Using 1H and 23Na NMR relaxometry as a novel tool to monitor the moisture and salt distribution in commercial low-moisture part skim mozzarella

Abstract

Zonal variations in 1H or 23Na content in commercial low-moisture part-skim mozzarella with a uniform salt distribution, obtained by dry-salting, or with a salt gradient, obtained by dry-salting and brining, were profiled using a combined 1H and 23Na NMR relaxometry procedure. 1D concentration–distance profiles were constructed in all cheeses from the surface to the core. Rapid, non-invasive, (∼21 min) distinction between dry-salted and brined cheese was enabled. Uptake of salt in cheese brined for 0–24 h was determined, and the derived effective diffusion coefficient of 23Na (3.23 × 10−10 m2 s−1) compared favourably with values reported for other semi-hard cheeses during brining; the 23Na concentration–distance profiles of brined cheese stored for 2–44 d at 4 °C corresponded to an effective diffusion coefficient of about 5.21 × 10−10 m2 s−1. Small variations in moisture content in the cheese could not be distinguished from the random fluctuations in 1H signal intensity.