A new design of colorimetric films using bacterial cellulose nanocrystals derived from nata de coco for sensing volatile organic compounds.

In this work, bacterial cellulose (BC) derived from Nata de Coco is a polysaccharide material, and it is further processed into bacterial cellulose nanocrystal (BCNC) via acid hydrolysis. Then BCNC is doped with transition metals to enhance its amine/hydrogen sulfide response. Therefore, the aim of this study is to investigate the use of transition metals as indicators to detect amine and hydrogen sulfide gas for efficiently monitoring food spoilage. BCNCs were treated with various concentrations of silver nitrate (AgNO3) and copper sulfate pentahydrate (CuSO4·5H2O). Then the dropwise addition of ascorbic acid was applied to reduce Ag+ and Cu2+ to Ag0 (silver nanoparticle) and Cu0 (copper nanoparticle), which refer to red brown and red wine colors, respectively. The results indicated that BCNC/Ag nanoparticles were spherical, while BCNC/Cu nanoparticles exhibited a rod-like structure. XRD results also presented the incorporation of Ag and Cu nanoparticles, as confirmed by both crystallography structures. Furthermore, UV-Vis spectra showed the adsorption bands at 422-430 nm and 626-629 nm, belonging to Ag and Cu nanoparticles. After H2S and ammonia gas exposure, BH/Ag and BH/Cu films turned black from brown and red. In conclusion, transition metal-doped BCNCs exhibit potential for innovative food spoilage gas sensors.

Fabrication of a colorimetric film based on bacterial cellulose/metal coordination framework composite for monitoring food spoilage gas.

A newly designed colorimetric sensing film has been developed to determine the spoilage gas from food deterioration. The fabrication of sensing film used for food labels based on bacterial cellulose and carboxymethyl cellulose composite film (BC/CMC) incorporated with Bis(imidazolium) tetrachlorocuprate, HIm2CuCl4 was focused. The BC/CMC composite films were prepared by vacuum filtration and then dipped into the (5-20 % w/w) HIm2CuCl4 solution. Subsequently, they were dried at 60 °C to obtain the BC/CMC-Cu film. For monitoring fish freshness, the TVB-N level was considered an indicator of determining fish spoilage. In addition, the color change was evaluated and expressed as Lab color values and total color difference (TCD). According to the sensing response, the TCD values of the sensing films had continuously changed, corresponding to the ammonia gas, which is one of the TVB-N gases. Based on the variations in Lab color values exposed to ammonia gas at room temperature, the film color shifted from the initial lime green color to the final blue color due to the substitution of metal-ligand bonding. Finally, this colorimetric sensing film can be employed as a potential food freshness indicator in intelligent packaging.