Detection of Water and Glucose Adulteration in Cow Milk by Innovative Speckle Pattern Imaging

Milk adulteration is a frequently reported type of food fraud and poses significant social and economic challenges worldwide. One of the most common types of milk adulteration involves dilution with water or water-glucose solutions. In this article, we demonstrate an optical, contactless method to discriminate different types of commercial milk (whole, partially skimmed, and skimmed) and identify its adulteration with water and 12.5% water-glucose solution that was selected since it exhibits a refractive index (RI) comparable to that of whole milk. For this reason, the latter kind of milk adulteration could remain unnoticed when performing quality test based on RI measurements. Our proposed optical configuration employs a complementary metal-oxide–semiconductor (CMOS) digital camera to acquire speckle pattern (SP) images generated by shining the beam of a red semiconductor laser onto milk samples placed in a plastic cuvette. The collected data are then analyzed to extract informative parameters, such as the average intensity and the speckle grain size. The results show that our system can distinguish between different types of milk and detect diluted samples with both water and glucose, offering a reliable approach to address milk adulteration and ensure the integrity of dairy products on the market.