Preparation and characterization of nanobiocomposite films from sodium caseinate, halloysite nanoclay, and geraniol and application on capsicum (Capsicum annuum) fruits as a case study

Abstract

Plastics are advantageous in food packaging due to their mechanical strength, flexibility, and low-cost nature. However, their prolonged degradation is not environmentally friendly. Therefore, there is a need to develop alternative food packaging systems. To this end, nature-derived materials such as milk proteins provide a viable solution. In this study, sodium caseinate (SC) based nanobiocomposite films were developed with the incorporation of halloysite nanoclay (HS) and geraniol essential oil (GR). The films exhibited reduced moisture content (from 13.47% ± 0.84%–7.85% ± 0.72%), water solubility (from 20.55% ± 0.80%–9.47% ± 1.06%), water vapor transmission rate (from 84.50 ± 8.06 to 37.33 ± 6.46 g h−1m−2) and increased surface hydrophobicity (contact angle from 53.27 ± 2.97 to 82.70 ± 1.42°) compared to pure SC films. The films were uniform with a semi-crystalline microstructure and an increase in the β-sheet to α-helix ratio was observed due to the increase in the loading concentration of HS and GR. Adding HS and GR improved the mechanical properties, and Young's modulus increased from 69.85 ± 6.12 to 110.12 ± 6.99 MPa. The films demonstrated potent antimicrobial efficacy against Gram-positive Bacillus cereus and Gram-negative Escherichia coli. The SC/HS/GR dispersions could extend the shelf-life of capsicum fruits by reducing weight loss and color change and maintaining firmness. Overall, this research highlights the potential of milk protein-based films incorporated with halloysite and geraniol as sustainable and effective solutions for active food packaging applications.