Effect of Paper Matrix on the Properties of the Ammonia Gas Indicator Label

Indicator labels for detecting ammonia gas are useful for monitoring the freshness of foods such as meat, shrimp and fish because of its simple detection methods. In this research, paper labels made using black glutinous rice extract are used as ammonia gas indicator. The indicator labels were tested by exposing them to ammonia gas obtained from an ammonia solution with a concentration of 0.005%, 0.025%, 0.05%, 0.1%, and 0.5%. The color of the label was scanned using the color scanner equipment and its image was analysed using ImageJ to obtain the RGB component values. The UV-vis spectra of the extract solution at pH 2 and 5 show the absorbance peak at 531 nm wavelength, then shifted to 499 nm for pH 7, 8, and 13. The color of these labels is determined by the pH value of the matrix paper. Once exposed with ammonia gas, the color of the label from Whatman paper changes from red to purplish brown and then to yellow. While the label using HVS paper changed from greyish brown to dark brown. Based on the RGB analysis, the red color component indicates better sensitivity to ammonia gas than the green and blue components. Storage conditions of the labels at low temperatures and in dark show better color stability. These results indicate that the labels of the black glutinous rice extract on Whatman paper matrix can be used as a good indicator of ammonia gas and has the potential to be applied in the monitoring of freshness of meat.