Development of a Novel Film Based on Casein/Modified Tragacanth Gum Enriched by Carbon Quantum Dots for Shelf-Life Extension of Butter

Casein proteins were cross-linked with dialdehyde tragacanth gum (DTG) to create a film with improved physico-mechanical properties. The DTG/casein film with a 2:1 ratio exhibited good physical and barrier properties, such as tensile strength (TS) (12.92 MPa), water contact angle (WCA) (73.2 & DEG;), water vapor permeability (WVP) (2.1 x 10 - 10 g & BULL;mm/h & BULL;mm(2)& BULL;Pa), and water solubility (WS) (22.3%). Carbon dot (CD) nanoparticles were synthesized from milk permeate using a hydrothermal method. CDs (5 to 50% w/w) were incorporated into the optimal cross-linked casein films to create casein-based nanocomposites. Adding CDs (up to 15% w/w) increased the film's tensile strength by 36%. Scanning electron microscopy (SEM) confirmed the homogeneous distribution of 5% CD in the films without aggregation. The hydrophilicity of the films increased with the addition of CDs. Additionally, incorporating CDs significantly reduced UV transmission, with a 99.09% reduction in UV-C and a 97.46% reduction in UV-A. The CD-added nanocomposite films demonstrated potent antioxidant activity, increasing DPPH scavenging from 18.1 to 94% and ABTS scavenging from 16.4 to 89.3%. No cytotoxicity was observed in normal cells (HUVEC) even after 72 h of exposure. Coating butter products with the composite films for 60 days resulted in decreased peroxide value (PV) and thiobarbituric acid reactive substances (TBARS), indicating an oxidation-reduction process. These findings highlight the potential of cross-linked casein films with CDs to extend the shelf life of food products in the food industry.