Monitoring food spoilage using smart plant-based packaging materials: Methylcellulose/soy protein films loaded with betacyanin and carbon dots

• Biopolymer-based films were fabricated from soy proteins and methylcellulose. • Betacyanin and carbon dots from flower petals ( Mirabilis jalapa ) were used as additives. • These additives exhibited strong colorimetric, fluorescent, and antibacterial properties. • The additives improved biofilm UV-blocking, wettability, tensile strength, and barrier properties. • Color changes in the biofilm indicated changes in shrimp freshness during storage. In this study, novel plant-based smart packaging materials were developed by loading betacyanin (MJ-Bs) and carbon dots (MJ-CDs) isolated from Mirabilis jalapa petals into biofilms fabricated from soy protein isolate (SPI) and methyl cellulose (MC). The MJ-Bs and MJ-CDs were used as natural color indicators and antimicrobials. Based on scanning electron microscopy analysis, these films had smooth surfaces and uniform structures. Incorporating the MJ-CDs and MJBs into the biofilms increased their UV-blocking properties (from 96.8 to 99.9 %), wettability (from 49.1 to 76.3 °), and tensile strength (from 29.3 to 36.3 MPa), and reduced their water vapor permeability (from 2.91 to 2.13 × 10 –11 g. m/m 2 . s. Pa). The color of the MJ-CD/MJB-loaded biofilms exhibited strong sensitivity to changes in pH (2 to 12), as well as to changes in ammonia vapor levels. The potential application of the biofilms was assessed by measuring their ability to monitor and preserve shrimp freshness during storage at 25 °C. The color of the biofilms shifted from pink (fresh) to brownish yellow (spoiled) during storage, indicating their efficacy for this purpose. These findings highlight the potential of these novel biofilms for quality evaluation in protein-rich fresh food products, offering significant implications for food safety, shelf-life extension, and sustainability in the packaging industry.