RESUMO
Milk and milk products are an essential part of global nutrition and the world-wide food industry. Studies of milk components using scattering techniques are well documented in the literature. However, those studies focused on the q scattering wavevector region 10 - 3 < q < 2 Å - 1 . This manuscript presents scattering results in the region 3 × 10 - 5 < q < 2 × 10 - 2 Å - 1 , a region that allows the simultaneous study of fat globules and proteins found in commercial food-grade milk. The small and ultra-small angle neutron scattering (SANS and USANS) measurements show that a model based on the Schulz distribution function using uniform spheres was a reasonable choice to successfully fit the scattering features below q = 0.007 Å - 1 . Contrast measurements using D2O on whole milk were carried out to distinguish fat from protein signals. Casein micelles were found to have mean diameters of 96 ± 10 nm with 33% polydispersity. The average scattering length density of the micelles varied from -0.04 × 10-6 Å -2 in homogenized, pasteurized commercial milk to 2.8 ×10-6 Å -2 with 50% dilution by D2O, with a match point of 43 ± 3%, as seen in previous studies. It was found that the average diameter of fat globules in homogenized whole milk was 0.47 ± 0.04 µm with a polydispersity of 45 ± 5%, and a volume fraction of 0.034 ± 0.002 when the scattering length density is fixed at 0.20 × 10-6 Å -2. These USANS measurements provide an important foundation as similar techniques are employed to study cheese varieties and cheese formation.
