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Reduction of added salt levels in soups is recommended. We evaluated the impact of a 30% reduction of usual added salt in vegetable soups on elderly and children's saltiness and liking evaluation.
Subjects were elderly and recruited from two public nursing homes (29 older adults, 79.7±8.9 years), and preschool children recruited from a public preschool (49 children, 4.5±1.3 years). This study took place in institutional lunchrooms. Through randomization and crossover, the subjects participated in two sensory evaluation sessions, on consecutive days, to assess perceived saltiness intensity (elderly sample) and liking (elderly and children samples) of a vegetable soup with baseline salt content and with a 30% salt reduction. Elderly rated perceived liking through a 10 cm visual analogue scale [‘like extremely’ (1) to ‘dislike extremely’ (10)] and children through a five-point facial scale [‘dislike very much’ (1) to ‘like very much’ (5)].
After 30% added salt reduction in vegetable soup, there were no significant differences in saltiness noted by the elderly (
A 30% salt reduction in vegetable soup may be achieved without compromising perceived saltiness and liking in children and the elderly.
High sodium intake has been associated with the etiology and pathogenesis of hypertension (
The World Health Organization (WHO) recommends the consumption of less than 2,000 mg sodium per day for adults and the adjustment of 2,000 mg sodium downward based on the energy requirements of children (
Since most sodium is consumed in the form of sodium chloride, which is table salt (approximately 40% sodium), the European Salt Framework established a benchmark of a minimum of 16% salt reduction over 4 years for all food products, also encompassing salt consumed in restaurants and catering, including vegetable soup (
Thus, the objective of this study was to assess the perceived saltiness intensity and liking of a vegetable soup after 30% reduction of the usual sodium content, in a sample of institutionalized elderly and community preschool children.
Elderly subjects (
All children from a public preschool were also invited to participate (
Each set of participants – elderly and children – was randomly divided into one of two groups to perform the saltiness and liking evaluation of vegetable soups in two sessions on separated days.
Each group tasted and evaluated the soups following a crossover design, in which the subjects were randomly assigned to two different arms of the study, one consuming a vegetable soup with baseline sodium content and the other having the soup with 30% salt reduction, switching the soups with the two different levels of sodium content afterwards. Other ingredients in the soups besides salt were the same in both groups. The study was also single blinded such that the subjects were unaware of the salt content of the soup they were assessing.
The sensory evaluation took place in the usual lunchrooms at the institutions, in order to minimize the effects due to changes in the physical environment, and at the typical lunch period – between 12:00 and 13:00 am – which is also the time when participants are most alert to perform sensory testing. Furthermore, the researchers visited the institutions several times before the test so that participants became familiar with them.
According to our previous experiences (
To estimate baseline sodium content, four samples of soup were collected, two samples before adding salt in confection by a food handler and two samples after added salt, in each day. Baseline added salt was calculated subtracting average sodium before adding salt (sodium from vegetables) to average sodium after added salt, and the average sodium content of the 7 days/5 days was considered as the baseline.
Sodium content was determined using flame photometry method, the intern reference method to analyze sodium in food matrices (
For sensory evaluation, the vegetable soups were presented in a white ceramic plate at 68–72°C. Soups were served with nectar consistency and stored in the first day for the second refrigerated at 4°C, without added salt. Before the test soups were heated, soups were divided in two groups: in one group, the amount of added salt corresponded to the usual amount in baseline soups, and in the other group of soups, the amount of added salt was reduced by 30% compared to baseline. For the vegetable soups prepared for the elderly, a traditional recipe was selected, consisting of 1.5 kg of potatoes, 2.0 kg of white cabbage, 1.5 kg of Portuguese cabbage, 0.5 kg of onions, and 1.0 kg of carrots. For preschool children, the usual recipe for the soup was prepared with 7.0 kg of potatoes, 1.3 kg of onions, 2.3 kg of carrots, 2.5 kg of leek, and 30 g of garlic.
