Mango Kernels and Eggshells Create Flexible Biodegradable Films With Packaging Potential

By Akshatha ChandrashekarReviewed by Susha Cheriyedath, M.Sc.Sep 17 2026

Two common food-processing residues serve as the building blocks of a starch-based composite as researchers test how formulation and processing conditions affect strength, flexibility, moisture resistance, and degradation.

Paper: Mango kernel starch-based biodegradable films reinforced with eggshell powder as a sustainable plastic alternative. Image Credit: Mario Guerriero / Shutterstock

A recent study in Scientific Reports explores the development of biodegradable films from mango kernel starch (MKS) reinforced with eggshell powder as a potential sustainable alternative to conventional plastics. The researchers combine two abundant agro-industrial by-products to create a starch-based composite with improved functional properties. The findings demonstrate how waste-derived materials can support the development of biodegradable films with potential applications in sustainable packaging.

Addressing the Plastic Waste Challenge

Petroleum-based plastics offer excellent mechanical durability and processing properties, but their persistence after disposal poses a major environmental burden. Researchers have been exploring renewable and biodegradable materials that can replace conventional polymers in selected applications. Starch is gaining increasing attention as a promising film-forming material because it is abundant, inexpensive, renewable, and readily available. But starch-based films often lack the mechanical strength, flexibility, moisture resistance, and thermal stability needed for practical applications.

This study addresses these limitations by combining mango kernel starch (MKS) with eggshell powder. Mango processing generates large quantities of kernels with substantial starch, while eggshells are another readily available food-industry residue. This combination allows the researchers to tune the film's mechanical and physical properties while retaining its capacity to degrade under the tested conditions.

Engineering Mango Kernel Starch Films with Eggshell Powder

The researchers first investigated MKS production and examined how sodium metabisulfite treatment affects starch yield and its inherent properties. The highest starch yield was 72.25% at 0.15% sodium metabisulfite, compared with 56.45% in the distilled-water control. They then fabricated the films via solution casting, systematically varying three key parameters: glycerol concentration, eggshell powder loading, and gelatinization temperature.

The study examines glycerol concentrations of 0, 25, and 50% w/v, eggshell powder contents of 0, 5, and 10% w/w, and gelatinization temperatures of 70, 75, and 80 °C. These variables influence starch gelatinization, polymer chain interactions, film formation, flexibility, and the interaction between the starch matrix and the mineral filler.

The researchers use a Central Composite Design (CCD) within a response surface methodology approach to examine the combined effects of the processing parameters. The statistical models examine how the processing variables affect moisture content, tensile strength, elongation at break, and degradation. The significance of individual factors and interactions varied across the measured responses.

This approach provides a systematic route to managing several competing properties. Glycerol concentration influences the film’s flexibility, moisture content, and mechanical strength, while moderate eggshell powder loading can reinforce the starch matrix; higher concentrations can reduce strength as particles agglomerate and create weak points. Adjusting these variables helps achieve a useful combination of mechanical and physical properties.

Material Composition Shapes Film Performance

The multi-response analysis identifies 28.39% glycerol, 6.77% eggshell powder, and a gelatinization temperature of 80 °C as the preferred formulation. Under these conditions, the composite film reaches a tensile strength of 8.03 MPa and an elongation at break of 36.25%. These results indicate that the selected material combines useful strength with considerable flexibility, two properties that strongly influence the practical performance of biodegradable films.

The film has a moisture content of 7.06%, an important characteristic for starch-based materials, which are hydrophilic and sensitive to water. Moisture uptake can affect dimensional stability, flexibility, strength, and storage behavior. The researchers adjust the formulation to account for interactions among starch, glycerol, and eggshell-derived mineral components while maintaining acceptable film characteristics.

The researchers also evaluate degradation to determine whether the composite continues to break down after incorporating mineral reinforcement. The selected film lost 36.43% of its mass during a 28-day controlled soil-burial test. Increasing eggshell content generally slowed degradation, so the preferred 6.77% loading represented a compromise between mechanical reinforcement and maintaining an acceptable degradation rate under the tested conditions. The authors caution that this rate is specific to laboratory soil-burial conditions and cannot be directly extrapolated to field composting or to marine or freshwater environments.

Fourier-transform infrared spectroscopy (FTIR) reveals changes in the film’s chemical environment following eggshell incorporation, indicating interactions between the composite components. Thermogravimetric analysis (TGA) also shows improved thermal stability. Together, these results indicate that eggshell powder modifies the structure and thermal response of the starch matrix rather than simply occupying space within the film.

Advancing Waste-Derived Materials for Sustainable Packaging

The study demonstrates how two food-processing residues can combine to create a higher-value biodegradable material. MKS forms the polymeric foundation, glycerol provides flexibility, and eggshell powder contributes reinforcement and improved thermal stability. The preferred formulation combines mechanical performance, flexibility, moisture content, and degradation under the tested conditions.

The work also highlights the importance of formulation and processing conditions in determining biopolymer performance. The performance of starch films depends strongly on plasticizer concentration, filler content, thermal treatment, and interactions among their constituent phases. The response surface methodology used in this study provides a practical way to identify suitable combinations of these variables while reducing the need for extensive trial-and-error experimentation.

The study also illustrates how agricultural and food-processing residues can be incorporated into higher-value material applications, supporting broader circular-material strategies. The findings further indicate that eggshell powder can actively modify the composite’s chemical environment and thermal behavior.

Future research should examine production scale-up, longer-term degradation in different environments, food-contact safety and migration, practical food applications, and economic and life-cycle performance. Addressing these gaps will help determine whether the laboratory-scale films can progress toward commercially and environmentally viable packaging applications.

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