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UM: Umami Compounds and Sodium (2013)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To examine the sensory characteristics of calcium di-glutamate (CDG) added to a low-sodium chicken broth to see if the inclusion of CDG could allow manufacturers to reduce the sodium content of foods without sacrificing palatability.

Inclusion Criteria:
  • Normal weight (BMI 18.5kg/m2 to 24.9kg/m2)
  • In good health
  • Not taking any medications that could affect sense of smell or appetite
  • Non-smokers
  • Participants completed a written consent form.
Exclusion Criteria:
  • Taking medication
  • Smokers
  • Had food allergies or restrictions
  • Disliked chicken soups or broths
  • If personal schedule did not permit regular scheduled attendance.
Description of Study Protocol:

Recruitment

Participants were recruited on the campus of the University of Washington, Seattle and the surrounding neighborhood through fliers, campus newspapers and online postings.

Design

  • Randomized crossover trial
  • The study followed a within-subject repeated-measures design, with each participant serving as his or her own control
  • Participants tasted 12 chicken broths with four different concentrations of sodium chloride (NaCl) and three different concentrations of CDG. Participants tasted all broths twice over two days and rated their taste and hedonic characteristics. Sequence was randomized.

Blinding Used

Implied for subjects: All were chicken broths.

Intervention

  • Each participant was exposed to 12 different NaCl and CDG concentration combinations of chicken broth
  • The range of CDG concentration for the broth was 0% to 0.33% w/w and the range for NaCl concentration was 0.16% to 1.7% w/w
  • The combinations of chicken broth were tested at three-minute intervals
  • Each 10ml to 12ml serving was served in 15ml cups at 50º to 60°C
  • Each participant was exposed to the 12 combinations of NaCl and CDG twice over two days, separated by at least one week.

Statistical Analysis

  • Repeated-measures analyses of variance (ANOVA) were used to analyze saltiness intensity ratings of NaCl solutions, with NaCl concentration as the repeated measure and gender as the between-subjects factor
  • Repeated-measures ANOVA were used to analyze sensory and hedonic ratings for the chicken broths, with NaCl-glutamate combinations as a within-subjects factors and gender as between-subjects factors. Bonferroni correction was applied for the sensory and hedonic responses where ANOVA's indicated a significant effect of condition
  • Sensory and hedonic ratings were then used to construct three-dimensional response surfaces for estimating sensory optima via response surface methodology (RSM)
  • Sample size calculations were based on expected largest difference in liking ratings (mm VAS) between any two conditions. The same size of 34 adults was based on a mean (±SD) effect size of eight (±23) mm and a power level of 80% and alpha=0.05, using a standard formula for crossover study designs.
Data Collection Summary:

Timing of Measurements

  • After tasting each of the 12 NaCl and CDG concentration combinations of chicken broth, participants rated the intensity of sour, bitter, salty, sweet, savory and pleasant
  • Participants were also asked to rate how much they liked each broth
  • Participants were exposed to and rated the broths twice over two days, separated by at least two weeks.

Dependent Variables

  • Sour intensity 
  • Bitter intensity 
  • Salty intensity  
  • Sweet intensity 
  • Savory intensity 
  • Savory intensity
  • Pleasant intensity
  • Liking.

All dependent variables were measured using a computer-administered visual analog scale (VAS). Participants were asked to rate the variable on a scale with opposing extremes (ie, "not at all" and "extremely"). Participants used a computer mouse to position a cursor along a 100mm line that best described their response.

Independent Variables

Each participant was exposed to 12 different NaCl/CDG concentration combinations of chicken broth:

  • 0.16% NaCl and 0% CDG
  • 0.16% NaCl and 0.17% CDG
  • 0.16% NaCl and 0.33% CDG
  • 0.53% NaCl and 0% CDG
  • 0.53% NaCl and 0.17% CDG
  • 0.53% NaCl and 0.33% CDG
  • 0.85% NaCl and 0% CDG
  • 0.85% NaCl and 0.17% CDG
  • 0.85% NaCl and 0.33% CDG
  • 1.70% NaCl and 0% CDG
  • 1.70% NaCl and 0.17% CDG
  • 1.70% NaCl and 0.33% CDG.
Description of Actual Data Sample:
  • Initial N: 34 men and women (17 males, 17 females)
  • Attrition (final N): 34 subjects
  • Age: Ranged between 20 and 35 years. Mean range was 24.2±3.8 for males and 22.8±3.5 years for females.
  • Anthropometrics: Mean BMI was 23.0±1.7kg/m2 for males and 21.6±1.9kg/m2 for females
  • Location: Seattle, Washington.
Summary of Results:

