Food-processing waste becomes a new source of biodegradable packaging material

Researchers have developed biodegradable films by combining starch extracted from mango kernels with eggshell powder, creating a composite material with potential applications in sustainable packaging.

The study, published in Scientific Reports, explores how two food-processing residues can be converted into a functional material while addressing some of the limitations commonly associated with starch-based films.

Starch is renewable, inexpensive and capable of forming films, but materials based solely on starch can lack the mechanical strength, flexibility and moisture resistance required for practical packaging applications.

Eggshell powder reinforces the starch structure

The researchers used mango kernel starch as the main polymeric component and introduced eggshell powder as a mineral reinforcement.

Glycerol was also incorporated as a plasticiser to improve flexibility, while different processing temperatures and material concentrations were tested to determine how the formulation affected the final film.

The team used response surface methodology to study the interaction between glycerol concentration, eggshell content and gelatinisation temperature rather than relying solely on trial-and-error formulation.

Optimised film combines strength and flexibility

The preferred formulation contained 28.39% glycerol, 6.77% eggshell powder and a gelatinisation temperature of 80°C.

Under these conditions, the film achieved a tensile strength of 8.03 MPa and an elongation at break of 36.25%, combining useful mechanical resistance with significant flexibility.

The material had a measured moisture content of 7.06%, an important parameter because starch-based films naturally interact strongly with water.

Material also retains degradation potential

The researchers tested whether adding mineral reinforcement would prevent the composite from breaking down after disposal.

During a controlled 28-day soil-burial test, the selected formulation lost 36.43% of its mass.

Higher concentrations of eggshell powder generally slowed degradation, indicating a trade-off between mechanical reinforcement and end-of-life performance.

The researchers stress that these results are specific to controlled soil-burial conditions and should not be interpreted as evidence of equivalent degradation in industrial composting, marine environments or natural soils.

Waste streams provide both polymer and reinforcement

The approach is particularly interesting because both major components originate from food-processing residues.

Mango kernels contain substantial amounts of starch that can otherwise remain underutilised, while eggshells are generated in large quantities by the food industry and contain calcium-based mineral material suitable for reinforcement.

Combining the two waste streams creates a material platform that potentially adds value to residues while reducing dependence on fossil-derived polymers.

Thermal stability improves with eggshell incorporation

Analytical testing showed that eggshell powder also changes the thermal behaviour of the starch matrix.

Thermogravimetric analysis indicated improved thermal stability after incorporation of the mineral component, while infrared spectroscopy identified interactions between the different components of the composite.

These results suggest that the eggshell powder is not simply acting as an inert filler but is influencing the structure and behaviour of the biodegradable film.

Packaging applications still require further testing

The research remains at laboratory scale, and several steps are needed before the material could be considered for commercial food packaging.

Future work will need to examine film production at larger scale, food-contact safety, migration, shelf-life performance, moisture and oxygen barriers, mechanical stability during transport and degradation under realistic end-of-life conditions.

Economic and life-cycle assessments will also be necessary to determine whether collecting and processing mango kernels and eggshells provides a meaningful environmental advantage over existing biodegradable polymers.

Agro-industrial residues could support new packaging materials

The study demonstrates how food waste streams can become functional inputs for new packaging materials rather than being treated solely as disposal problems.

While the technology is not yet ready to replace conventional packaging, the combination of renewable starch, mineral waste and controlled material engineering provides another route towards biodegradable films.

The next challenge will be translating the laboratory results into films capable of meeting the demanding barrier, safety and processing requirements of real packaging applications.