Indicator Films Containing Dendrobium Orchid Flower Extract and TiO2 Nanoparticles for Monitoring Fish Fillet Spoilage

This work aimed to study a novel pH indicator film prepared from carboxymethyl cellulose (CMC)/tapioca starch (TS) incorporating Dendrobium orchid flowers and TiO2 nanoparticles for monitoring fish fillet freshness. The films were prepared based on carboxymethyl cellulose (CMC) and tapioca starch (TS) blend (CMC/TS) incorporated with TiO2 nanoparticles and Dendrobium orchid flower (DOF) extract. The result showed that the DOF extract contained peonidin-3,5-O-diglucoside and exhibited distinguishable color changes in different pH buffers. Likewise, the CMC/TS+TiO2+DOF film’s color changed corresponding to the extract. The X-ray diffraction analysis revealed the expansion of the film’s amorphous region, due to the intermolecular interactions. Analyzing scanning electron microscope images showed the effects of TiO2 and DOF extract on the surface morphology of films. The incorporation of TiO2 and DOF extract into the film formulation improved various film properties, such as redness, opacity, tensile strength, and water solubility. For the sensitivity testing, the color of the CMC/TS+TiO2+DOF film responded to ammonia vapor more than acetic acid vapor, suitable for monitoring seafood spoilage behavior. In addition, the application of film for monitoring the freshness of fish fillets was conducted. The CMC/TS+TiO2+DOF film color changed from purple to bluish-purple corresponding to the spoilage of samples. Indicating its potential as an indicator for monitoring fish fillets' freshness.