Development of a cellulose-based freshness sensor I - Filter paper and dye concentration effective for the color expression of pH-Sensitive Dye -

Abstract

This study was conducted to determine a filter paper suitable for a carrier of pH-sensitive dyes and the concentration of pH-sensitive dye for developing a cellulose-based sensor that can provide food freshness to consumers. The pH-sensitive dye, an indicator that provide information about food freshness, was prepared with methyl red and bromothymol blue at a ratio of 3:2, and was diluted to 21, 25, 30, 50% in ethanol and adjusted to pH 10. The physical properties of various filter papers were measured, and then the filter papers were immersed in the indicator for 12 hours and dried. Finally the a value of filter paper dyed with the indicator was measured to identify clear color change according to pH. The result of analyzing the correlation between the main properties of filter paper and a value showed that the pore size of filter paper was the most important factor that affected the color expression. Moreover, the smaller the pore size of filter paper could acquire lower a value. As the concentration of the pH-sensitive dye increased, the a value decreased but the correlation between a value and the pore size of filter paper decreased. Therefore, it is important to select the filter paper with relatively small pore size and a final pH-sensitive dye concentration of 25% or less in order to show a low a value so that a clear color change of freshness sensor can be observed. ? 2020 Korean Technical Assoc. of the Pulp and Paper Industry. All rights reserved.