A sensory description of the two soups with the two different sodium contents was performed; elderly evaluated saltiness and liking using a visual analogue scale (VAS) with 10 cm line scale [from ‘extremely’ (1) to ‘not at all’ (10) for salt perception and ‘like extremely’ (1) to ‘dislike extremely’ (10) for hedonic perception], and children evaluated liking through perceived liking ranking using a five-point facial scale (FS), by means of smiles icons that express feelings from ‘dislike very much’ (1) to ‘like very much’ (5). Given the low educational attainment in the elderly, a prior explanation of how to fulfill the VAS was given by a trained researcher.
A questionnaire was applied to elderly and to the children's parents in order to collect data on age, and the highest education qualification completed. Weight and height measurements were performed in the elderly using standardized procedures (
Mean and standard deviations (SD) were used to describe continuous variables with normal distribution; otherwise, medians, minimum and maximum were presented.
Data analysis was performed with SPSS (version 17, Chicago, IL). The Shapiro–Wilk test was used to assess the assumption of normality, as VAS and FS variables did not reach normality, its median scores were compared using a non-parametric test for paired data, the Wilcoxon signed rank test. Spearman correlation coefficient was used to measure the degree of the association between pairs of variables. A
The impact of reduced added salt level on sensory evaluation is described separately for children and elderly.
Elderly subjects (
The baseline sodium concentrations in soups from each institution are shown in
Sodium content in vegetable soups (mg sodium/100 g soup)a
| Before adding salt | After adding salt | Salt added during the cooking process | |||||||||||
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| Mean±SD | Med | Min | Max | Mean±SD | Med | Min | Max | Mean±SD | Med | Min | Max | ||
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| NH1 | Soup day 1 | 4.5±0.1 | 212.4±4.6 | 207.9±4.5 | |||||||||
| Soup day 2 | 5.5±1.6 | 315.2±23.7 | 309.7±22.1 | ||||||||||
| Soup day 3 | 1.3±1.2 | 290.8±12.2 | 289.5±11 | ||||||||||
| Soup day 4 | 5.5±1.5 | 308.3±11.4 | 302.8±9.9 | ||||||||||
| Soup day 5 | 17.2±2.6 | 334.4±1.9 | 317.2±0.7 | ||||||||||
| Soup day 6 | 7.4±4.2 | 267.8±12.3 | 260.4±8.1 | ||||||||||
| Soup day 7 | 2.7±0.8 | 420.0±12.3 | 417.3±11.5 | ||||||||||
| Mean of the 7 days soups | 6.3±4.6 | 4.6 | 1.3 | 17.2 | 307.0±11.2 | 308.3 | 212.4 | 420.0 | 300.7±6.6b | 302.8 | 207.9 | 417.3 | |
| NH2 | Soup day 1 | 2.4±0.6 | 358.1±10.2 | 355.7±9.6 | |||||||||
| Soup day 2 | 13.5±2.9 | 185.4±4.1 | 171.9±1.2 | ||||||||||
| Soup day 3 | 33.9±2.0 | 166.4±10.2 | 132.5±8.2 | ||||||||||
| Soup day 4 | 18.9±0.2 | 175.3±14.2 | 156.4±14.0 | ||||||||||
| Soup day 5 | 21.4±1.3 | 204.9±5.0 | 183.5±3.7 | ||||||||||
| Soup day 6 | 130.1±1.0 | 300.9±6.5 | 170.9±5.5 | ||||||||||
| Soup day 7 | 0.6±0.4 | 226.9±9.1 | 226.3±8.7 | ||||||||||
| Mean of the 7 days soup | 31.5±6.2 | 15.7 | 0.6 | 130.1 | 231.1±13.5 | 212.5 | 166.4 | 300.9 | 206.7±7.3b | 196.8 | 132.5 | 355.7 | |
| PS | Soup day 1 | 3.0±1.1 | 164.6±3.5 | 161.6±2.4 | |||||||||
| Soup day 2 | 3.0±0.5 | 107.6±2.9 | 104.6±2.5 | ||||||||||
| Soup day 3 | 3.0±0.5 | 110.2±8.4 | 107.2±8.0 | ||||||||||
| Soup day 4 | 18.5±0.9 | 67.2±5.9 | 48.7±5.0 | ||||||||||
| Soup day 5 | 18.5±0.9 | 318.0±19.5 | 299.5±18.6 | ||||||||||
| Mean of the 5 days soup | 9.2±0.7 | 6.1 | 3.0 | 18.5 | 153.5±8.0 | 131.9 | 67.2 | 318.0 | 144.3±7.3b | 125.8 | 48.7 | 299.5 | |
aSodium obtained using flame photometry methodology; vegetable soups included four vegetables and potatoes.
bValues used to perform a 30% salt reduction.
