Synthesis and Characterization of Polyaniline Agglomerates and Polyaniline Nanoparticles to Use As Printed Sensors to Detect Spoilage of Catfish During Refrigerated Storage

Abstract

There is growing interest in the development of sensors contained in packaging for seafood that are applicable at the consumer level to monitor freshness in a non-destructive manner. Total volatile basic nitrogen (TVB-N) analysis indicates the freshness of seafood. TVB-N analysis is sensitive to the spoilage compounds comprised of ammonia, trimethylamine, dimethylamine, and biogenic amines commonly found in seafood and whose concentration increases when spoilage microbial growth occurs. However, TVB-N analysis is laborious and is not suitable for use at the consumer level. Polyaniline (PANI) is a polymer that may be used as a sensor for detecting TVB-N in seafood. A deprotonated PANI molecule is an emeraldine base which is blue in color, while a protonated PANI molecule is an emeraldine salt which is green in color. Such changes in the polymer’s physical properties may be exploited for sensing purposes. PANI does not leach, is biocompatible, and environmentally stable. The objective of the study was to synthesize and print PANI nanoparticles sensors for the detection of TVB-N spoilage compounds in catfish stored at 4°C in the refrigerator. In this study, PANI agglomerates and PANI nanoparticles (NPs) were synthesized via the slow-drip and rapid mix methods, respectively. The PANI agglomerates and PANI NPs were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. The PANI NPs were printed onto high-density cardstock paper using a piezoelectric inkjet printer to construct a sensor. The PANI NPs paper sensors were applied to catfish TVB-N volatiles in refrigerated conditions for six days. The CIELAB data of the printed PANI NP sensors in L*, a*, and b* values were recorded and converted to total color difference (∆E*) values. TVB-N titration, pH, and microbial analysis were also conducted on the catfish over the six-day period. The increase in total color difference (∆E*) values obtained from the PANI NPs sensors and the increase in microbial growth in catfish over the six days directly correlated to the increase in the TVB-N produced from catfish in refrigerated conditions. Future research can explore utilization of different substrates for printed PANI sensors applied to seafood.