Effects of formulation and processing parameters on sodium availability in a model lipoproteic emulsion gel

Sodium reduction in processed foods is a high priority in the food industry due to the health implications of excessive dietary sodium consumption. Foods with a lipid/protein-based (lipoproteic) emulsion structure (such as processed cheeses and meats) are of particular interest because of their contribution to dietary sodium and the role of sodium in desired sensory and textural properties. When reducing sodium content in these food systems, it is crucial to understand the physicochemical and matrix properties contributing to sodium availability and saltiness perception. The overall objective of this study was to characterize chemical and rheological influences on sodium availability in a model lipoproteic emulsion gel. There were three specific aims to accomplish the overall objective. The first aim was to characterize the effects of formulation and processing parameters on sodium ion molecular mobility and binding in the model gel system. The second aim was to characterize how altering formulation and processing parameters affected rheological and structural properties. The third aim was to correlate the measured mobility and rheological properties with sensory perceived saltiness and texture attributes. To accomplish these objectives, model lipoproteic gels formulated with varying protein, fat, and NaCl content and processed with varying homogenization pressure were prepared. Sodium ion molecular activity was characterized with 23Na nuclear magnetic resonance (NMR) spectroscopy. Single quantum (SQ) experiments were used to characterize the mobility of overall sodium in the system, while double quantum filtered (DQF) experiments were used to characterize sodium in a restricted mobility ('bound') state and quantify relative 'bound' sodium. Formulation and processing parameters were found to influence gel structure and sodium matrix-interactions. Increasing protein or fat content reduced sodium mobility, and increasing protein or fat content or homogenization pressure increased the amount of relative 'bound' sodium. Rheological and structural properties were characterized with small deformation oscillatory rheometry and creep compliance/recovery rheometry. Gel mechanical behavior was successfully modeled with a four-component Burgers model, and it was found that increasing protein, fat, or salt content or homogenization pressure resulted in a stronger and more solid protein network structure. The results from the 23Na NMR and rheometry experiments were correlated with sensory taste and texture properties obtained by quantitative descriptive analysis (QDA). Salty taste and syneresis texture correlated positively with sodium mobility and elastic compliance, and correlated negatively with dry matter content, relative 'bound' sodium, and gel firmness. This study found that formulation and homogenization pressure significantly influence sodium behavior and rheology in lipoproteic emulsion gels, which may have significant implications for saltiness perception and sodium reduction. The results suggest that saltiness perception can be influenced by altering sodium availability via modulation of molecular interactions, texture, and sodium release. Future research could explore increasing saltiness perception by introducing species that compete with sodium for binding sites to increase sodium availability