Use of color sensor device with resazurin test for rapid screening of raw milk with low microbiological quality

Abstract

The microbiological quality of raw milk is important for the dairy industry because it can directly affect the quality and shelf life of dairy products. To evaluate the microbiological quality of raw milk, the resazurin test, a rapid dye reduction assay, was commonly used. However, resazurin test results are usually read by the eye, which can cause errors in judging the milk quality. In this study, a color sensor device based on the RGB system for measuring the color resulting from the resazurin test was developed. The device was embedded with VEML6040, an RGB-based color sensor, and operated using an Arduino microcontroller. The results showed that there is a reverse correlation between the percentages of the blue color and the number of microorganisms, both with the resazurin test performed in test tubes and in reduced-scale microtubes. A linear regression line with an R² of approximately 0.85 was obtained from the plot between the percentages of blue values from the microtube resazurin test and the corresponding numbers of microorganisms. This suggests that using the blue values to classify milk according to its microbiological quality is possible. With the present dataset, the blue value of 25% could be used as a cut-off value to separate raw milk with microbial loads of 7 log cfu/ml or higher from milk with lower microbial loads.