A novel refractive index based-fiber optic sensor for milk adulteration detection

Milk adulteration poses a significant risk to public health and consumer trust, compromising its nutritional value. To address this, we've developed an optical fiber-based sensor using a Lossy Mode Resonance (LMR) approach. Antimony Oxide (Sb2O3) serves as the sensing layer, deposited onto the optical fiber's unclad core using Radio Frequency Magnetron sputtering. The sensing layer underwent comprehensive characterization, including X-Ray diffraction (XRD), UV-Vis spectroscopy, Ellipsometer, Atomic Force Microscopy (AFM), EDAX, and Field Emission Scanning Microscopy (FESEM). The sensor was tested for formaldehyde and water adulteration across normal milk type 1, full-fat milk type 2, vendor milk type 3, and, with concentrations ranging from 0 % to 10 %. Observations included resonance wavelength shifts and sensing parameters such as sensor response, sensitivity, and repeatability. For Sb2O3-coated sensor probes, responses to formaldehyde and water adulteration for type 1 milk is 2.05 % and 2.22 %, type 2 milk is 2.17 % and 2.4 %, and type 3 milk is 1.90 % and 1.95 %. Sensitivity for Sb2O3-coated probe to formaldehyde are 2.2 nm/v% (type 1 milk),1.9 nm/v% (type 2 milk) and 1.5 nm/v% (type 3 milk). For water in milk, the sensitivities are 1.7 nm/v%, 1.5 nm/v%, and 1.2 nm/v%. Furthermore, a prototype sensor probe has been developed for continuous milk adulteration monitoring, interfaced with Arduino and Thing Speak.