Taste perception of monosodium glutamate (MSG) in foods in young and elderly subjects

The purpose of this study was to determine the concentrations at which young and elderly subjects were able to detect and recognize monosodium glutamate (MSG) and MSG with 0.5 mM inosine-5'-monophosphate (IMP) in various food media including meats, vegetables, and soups. The most preferred concentration levels of MSG and MSG (with IMP) in the foods were also determined. Detection thresholds for MSG (with IMP) in foods were elevated in elderly subjects compared with young subjects. The detection thresholds for elderly subjects for MSG with IMP in foods were an average of 2.8 times higher than the same detection thresholds for young subjects. The variability among subjects in the ability to detect MSG (with or without IMP) in every food was far greater than the variability found previously in water solutions, especially for young subjects. Adding 0.5 mM IMP to the MSG did not significantly affect detection thresholds in foods. However, preference scores of both young and elderly subjects were significantly higher for the MSG with IMP condition than the MSG alone condition for some foods. Optimally preferred concentration levels of MSG in foods tended to be lower than the level at which MSG is detected or recognized in the food but above the detection threshold for MSG in water. The mechanism by which MSG can be preferred at a subthreshold concentration in foods is not fully understood. One possibility is that MSG synthesizes with food chemicals and forms a new taste quality.