A Meta-Analysis on The Effect of pH on Curcumin Natural Dye Halochromic

Abstract

It is recorded in much previous research that curcumin has been used to monitor the changes in pH in some products. However, a quantitative study in analyzing and combining results from various research, especially on the effect of pH in halochromic curcumin natural dye against the color characteristics, has not been studied yet. A preliminary study was done to know the trend of halochromic natural dye in Scopus. As the result, carotenoids and curcumin were the top two trending topics from 2017 to 2021 as proven by 18,704 and 16,279 journals respectively talking about these natural dyes. Meta-analysis in this research was carried out by searching “curcumin”, “pH indicator”, and “freshness monitoring” as keywords in the database from 2012 to 2022 with google scholar, crossref, and science direct. The data obtained were from 18 journals with 29 studies and 211 sample data. Firstly, the data was examined throughout its collinearity to ensure each variable was independent thus the model will result in highly reliable statistical inferences. Then, the data were further analyzed using parameters, such as the L* value, a* value, b* value, total color difference, chroma, and hue by applying a linear mixed model. The visual color of halochromic curcumin natural dye turns from bright yellow to dark red color as pH increases. The results of the analysis model with pH between 1 to 14 had a highly significant impact with P≤0.001 in the decreasing of L* value, b* value, total color differences, hue, and chroma. On the contrary, pH brought a significant impact on the increasing of a* value with P≤0.001. The addition of the matrix to curcumin natural dye affects the intensity of color changes. The results of the independent t-test statistical analysis showed a significant effect (P≤0.05) with a visible reduction of the L* value, b* value, total color difference, and chroma, while the a* value and hue had no significant (P>0.05) effect with respectively an invisible increasing and decreasing.