Key Findings
 

Mean (SE) Taste Intensity and Hedonic Ratings
% w/w CDG 0.16% w/w NaCl 0.53 w/w NaCl 0.85 w/w NaCl 1.70% w/w NaCl
Sour
0 20.9 (4.1)  23.7 (3.7)  20.00 (3.1)  30.8 (4.3) 
0.17 23.9 (4.2)  21.4 (3.4)  23.07 (3.3)  27.4 (4.4) 
0.33 24.7 (4.5)  21.1 (3.5)  21.20 (3.6)  25.8 (4.1) 
Bitter
0 21.7 (4.2)  22.0 (3.9)  17.8 (3.4)  22.5 (4.1) 
0.17 23.7 (3.8)  20.6 (3.6)  17.8 (3.2)  22.5 (4.0) 
0.33 28.7 (4.6)  18.5 (3.3)  17.9 (3.4)  19.8 (3.9) 
Salty
0 14.5 (2.3)  37.7 (3.5)  55.8 (3.1)  82.9 (1.7) 
0.17 16.5 (2.3)  42.9 (3.1)  54.8 (2.7)  80.9 (2.1) 
0.33 22.4 (2.8)  40.8 (3.1)  56.6 (3.2)  75.4 (2.7) 
Sweet
0 12.3 (2.3)  19.4 (3.2)  20.5 (3.4)  15.7 (3.4) 
0.17 16.4 (2.5)  24.4 (3.5)  22.5 (3.3)  17.7 (2.7) 
0.33 14.1 (2.6)  21.9 (2.9)  24.5 (3.8)  19.1 (3.5) 
Savory
0 17.8 (2.5)  39.6 (2.8)  50.7 (3.1)  46.3 (4.3) 
0.17 23.2 (2.7)  46.2 (3.1)  56.9 (3.1)  51.7 (4.1) 
0.33 27.0 (3.1)  46.9 (2.6)  57.2 (3.1)  52.2 (4.5) 
Pleasant
0 25.7 (2.6)  42.4 (2.9)  54.6 (3.1)  35.9 (3.5) 
0.17 27.3 (3.1)  50.5 (2.4)  57.8 (3.1)  41.8 (3.8) 
0.33 31.1 (2.1)  51.4 (2.9)  56.1 (2.9)  41.8 (4.4) 
Liking
0 26.4 (2.6)  46.3 (2.5)  56.8 (2.8)  37.0 (3.6) 
0.17 27.7 (2.8)  51.9 (2.0)  58.6 (2.6)  43.2 (3.7) 
0.33 29.4 (3.0)  53.1 (2.3)  55.9 (2.8)  42.3 (2.3) 
  • Sour and bitter: No significant effects of NaCl concentration or CDG concentrations
  • Salty: Significant effect of NaCl concentration, F(3,30)=253.89, P<0.001, but no effect of CDG concentration
  • Sweet: Significant effect of NaCl concentration, F(3,30)=5.94, P<0.001 and significant effect of CDG concentration, F(2,31)=3.83, P=0.03; however, no significant differences among the conditions
  • Savory: Significant effect of NaCl concentration, F(2,31)=16.13, P<0.001 and significant effect of CDG concentration, F(3,30)=41.27, P<0.001
  • Pleasant: Significant effect of NaCl concentration, F(3,30)=27.33, P<0.001 and significant effect of CDG concentration, F(2,31)=7.14, P<0.001
  • Liking: Significant effect of NaCl concentration, F(3,30)=38.26, P<0.001 and significant effect of CDG concentration, F(2,31)=3.51, P=0.04.

Other Findings

  • There were significant correlations among sweet, savory, liking and pleasant: Liking and pleasant (R=0.92, P<0.001); pleasant and savory (R=0.63, P<0.001); liking and savory (R=0.60, P<0.001); savory and sweet (R=0.34, P<0.001); pleasant and sweet (R=0.31, P<0.001); sweet and liking (R=0.30, P<0.001)
  • For all surfaces, the optimum appeared at the middle levels of NaCl (0.54% to 1.30% w/w) and the higher level of CDG (0.17% to 33% w/w)
  • For liking and pleasant, moderate liking was maintained for the lower NaCl concentrations (0.54% to 0.93% w/w) only when CDG was present.
Author Conclusion:

Supplementing chicken broth with CDG can improve the taste of lower-sodium soups and might be useful in reducing the sodium content of the food supply.

Funding Source:
Industry:
Ajinomoto Co,. Inc.
Food Company:
Reviewer Comments:
  • Relatively small sample size
  • The authors contradict themselves on page three:
    • "...[the broth rated as the most savory was] the one containing 0.17% CDG and 0.85% NaCl."
    • Later in the paragraph:
      • "The broth that was rated as the most "savory" was the broth that contained 0.33% CDG and 0.85% NaCl w/w"
    • Data in Table One are consistent with the second statement
  • Hedonic breakpoint was not well established for CDG
  • Study exclusively used naive tasters, who may not have been able to distinguish specific sensations.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? No
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? N/A
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes