Gold nanoparticle based smart packaging for differentiating fresh and frozen fish

Abstract

Fresh and refrigerated fish are highly preferred form of fish as it preserves natural culinary properties. Marketing frozen thawed fish as fresh fish is a common ill practice followed in many countries. At present, there is no mechanism to detect this fraud practice by the consumers. Hence, the present work was undertaken to develop a smart packaging device using gold nanoparticles to distinguish packed fresh fish from frozen variety. Gold nanoparticles prepared under isothermal conditions using trisodium citrate were compared with chitosan of four different degree of deacetylation. The developed AuNPs were characterised for UV-visible spectra, FTIR spectra and visible colour changes. The time taken to reduce gold atom to gold nanoparticles varied with the type of reducing agent. The visible colour of the AuNPs prepared using different reducing agents was ruby red colour and the maximum absorbance was between 517 to 528 nm. AuNPs were exposed to frozen storage condition and evaluated for its characteristics. UV-visible spectrum for AuNPs prepared using TSC and lower concentration of chitosan showed a distinctly different broader spectrum with reduced peak intensity. Peak shifting towards right was also observed. This could be due to the aggregation of AuNPs in frozen condition. The ruby red colour of the AuNPs changed to slightly greyish upon exposure to frozen condition for TSC and lower concentration of chitosan indicating its application as smart packaging to distinguish packed fresh and frozen fish.