Multifunctional layer-by-layer smart film with betalains and selenium nanoparticles for intelligent meat freshness monitoring and preservation.

Multifunctional pH-responsive films were fabricated via layer-by-layer deposition of gelatin, chitosan, and carboxymethyl cellulose (CMC), incorporating selenium nanoparticles (SeNPs) and beetroot extract (BTE), to monitor and preserve beef freshness. SeNPs were synthesized and characterized via various techniques. BTE exhibited promising functional properties, and films demonstrated a significant color transition from red to yellow across pH 2-14.