Chitosan-capped gold nanoparticles for indicating temperature abuse in frozen stored products

The present study aimed to optimize the conditions for the synthesis of gold nanoparticles (AuNP) using chitosan and to assess its effectiveness as temperature threshold indication for frozen storage conditions. Chitosan concentration of 0.25% and temperature of 90 degrees C for 15min was optimum for synthesizing AuNP. The maximum absorbance (lambda (max)) was observed at 530 and 540nm for 0.125% and 0.25% chitosan, respectively, indicating shifting of peak toward longer wavelengths (red shift) with increasing chitosan concentration indicating larger AuNPs. A prominent absorption peak at 1367cm(-1) by Fourier transform-infrared (FTIR) spectrum corresponding to C-C stretching of the glucosamine group of chitosan indicates the chitosan capping on the AuNP. Higher peak intensity and a peak shift toward shorter wavelength were observed for AuNPs exposed to frozen temperature abused conditions. Distinctly clear visible color variation from cherry red to gray indicates its application as temperature abuse indicator in frozen products. Sensors: Chitosan capped gold nanoparticles indicate storage temperature historyThermal history indicators (THI) attached on packages can tell us the storage temperature history of food and pharmaceutical products, which influences their quality and safety a lot. Metal nanoparticles are widely considered as THI. Mohan from ICAR-Central Institute of Fisheries Technology, India and coworkers reported a temperature abuse indictor based on chitosan capped gold nanoparticles. Chitosan was used as a reducing and stabilizing agent in the synthesis of gold nanoparticles. The final size of Au nanoparticles was determined by the used concentration of chitosan. The chitosan capped gold nanoparticles were capable of altering color and color intensity when exposed to temperature fluctuations. This can be attributed to the aggregation of the gold nanoparticles, alteration in shape and size at frozen temperature abused conditions.