Identification and Authentication of Milk Using Digital Colormetry of Indicator Test Systems, Smartphone, and Chemometric Analysis

A simple and an available method is proposed for the identification and authentication of milk using a test device, a smartphone, and chemometric analysis. For the identification by the region of origin and the species of milk (cow, goat, sheep, etc.) and authentication (authenticity, falsification of milk), acid-base indicator papers and test papers are used to determine the total hardness and total alkalinity of water and chloride and sulfate ions. Two indicator systems are proposed. In the first test system, 16 indicator zones are used, of which 12 zones are acid-base indicators with a color change in the pH range of 3–9, and 4 are indicator zones, the color change of which depends on the concentration of calcium ions and chloride, sulfate, carbonate, and hydrocarbonate ions. The second test system uses fluorescent indicators, as well as the intrinsic fluorescence of milk on cellulose paper and a thin silica layer. In this case, the indicator zones of the matrix are irradiated with monochromatic ultraviolet light (365 nm) after applying milk samples to them. A device and a method for measuring the colorimetric characteristics of test systems using a smartphone are proposed. The data array (the sum of the RGB channel values) is processed using the XLSTAT software. The use of chemometric analysis made it possible to establish the authenticity of milk, identify it by the region of origin, and reveal facts of milk falsification by dilution with water, the use of vegetable fats, and emulsification with surfactants. The manufacturers of pasteurized milk were identified and a possibility of determining its fat content by the data array of RGB colorimetric parameters is proved