Water mobility in cheese by means of Nuclear Magnetic Resonance relaxometry

Abstract

1 H NMR relaxometry studies have been performed for different kinds of cheese in order to enquire into mechanisms of water mobility in the cheese structures. The exploited frequency range, from 4 kHz to 40 MHz, allowed probing water dynamics on a broad range of time scales. Two fractions of water of much different dynamical properties, referred to as confined-water and free-water, have been revealed. It has been demonstrated that dynamics of water molecules confined in the macromolecular matrix is about four orders of magnitude slower compared to bulk water, while the second fraction exhibits dynamics by slower only by one order of magnitude. It has turned out that the differences in the water behaviour and, hence, macroscopic properties of cheese are related to differences in the relative populations of these fractions and the portion of water molecules bound to proteins, while the time scale of water dynamics is similar for all cases. • NMR relaxometry allows to probe water dynamics in food products. • Cheese includes “confined-water” and “free-water” fractions. • Dynamics of confined water is by four orders of magnitude slower than in bulk water. • Dynamics of water in different kinds of cheese is similar. • Properties of cheese dependent on the population of the water pools.