Investigation of sodium binding through implementation and application of single- and double-quantum filtered 23Na NMR spectroscopy

Sodium;Sodium-23 Nuclear Magnetic Resonance (23Na NMR);Sodium mobility;Sodium binding;Viscosity;Emulsions

Defnet, Emily ; Schmidt ; Shelly J.

关键词: Sodium;    Sodium-23 Nuclear Magnetic Resonance (23Na NMR);    Sodium mobility;    Sodium binding;    Viscosity;    Emulsions;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/88112/DEFNET-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Reduction of sodium in foods is a top priority in today’s food industry. However, sodium removal, due to its vital importance as a tastant, as well as its contribution to many other food properties, is no simple task. A method that would measure sodium ion mobility and correlate to saltiness perception would be of great value. 23Na NMR spectroscopy is such a method, since it offers a unique means for non-invasively measuring both sodium content and mobility using recently developed single-quantum (SQ) and double-quantum filtered (DQF) NMR experiments. In food products, sodium ions exist in two environments – free (unassociated) and bound (associated). Free sodium ions are mobile in the aqueous phase, whereas bound sodium ions are associated with negatively charged functional groups in the system, such as amine and carboxyl groups associated with protein and carbohydrate macromolecules. The SQ NMR experiment provides information regarding the total sodium ion population in the system, while the DQF experiment specifically focuses on the population of bound sodium ions. Recently, the concentration of free sodium ions, measured using the 23Na NMR SQ-DQF methods, was shown to strongly correlate to saltiness perception in cheeses. Therefore, it is important to investigate sodium ion binding, using a relative ratio of bound to total sodium, in specific food systems, and how that binding changes as a function of sodium ion addition and removal from the matrix. However, the SQ and DQF 23Na NMR methods have never before been established here at the University of Illinois at Urbana-Champaign. Thus, the first objective of this study was to implement the 23Na NMR methods using a 1% (w/w) iota-carrageenan system and verify the method with previously published literature data. The second objective was to apply the 23Na NMR SQ and DQF methods to both reduced-fat (30%) and low-fat (20%) model emulsion systems, meant to model a ranch salad dressing, containing water, oil, soy lecithin, xanthan gum, and NaCl, where added sodium concentrations ranged from 0 to 350mg per 30g serving. Two fat levels were studied since differences in fat content have been shown to have varying effects on saltiness perception. The SQ and DQF 23Na NMR methods were effectively implemented and verified using an iota-carrageenan system. In addition, the relative quantification of bound to total sodium was determined for the model emulsions, and correlations were investigated between sodium mobility (T1 and T2), sodium binding (ADQ/ASQ), viscosity, and pH. It was found that the ratio of bound to total sodium (ADQ/ASQ) remained constant for the reduced-fat formulations, but decreased for the low-fat formulations, indicating the potential of more free sodium in the low-fat versions. It was also found that the reduced-fat formulations had a higher viscosity than the low-fat emulsions, which could contribute to the need for more added sodium in the higher fat formulations. With a greater understanding of the effect of sodium binding on saltiness perception in specific food systems, those systems can be more efficiently engineered to maximize saltiness perception, while containing the least amount of sodium possible.