SD=standard deviation; Med=median; Min=minimum; Max=maximum; NH1= Nursing Home 1; NH2= Nursing Home 2; and PS= preschool.
The sensory evaluation of the two soups (one with baseline salt content and another with 30% added salt reduction) is presented in
Evaluation tests according to the salt content in the soup (hedonic and perceived salt ratings)
| Vegetable soups with usual added salt | Vegetable soups with 30% reduction of added salt | |||||
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| Hedonic perception | Mean±SD | Median (Min; Max) | Mean±SD | Median (Min; Max) |
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| Elderly ( |
Saltiness | 5.7±3.2 | 5.0 (3.4; 9.1) | 6.9±2.5 | 7.8 (4.9; 9.3) | 0.150 |
| Liking | 2.1±2.8 | 0.8 (0.2; 2.7) | 2.2±2.9 | 0.7 (0.3; 4.0) | 0.860 | |
| Preschool children ( |
Liking | 4.4±0.5 | 4.0 (4.0; 5.0) | 4.41±0.54 | 4.0 (4.0; 5.0) | 0.160 |
SD=standard deviation; Min=minimum; Max=maximum.
The overweight and obesity prevalence values found in the elderly and children samples were similar to values reported in the same age groups in Portugal (
A 30% added salt reduction did not change the saltiness and liking perception of a vegetable soup in both preschool children and elderly subjects. These results encourage for achieving higher sodium reductions than those typically advised, namely with decreases between 4 and 10% per year (
Strong concerns about the consumption of salt in vegetable soup exist in Portugal. The soups analyzed to establish the baseline (7 days in institutionalized elderly and 5 days for preschool children) take part in the usual menu cycle in both institutions, and regardless of the recipe, they are usually composed of four vegetables plus potatoes. Thus, the soup used in the trial symbolizes a general traditional vegetable composition of any of the soups analyzed in the baseline, with no expected significant variations in the nutritional composition, other than added sodium. The latter may vary according to the food handlers/cookers since no standardized amount of added sodium is established for each recipe.
Accordingly, in our study, salt added in soups during the cooking process (
According to a study that evaluated the sodium content of Portuguese vegetable soups in NH, elementary schools and kindergartens, subjects eating two portions of soup per day may reach 67% of the upper limit of sodium intake, when considering the mean values of sodium in vegetable soups (
Salt is used in the food industry and during the cooking process due to its capacity to improve sensory properties of food (
Few studies have assessed the impact of a reduction of the sodium content of vegetable soup on hedonic perception of consumers in different age groups. Drewnowski et al. (
The results of the present study should be interpreted while taking into account its strengths and limitations. The study was carried out in the habitual familiar context for participants and during the period that they usually take their meals, leaving these variables constant over the intervention. Another strength of the study was the use of a single-blinded crossover model. On the other hand, participants were institutionalized; that is, the cooking process was the responsibility of the institution. Thus, the results should not be speculated to other population groups, neither the food used to taste stimuli; the perception of sodium reduction in vegetable soup should not be generalized to other foods because the effect of salt appears to be food specific. Another limitation of this study is that salt reduction was carried out a particular kind of vegetable soup recipe; however, we can achieve other values of reduction of salt content in other types of vegetable soup with other ingredients without affecting saltiness and hedonic perception.
For that reason, in the future, it will be important to consider other vegetable ingredients and recipes, and other values for the reduction of added salt in order to formulate targeted measures to control sodium intake, and set realistic and culturally relevant goals in food policy.
In conclusion, a 30% salt reduction in soups can be achieved without affecting perceived saltiness intensity and liking among the elderly and children, considering the reported mean baseline content of sodium.
The authors declare no conflict of interest.