A colorimetric label for detecting acetic acid vapor using Ipomoea pes-caprae flower extract as a functional dye

Colorimetric labels used to detect acetic acid vapor are becoming very popular as they are useful for directly monitoring the freshness of dairy products. In this paper, an investigation of a colorimetric label made of tracing paper dyed with Ipomoea pes-caprae flower extract to detect acetic acid vapor was reported. For extraction of Ipomoea pes-caprae flowers have been used maceration method. The absorbance spectrum as a function of the pH of the extract solution has been measured with UV-Vis spectrophotometer equipment. These labels were tested for detecting of acetic acid vapor produced by the solutions of various concentrations for 12 hours. The labels were then scanned with a flatbed scanner, and then its image has been analysed using ImageJ software to obtain its RGB color component. The label was originally green and after detecting acetic acid vapor the color changed to pink. The greater concentration of acetic acid solution provides a change from the color of the labels more quickly. The red components of the RGB show the highest sensitivity to acetic acid vapor. Results of the stability against the temperature and humidity of the label color test indicate that the color is more stable when stored at 10 °C and 55% relative humidity. Based on these results, this colorimetric paper label can be used as a monitoring label for freshness of dairy products.