Dynamic water profile in various types of cheese analyzed by means of nuclear magnetic resonance relaxometry

The aim of the study was to enquire to which extend ¹H spin-lattice nuclear magnetic resonance (NMR) relaxometry data collected over a broad range of resonance frequencies (from 10 kHz to 10 MHz) have the potential to be used for assessing quality and authenticity of different categories of cheese. The following cheeses were selected mozzarella, processed cheese, pizza cheese, pizza cheese with modified fat phase), low-fat cheese, and long ripened cheese. The cheeses from 3 different production plants and various cheese production batches were used in the study. The samples from each group were subjected to instrumental composition analysis (FoodScan analyzer type 78810, FOSS, Hillerod, Denmark), water activity assessment (Aqualab 4TEV analyzer, type S40001855) and nuclear magnetic resonance relaxation dispersion study (SMARtracer FFC relaxometer, Stelar S.r.l, Italy). The state and dynamics of water present in products as free and bound water largely determines the properties of food products, including cheeses. Nuclear magnetic resonance relaxometry studies of cheese enable to reveal relaxation features characteristic of specific categories of cheese. Consequently, the studies can be treated as a step toward exploiting NMR relaxometry for accessing quality and authenticity of cheese. It was shown that at low resonance frequencies, the lower the moisture, the larger the relaxation rate. The durability and quality of cheeses depend on the presence and condition of water, so it is necessary to find a relationship between the presence, condition and mobility of water in cheeses, to increase and improve the quality and extend the shelf life.