Kyle Okada and Youngsoo Lee

Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign

Foods with a lipid/protein-based matrix, such as processed cheeses and meats, are of great interest in sodium reduction research. This interest is due to their prevalence in the diet, their relative contribution to dietary sodium, and the role of sodium in food texture and stability.  The objective of this study was to determine how formulation and processing parameters affect sodium ion mobility in a model lipoproteic gel.
Heat-set model lipoproteic dairy gels were prepared with varying levels of protein (whey protein isolate, 8 and 11 % w/w), lipid (anhydrous milk fat, 0, 11, and 22 % w/w), and NaCl (1.5 and 3.5 % w/w), homogenized under different levels of high pressure homogenization (14 and 55 MPa). 23Na NMR spectroscopy was used to characterize sodium ion mobility in terms of relaxation times (T1 and T2) and creation time (τopt), which have been correlated to saltiness perception in food systems previously. Single- and double-quantum filtered experiments were conducted to characterize the mobility of total sodium ions and sodium ions in a restricted mobility state (‘bound’ sodium), respectively. The relative amount of ‘bound’ sodium was determined by comparing the single- and double-quantum filtered signals. t-tests and ANOVA were used to analyze the effects of formulation (protein, lipid, NaCl concentrations) and processing (pressure) parameters.
The mobility of total sodium ion was decreased (lower T1 and T2) in gels with higher protein or fat content, while changing homogenization pressure did not have an effect. The gels with increased protein, fat, or homogenization pressure had a more ordered structure surrounding ‘bound’ sodium (indicated by a smaller τopt) and more relative ‘bound’ sodium. Increasing NaCl concentration in the range of 1.5 to 3.5 % (w/w) resulted in a significant increase in τopt.
This study highlighted how the mobility of sodium ions is affected by formulation and processing parameters. Sodium reduction requires a deeper understanding of the relationship between sodium ion availability, food microstructure, and desired sensory properties. The data obtained in this study provides information on factors affecting sodium mobility and availability, which can be applied towards sodium reduction in lipid/protein-based foods.