Temporal Sodium Release Related to Gel Microstructural Properties—Implications for Sodium Reduction

Abstract

The microstructure of food can be engineered to enhance sodium release during mastication, which may be used as a strategy to reduce sodium content in foods. This study aimed to relate sodium release to microstructural properties of solid lipoproteic colloid (SLC) foods. The SLC gels with 1.5% (w/w) NaCl were prepared by homogenization of whey protein isolate and anhydrous milk fat, followed by heat-induced gelation. The gels varied in protein content (8% or 16%), fat content (0%, 11%, 22%, or 33%), and homogenization pressures (14 or 55 MPa). The maximum rate of sodium release during the initial gel compression increased with increasing gel porosity and pore size. This was due to more releasable serum in the gels with larger pore volume and larger pores. The maximum concentration of sodium at the end of sodium release increased with reduced size of the fat particles in the gels. The smaller fat particles were dispersed more uniformly and interrupted the protein network more, and facilitated the gel breakdown. The above findings suggested that, during the breakdown of the SLC gels, the major mechanisms of sodium release are via serum release followed by sodium diffusion, which are governed by the gel porosity and the particle size of fat, respectively. This study demonstrated the dependence of temporal sodium release properties on the microstructural properties of an SLC food system. The findings from this study could lay the foundation for further investigation of the dependence of saltiness perception on SLC microstructure, which can provide insight for sodium reduction in SLC products.

Structural characterization of solid lipoproteic colloid gels by ultra-small-angle X-ray scattering and the relation with sodium release

“…This tendency is because the fat droplets are structural defects, and defects increase the stress concentration of the gel matrix (Sala, van Vliet, Cohen Stuart, Aken, & van de Velde, 2009;van Vliet, Luyten, & Walstra, 1993). This property has been further demonstrated by reductions in the gel fracture strain, stress or energy and by increases in sodium release with higher fat contents or lower emulsion droplet particle sizes in lipoproteic gels (de Loubens et al, 2011;Kuo & Lee, 2014b;Panouille, Saint-Eve, de Loubens, Deleris, & Souchon, 2011;Phan et al, 2008). Our previous study on model solid lipoproteic colloid (SLC) gels revealed that a higher homogenization pressure led to a lower hydrodynamic radius of the emulsion droplets (r h,e ), which implied an SLC gel network with more randomly dispersed structural defects.…”

“…In a model polysaccharide/protein gel, the serum release was found to be higher in a bi-continuous microstructure than in a protein-continuous one (Stieger, 2011). Lastly, the fragmentation degree of lipoproteic foods is greater with higher fat content (de Loubens,et 4 al., 2011), lower protein content (Panouille, et al, 2011), or smaller particle size of the emulsion droplets (Kuo and Lee, 2014b).…”

“…The increased sodium release in lipoproteic foods associated with smaller emulsion droplets was ascribed to the higher surface area after the food breakdown (Kuo & Lee, 2014b). When emulsion gels undergo deformation, the initiation of fracture more likely starts at the interface between fat and protein than between protein and protein.…”

“…More structural defects thus led to easier fracture and higher surface area of the fractured debris. However, the increase in sodium release with reduced r h,e was not universally significant (Kuo & Lee, 2014b). Because the r h,e was obtained from dynamic light scattering (DLS) of the emulsions prior to the heat-induced gelation, we hypothesized that the particle size of the actual fat globules within the lipoproteic gel correlates better than the emulsion r h,e to the fragmentation degree and thus the release of sodium.…”

Controlling sodium release using maltodextrin and octenyl‐succinic‐anhydride‐modified starch with two types of spray‐dryer nozzles

“…Extracted parameters from the curves can be used to quantify the sodium release (Kuo & Lee, ). In this study, four parameters were chosen to represent the sodium release profile (Christina & Lee, ): the maximum of sodium release rate ( R max ), the snapshots of sodium concentration at 20 s ( C 50 ), 50 s, and 50 s ( C 150 ).…”