Quantifying anisotropy in mozzarella cheese using spatially resolved shortwave NIR spectroscopy

The anisotropic structure of Mozzarella cheese governs its texture and functionality in applications such as pizza. The pasta-filata process that forms a fibrous protein network creates anisotropy in Mozzarella. Variations in cooker-stretcher parameters, including temperature, rotor speed, and additives, affect the anisotropy and consequently the functional properties of Mozzarella. The traditional mechanical testing methods, although informative in assessing texture, do not describe the relation between macroscopic properties and molecular-level structural arrangements. This study presents a novel approach utilizing spatially resolved shortwave near-infrared spectroscopy (SW-NIRS, 761-1081 nm) to characterize and quantify anisotropy in Mozzarella cheese. Nineteen designed Mozzarella samples were analyzed using two experimental setups. The first was a two-axis orthogonal measurement, where spectra were collected by measuring along two orthogonal sample axes corresponding to protein fibers aligned parallel and perpendicular to the light path. The second was a spinning setup, in which samples were placed on a rotating disc, and spectra were continuously collected over four complete 360° rotations within 40 s. Spectral data were acquired over five different distances from the illumination. Spectral variation, scattering, and absorbance were quantified using multiplicative scatter correction parameters and regression analysis, demonstrating a high correlation between anisotropy and optical measurements (r² = 0.81). Spatially resolved SW-NIRS thus provides a rapid, non-destructive tool for evaluating the structure-function relationship in Mozzarella cheese, with potential applicability to other food systems exhibiting significant anisotropic structures.