Calcium di-glutamate (CDG) could be used make soups with reduced salt levels more palatable, claims new research.
Writing in the journal Food Quality and Preference, the authors said that their results indicated that CDG could partly replace sodium chloride “at constant levels of liking and pleasantness.”
CDG is one of the five glutamate salts internationally accepted as food flavour enhancers.
According to the World Health Organisation (WHO), the current sodium chloride daily intake in western countries ranges between 9 and 12 grams per day (and has been reported to be as high as 16 grams per day in the USA). The current recommendations are to reduce this level to around 5 grams per day.
However a decrease in sodium content is often associated with a decreased consumer acceptance. It is therefore important for industry to compensate for the sensory effects of salt as they reformulate lower sodium products.
The US researchers maintain their findings build on the work of previous studies that have investigated the sensory characteristics of soups containing CDG and other glutamate based compounds.
But the authors, based at the School of Public Health at the University of Washington in Seattle, explained that the earlier research used much more complex soups that contained a range of ingredients.
“The current study used a basic chicken broth and added differing levels of NaCl and CDG, thus our results help to generalize previous findings,” they argue.
Concentrations of sodium
Thirty-four normal weight men and women aged between 20 and 35 years tasted 12 chicken broths containing 4 different concentrations of sodium chloride (.16%, .53%, .85%, and 1.7% w/w) and three concentrations of CDG (0%, .17%, and .33% w/w).
Chicken stock, continued the researchers, was purchased from a single lot at a local supermarket to assure consistency and contained .16% w/w NaCl (150 mg sodium per 240 ml serving). “This base chicken stock allowed for upward adjustment of the total sodium concentration by the addition of CDG and NaCl,” said the authors.
The researchers said the product also met the FDA standards for a ‘reduced sodium’ product (i.e. at least 25 per cent less sodium than the original product) and was close to the standard for the product label ‘low sodium’ (i.e. 140 mg or less sodium per serving).
Participants tasted all the soups twice over 2 days and used computer-administered visual analog scales to record taste intensity and hedonic ratings. Soups were given in random order, at least 3 minutes apart to allow for taste ratings and mouth rinsing, they added.
Data were analyzed using repeated measures analysis of variance. Response surface methodology (RSM) was used to determine the hedonic optima for sodium chloride and CDG, said the team.
Sweet and savoury ratings
The team found that sweetness ratings centred around 15–20 mm for most of the broths with no large deviations. However, the “ratings in terms of ‘sweet’ appear to be more parabolic where the highest ratings were at the moderate concentrations of saltiness and higher concentrations of CDG,” they added.
The authors noted that the soup rated as the sweetest was the broth that contained .33% CDG and .85% NaCl. That rated as the least sweet was that containing 0% CDG and .16% NaCl.
The broth rated as the least savoury containing 0% CDG and .16% NaCl and that rated highest being the one with .17% CDG and .85% NaCl.
The soup deemed the most pleasant was the one containing .17% CDG and .85% NaCl w/w and the soup rated the least pleasant was that with 0% CDG and .16% NaCl.
“The high concentrations of NaCl decreased the pleasant ratings to similar levels as the very low NaCl concentration, an effect somewhat modified by the CDG concentration,” noted the researchers.
They noted that the ratings for ‘liking’ were very similar to those for ‘pleasant.’ The soup rated as the most liked was the one with .17% CDG and .85% NaCl w/w and the one least liked was that containing 0% CDG and .16% NaCl.
Supplementing chicken broth with calcium di-glutamate, concluded the authors, can improve the taste profile of lower sodium soups and might be useful in reducing the salt content of the food supply.
The authors note limitations around their study, particularly the fact that it exclusively used naïve tasters rather than a mix of naïve and trained tasters but they stress that this work was building on previous research, which used similar formats.
“This feature may have led to the finding that the ‘savoury’ and ‘sweet’ ratings were correlated with the ‘liking’ and ‘pleasant’ ratings because the naïve panellists may not have been able to distinguish these specific sensations without training,” they caution.
The researchers argue that future studies on this topic should include trained testers and a wide range of food products.
Another suggested goal of additional research would be the establishment of a quantity of CDG that decreases the sensory pleasure of chicken broth “to assure that the hedonic optimum from CDG concentration is achieved.”
Source: Food Quality and Preference
Published online ahead of print: doi:10.1016/j.foodqual.2011.05.003
Title: The sensory optimum of chicken broths supplemented with calcium di-glutamate: A possibility for reducing sodium while maintaining taste
Authors: B. E. Carter, P. Monsivais, A. Drewnowski