EAL

UM: Umami Compounds and Palatability (2013)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine individuals' taste threshold for MSG alone and in combination with IMP-5
To examine if this threshold was related to an increase in sensory properties including pleasantness of taste and or to one's preference for dietary protein over carbohydrate and fat.

Inclusion Criteria:

Healthy, non-smoker
On no medication (except the contraceptive pill)
Not known to be allergic to MSG or other foods, not dietary restrained
Low to moderate alcohol use (up to two standard drinks per day for no more than five days per week)
BMI between 20kg/m² and 30kg/m²
Weight stable: Less than 3% change over the three months before screening
Provided written informed consent to participate.

Exclusion Criteria:

Not described.

Description of Study Protocol:

Recruitment

Responders to advertisements in a local newspaper and around the Maastricht University.

Design

Non-randomized trial; triangle taste tests.

Blinding Used

Single-blinded.

Intervention

On two separate experimental sessions at least one week apart, each subject participated in a series of single-blinded triangle taste tests to determine the taste threshold of glutamate in a clear soup when MSG alone or in combination with IMP-5 is added.

Statistical Analysis

Statistical analyses were completed using SPSS for Windows, version 11.5, and the criterion for significance (two-tailed) test was set at P<0.05
Outcomes measured on Experimental Session One were compared with those from Experimental Session Two, using Student's paired T-test
A frequency distribution of thresholds for the taste of MSG±IMP-5 was determined for the study population
Pearson's correlation and linear regression analyses were performed to examine the relationships between the threshold of MSG±IMP-5 and the change in sensory properties and protein liking eating frequency and preference scores.

Data Collection Summary:

Timing of Measurements

Two separate experimental sessions at least one week apart.

Dependent Variables

Fourteen sensory properties of the soup:
- Subjects were instructed to taste but not swallow half the volume of each soup cup and were allowed to re-taste each sample if necessary. They were asked to identify the soup with the added ingredient(s) and how certain they were about their choice.
- Another series of triangle taste tests were administered where the starting concentration of MSG was the lowest concentration previously tasted plus 0.25% IMP-5. The reason for the second series of tests was to determine if addition of 0.25% IMP-5 could lower the concentration of MSG recognized. A 10- to 15-minute break was taken between tests and subjects were instructed to rinse their mouth with water and chew on plain white bread.
- On each experimental session, subjects were required a total of between four and eight triangle taste tests to determine their taste threshold. Each experimental session took two to three hours.
Reported "liking," "eating frequency" and "preference" of 22 common high-protein, high-carbohydrate and high-fat food items assessed through questionnaire.

Independent Variables

Each subject participated in a series of single-blinded triangle taste tests to determine the taste threshold of glutamate in a clear soup when MSG alone or in combination with IMP-5 is added.

The soup stock was prepared with 20g Vectra vegetable bouillon to 1L of water and heated to about 65° Celsius
Herbs were strained from stock so that only clear broth was used for the taste tests
Manufacturer's nutritional analysis of the soup documented it as containing no glutamate
For triangle tests determining the recognition threshold of MSG alone, the concentration of MSG added to the soup ranged 0.1% to 0.8% weight of MSG per weight of soup
All concentrations of MSG and IMP-5 were within the ranges typically added to commercial food and were similar to levels of naturally occurring glutamate found in traditional dishes
Each test involved the presentation of ten rows of triplicate cups with 8ml soup (total 30 cups). Within each triplicate, either one or two cups contained soup with added MSG±IMP-5.

Description of Actual Data Sample:

Initial N: 60 subjects (36 women, 24 men)
Attrition (final N): 60 subjects (36 women, 24 men)
Age: Range 19 to 63 years
Ethnicity: Dutch
Anthropometrics: At enrollment, women had an average BMI of 23.5kg/m² and men had an average BMI of 25.9kg/m²
Location: The Netherlands.

Summary of Results:

Key Findings

Taste threshold and sensitivity of MSG was lowered from 0.33±0.24% to 0.26±0.22% when 0.25% IMP-5 was added
None of the sensory properties assessed was associated with the taste threshold of MSG and 0.25% IMP-5 in the overall study population
There was no difference between the lowest concentration of MSG alone recognized on experimental session one as compared with experimental session two (0.33±0.04 vs. 0.30±0.03; degrees of freedom=58, T=0.81; P=0.5)
There was also no difference between the lowest concentration of MSG and 0.25% IMP-5 identified on experimental session one as compared with experimental session two (0.30±0.04 vs. 0.23±0.03; degrees of freedom=53; T=1.67; P=0.1)
For the overall study population the taste threshold of MSG and 0.25% IMP-5 was not significantly associated with any of the expected sensory properties. This finding remained the same even when the non-tasters at any concentration within the 0.1% to 0.8% range were excluded from the analysis.
The taste descriptor "meatiness" was associated with the threshold data for individuals who could taste concentrations of less than 0.4% MSG
For the overall study population, the taste threshold of MSG and 0.25% IMP-5 was associated with the liking (R=0.34; P=0.01) and preference (R=0.31; P<0.02) scores for the high-protein foods.

Author Conclusion:

The study concluded that the taste threshold of MSG improves when combined with IMP-5. Moreover, the taste threshold of MSG in combination with IMP-5 was best described by the taste descriptor "meatiness" and it appears to predict the liking of and preference for high-protein foods, at least in a proportion of subjects within this population. Further investigation in a larger population of individuals is warranted to confirm these relationships.

Funding Source:

Not-for-profit

Top Institute Food and Nutrition, The Netherlands

Other non-profit:

Other:

The European DiOGenes programme 2002-2006

In-Kind support reported by Industry:

Yes

Reviewer Comments:

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?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	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?	No
	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?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	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?	Yes
	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?	Yes
	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.)	No
	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?	Yes
	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?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	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?	Yes
	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