Ultrasensitive and fast detection of denaturation of milk by Coherent backscattering of light

Abstract

In this work, Coherence backscattering (CBS) of light has been used to detect the onset of denaturation of milk. The CBS cone shape and its enhancement factor are found to be highly sensitive to the physical state of the milk particles. The onset of denaturing of milk not visible to the naked eye, can be easily detected from changes in the CBS cone shape. The onset of denaturation is confirmed by spectral changes in Raman spectra from these milk samples. Further, the possibility to estimate the dilution of milk by water as an adulterant is demonstrated. The method reported has a broad scope in industry for making an inline ultrafast cost effective sensor for milk quality monitoring during production and before consumption.

Quantitative imaging of heterogeneous dynamics in drying and aging paints

“…The many scattering events randomise the transport of the photons, resulting in a diffusion path of the photons through the material 34 . The typical randomisation length is given by the transport mean free path l * , which can be deduced from Mie theory 35 or can be determined experimentally 36 . The diffusion coefficient D 1 of light in a multiple scattering medium is D l = 3 l * c / n , with c = 3 · 10 8 m/s the speed of light in vacuum, n the refractive index of the medium, and l * typically of the order of 10–100 μ m, giving m 2 /s 37 .…”

“…After reflection by a mirror, the beam is expanded to a diameter of ~1 cm by a Galilean beam expander. The beam is then directed downward onto the sample via two mirrors, at a small angle with respect to the detection path to avoid intensity enhancement by coherent backscattering 36 64 . The backscattered light is reflected by a mirror onto a linear polariser perpendicular to the polarisation of the incident laser beam, to filter specular and low-order scattering paths.…”

Laser Speckle Strain Imaging reveals the origin of delayed fracture in a soft solid

“…The samples were cured overnight at 65°C, resulting in highly opaque elastomers that are macroscopically brittle, with fracture toughness K Ic = 0.2 MPa measured by dynamic mechanical analysis (see subsection below) and Young’s modulus E = 1.1 ± 0.1 MPa determined from the initial linear slope of a stress-strain curve (implying a mesh size on the order of [ k B T / E ] 1/3 = nanometers). The photon transport mean free path was measured by coherent backscattering ( 51 ) to be l * = 50 μm (see subsection below). It is important to note that Sylgard 184 contains at least 16 volume % of silica filler, in the form of ~100-nm aggregated silica particles ( 32 ), added by the manufacturer to increase the tear strength.…”

“…The image intensities were azimuthally averaged to obtain the radial intensity decay curve, which was fitted to extract l * as described in the study of Verma et al . ( 51 ).…”

Measuring milk fat content by random laser emission

“…This indicates that visible light can scatter according to the Mie process when it propagates in the bulk of such sample and this could lead to RL emission if a gain medium such as rhodamine is present. Spectroscopic experiments and methods involving light scattering 11 and coherent back scattering 12 were already studied to determine the properties of milk and its denaturation, respectively. The present work proposes a different spectroscopic method where milk protein and fat globules can be detected using RL.…”