to fridge,” Saidi says.
However, turning this innovation into a solution for large scale fruit production remains a challenge.
The edible coating team at UNSW includes Dr Yong Wang and Associate Professor Peter Wich. Together with Saidi and her PhD supervisor Professor Cordelia Selomulya, they must still show that the coating can be applied consistently across large volumes of fruit and remain safe, tasteless and cost effective.
“Extracting nanofibres from coffee grounds is currently labour and energy intensive,” Saidi says.
“But we have shown that non oxidised CNFs from spent coffee grounds can stabilise lipophilic droplets and reinforce the film very efficiently.
“We are offering a cleaner, greener way to keep fruit fresh from farm to fridge.”