Technical note: Characterizing individual milk fat globules with holographic video microscopy

Schematic representation of holographic video microscopy. The sample scatters light from a collimated laser beam. Both the scattered and unscattered laser light are collected by an oil-immersion objective lens and relayed to a video camera, which records their interference as a hologram. A typical example of one fat droplet's hologram is shown to the right, together with a fit to equations . N.A. = numerical aperture.

Histograms of (a) fat droplet radii and (b) refractive indexes obtained from single-droplet characterization measurements.

Scatter plot of refractive index and globule radius a for commercial milk samples. Each data point represents results for a single fat droplet. Error bars are computed from the normalized covariance matrix of the fitting parameters. Histograms at the top and side show the number-weighted distribution of values of the radius and refractive index, respectively.

Refractive index versus droplet radius, a, for dispersed Type B immersion oil in water, both with (squares) and without (circles) surfactant.