Structure and composition of flavoured model cheeses impact on sodium and aroma release

Health authorities have called for a reduction of salt quantity in various foodstuffs. Cheese is one of the most targeted products because of its high sodium content. In order to understand how to reduce salt in cheeses without modifying salty perception, the interactions between cheese structure and in-mouth sodium release have to be studied. In this way, model cheeses have been selected due to their great variability of formulation. The current study was conducted to determine how the release of sodium ions and aroma compounds could be modified by structure and composition of model cheeses (lipid/protein ratio, sodium content...). The experimental approaches were performed by in vitro and in vivo investigations. Sodium mobility in model cheeses was analysed by 23Na Nuclear Magnetic Resonance (NMR) spectroscopy. Diffusion and partition coefficients of sodium ions between cheese and water were obtained from in vitro measurements. Microstructural properties of model cheeses were analysed with Confocal Laser Scanning (CLS) microscopy and textural properties were characterized by rheological measurements. Then, aroma release was investigated by Atmospheric Pressure Chemical Ionization Mass Spectrometry (APCI-MS) during cheese consumption. Significant differences between model cheeses were found concerning sodium and aroma release. 23Na NMR spectroscopy turned out to be an accurate method to quantify the total amount of sodium. Moreover this spectroscopy gave information on Na+ ions distribution, mobility and environment. Indeed, the presence of a fraction of 'bound' sodium ions was evidenced in all the cheeses. The hard model cheese with low lipid/protein ratio showed a higher fraction of 'bound' Na+ and a more specifically ordered environment around the ions. These aspects could be linked to lower diffusion and partition coefficients found in the hard model cheese, highlighting a lower sodium release. . In addition, aroma release was studied by APCI-MS. The in vivo experiments showed that aroma compounds were more released from the hard flavoured model cheese (low fat content) than the soft one. The results were relevant either with in vitro conditions or with in vivo consumption of model cheeses. In view of these results, it is obvious that composition, structure and micro-organisation mostly determine sodium and aroma release in model cheeses.