Abstract:
A colored pH sensor for fresh fish packaging has been newly developed to evaluate the fresh fish spoilage during transport and storage. The processing of pH-sensitive film used for fish packaging based on the layer of organomodified clay nanocomposites laminated with the layer of indicator dye was focused. The nonoclay composites were prepared via melt compounding through a twin screw extruder by using Surlyn® as a reactive compatibilizer. Subsequently, the pH sensor was fabricated by using a spin-coater and was attached to PP/clay nanocomposites films using a laminating machine (at 160°C). Fish spoilage was assessed for aerobic plate count (APC) and total volatile basic nitrogen (TVB-N). The color changes of the pH sensor were measured and expressed as Hunter values and the total color difference (TCD). The TCD values of bromocresol green (BCG) type indicator also changed continuously with the response of the indicator. The color changes of the pH sensor correlated well with the APC and TVB-N values of fresh fish. According to the changes in Hunter color values of the indicator within the packages of fresh fish at room temperature, the color of the pH sensor turned from an initial yellow to a final green for BCG type. The color changes of the developed pH sensor film properly represented the spoilage of the fresh fish. By laminating pH sensor on nanocomposite film, the layer of nanocomposite can facilitate the gas barrier properties and the leakage of indictor. As the final product, these pH sensors could be employed as an effective, smart packaging technology for evaluating fish freshness.
