Monosodium glutamate and saltiness: biomolecular analysis of psychophysical evidence

OTERO-LOSADA, M.

Dijon, France

Congreso; Sixteenth Annual Meeting of the European Chemoreception Research Organisation (ECRO); 2005

European Chemoreception Research Organisation (ECRO)

  MSG-induced enhancement of saltiness was evaluated using conventional psychophysical methodology (converging limits, CL). Stimuli: aqueous solutions of NaCl, NaCl+MSG, NaCl+KCl, NaCl+MSG+KCl, KCl, MSG and KCl+MSG. Concentrations: NaCl 12.5, 25, 50, 100, 200 mM; KCl:NaCl ratio 2:1; MSG 4.32, 10.80, 27.00, 67.50, 168.75 mM (27 mM in mixtures). CL estimations were plotted against concentration and psychophysical slopes (b, Steven's coefficient) calculated. Results were analysed by two-way ANOVA followed by the least significant difference test (LSD).   b values, r2 (regress. coeff.) were: 0.80 ± 0.06, r2=0.98 (NaCl); 0.60 ± 0.01, r2=0.99 (NaCl+MSG); 0.69 ± 0.04, r2=0.99(NaCl+KCl); 0.65 ± 0.04, r2=0.99 (NaCl+MSG+KCl); 0.49 ± 0.05, r2=0.97 (MSG); 0.66 ± 0.02, r2=0.99 (KCl); 0.58 ± 0.04, r2=0.99 (KCl+MSG). Concentration (P<0.0001), panelist (P< 0.0001) and salt (P< 0.001) affected S and salt interacted with concentration (P<0.0001). KCl and (NaCl+MSG+KCl) were different to MSG, NaCl and NaCl+MSG (LSD, P<0.05).   Results showed that b NaCl >bKCl >b MSG. MSG or KCl flattened the response to NaCl and MSG specifically affected NaCl. MSG addition to NaCl+KCl mixtures did not enhance saltiness. b NaCl decrease induced by MSG or KCl resulted from increased saltiness at low NaCl+ levels. Data analysis according to Beidler's equation (tastant-receptor binding model for taste) suggested a likely biophysical interaction with Na+ binding sites in taste cells resulting in increased binding affinity and saltiness enhancement by MSG. This effect was found to be NaCl specific.   At present, main alternatives to reduce Na content are KCl or MSG combinations with NaCl. Nevertheless only MSG appears to avoid significant flavor deterioration, a feature decisive at choice time. The characteristics of the biomolecular events underlying MSG effects linked to Na+ specificity is discussed in relation with flavor preservation in low Na+ foods.   Keywords: MSG, saltiness, mechanism, flavor.