The release of chemicals during the chewing process allows the taste buds in the oral cavity, pharynx, and larynx to transmit information for the recognition of the taste of the food. Taste is a complex sensory mechanism that can be broken down into four basic sensations (salty, sweet, sour, and bitter), but always resulting from the interaction of all of them and influenced by olfactory and trigeminal nerve mediated factors (texture, consistency, temperature, etc.).1

Changes in taste can be characterized as ageusia (absence of taste); hypogeusia (decreased perception of taste); dysgeusia (distorted taste capacity); parageusia (distorted sense of taste in the presence of stimulus); and phantogeusia (distortion of taste perception, but without the presence of stimulus).2,3 The gustatory disorders of some individuals are affected by changes in nasal–oral airflow4 during respiration that changes the influence of smell on taste. In other individuals, a decrease of saliva from chronic mouth breathing,5 which is common in childhood alters the perception of taste. Other causes of gustatory disorders include poor hygiene and impaired oral condition6 and some specific epilepsy medications.7 In children, a loss of sense of taste can cause a significant decrease in food intake possibly resulting in eating disorders, which can affect physical growth and overall development, as well as reduce the pleasure and comfort associated with food and increase the danger of food poisoning or excessive exposure to harmful environmental chemicals that would otherwise be detectable by the sense of taste.8

In order to quantify these potential difficulties and changes, different methods were developed for the evaluation of taste. The current literature9 contains several articles involving all age groups using psychophysical quantitative instruments that expose the evaluated subject to the four basic tastes. There is no major variation in the tests used to assess taste, but there are questions about their applicability in children and the effectiveness of their use specifically in that population.

Thus, this review proposes a systematic evaluation of the literature, in search of those quantitative tools used for the assessment of taste in children, documenting the frequency of use, selection criteria, and how these instruments are applied in children.

5613 studies were found with the use of the search descriptors and FTs above. Of these, 5307 were excluded by title, 248 by abstract, and 43 by full text reading. Thus, 15 articles were selected according to inclusion and exclusion criteria, but six were repeated articles, leaving nine analyzed in this review (Fig. 1).

Figure 1.

Flowchart of the number of articles found and selected after the application of inclusion and exclusion criteria.

(0.12MB).

Analyzing the selected articles (Table 1), a great diversity of studies were found. This did not allow for statistical analysis (meta-analysis), especially because the sample, the age of the population, and the objectives of the studies were varied. However, despite these differences, important insights and conclusions can be drawn from this review.

Authors belonging to the departments of medicine11–13 and nutrition14,15 are primarily responsible for the production of taste-related studies conducted on children. It is possible that the interest in these areas stems from the need to identify and determine the influence of taste in the food process, considering the impact of the gustatory discrimination and perception on feed intake – which can lead to eating disorders, which may in turn affect the physical growth and overall development of the child. Clearly, there is a lack of studies performed by phonoaudiologists, even with the considerable importance of this sense for the development of the stomatognathic functions, e.g., mastication. In this context, the need arises for an exploration of the subject by a multidisciplinary team, enabling early diagnoses and interventions in individuals who, for various reasons, present taste changes.

Studies related to the quantification of taste that focused exclusively on the pediatric population emerged in the 1980s,15 but a break occurred during a period of 10 years. From the year 2000 onwards,16 studies on this subject began to be published more frequently.6,11–14,17,18 Despite the large time lag between the moments of publication of these studies, few changes have occurred. The assessment procedures remained similar, as studies continued to be conducted with a subjective approach, showing little technological advancement in this line of research for the pediatric population. Only in 2007,13 electromyography started to be used as an adjunct tool for evaluation of the ability for perception and discrimination of tastes, demonstrating efficacy for such purpose. And recently,12 electrogustometry was used to evaluate the gustatory detection. The findings show that the chemosensory function of taste has begun to gain ground among studies of the various areas of the health sciences. However, one should bear in mind the need for greater emphasis on the development of assessment methodologies, aiming at validation and the coherent use of resources, especially in countries such as Brazil that exhibit high indices of eating problems in the pediatric population.

Australia11,13 and South Korea12,14 lead those studies related to taste in children. However, the authors also note a study6 conducted in Londrina, Paraná, Brazil. Thus, the importance given to this chemosensory function that for so long was neglected in favor of studies of other human senses is now evident. We emphasize the importance of that study which sought to establish relationships between the presence of dental caries and the perception of sweet and bitter tastes by children from different regions of that Brazilian state. Perhaps this serves as a warning that care must be taken in the provision of food to children, and the importance of oral health. According to Felicio,19 children with caries and tooth loss can decrease the intake and mastication of foods that require cutting and grinding movements, thus influencing the activity of the orofacial muscles and also exposing the indirect influence of taste in the development of the stomatognathic system and its vital functions, such as chewing, swallowing, and speaking. When he showed that quantitative tools exist to assess taste and their cost for preparation and use is reasonable, Furquim et al.6 raised questions about the low level of concern in Brazil for conducting research aimed at chemosensory functions.

The vast majority of studies we analyzed6,11,13–17 reported on populations of healthy children, possibly because there are no regulatory normative standards that allow comparisons between populations with normal development and groups of sick children. However, two studies12,18 sought to compare groups based on the presence of a taste-limiting condition. The study by Shin et al.12 highlighted the possible influence of chronic otitis media with effusion in children; and Rogers et al.18 sought to establish comparisons among children with different types of invasive developmental disorders. As to the sample size of the studies, a balance between >100 and <100 subjects evaluated was found, with a minimum of 3413 and a maximum of 43211 children. Similarly, a balance between the prevalence in the number of female6,11,13,14 and male12,15–17 children was noted in the studies analyzed. Only one study does not mention gender.18

The age range for the reviewed studies ranged from 118 to 126,11,15 years, comprising a large part of the age group defined as children by art. 2 of Law No. 8069 of July 13, 1990, which provides for the Statute of Children and Adolescents in Brazil10 that was adopted in this review. Possibly, the difference in this respect was due to the need for evidence on different aspects of child development, such as the influence of gustatory responsiveness in the process of nutrition and the consequent overall development of the child, as well as the proper establishment of oral health of children with disordered diets and exposure to foods with high levels of sugar.

The authors noted that the diversity of the populations surveyed demonstrates the importance of studies on gustation, to consider the possible negative implication of this factor on the quality of life of individuals living with complete or partial loss of their ability of gustatory discrimination. This also brings about the need to perform adjustments in the methodology employed for different population groups in terms of age, language, and cognitive and attention level, so that the instruments used are effective and efficient in determining the gustatory difficulties in children with widely varied clinical and developmental presentations. These precautions will mandate that the researcher adheres to the needs of the target audience, and thus obtain consistent results in the data presented. Also, this will allow the evaluation techniques to be reproduced for the same conditions, or with minor changes by other researchers for different situational contexts.

The selected studies had several objectives, among them: to characterize a population by means of the association among variables,6,12,14,15,18 e.g., physical growth, taste acuity, and food behaviors and preferences with the presence of dental caries;14 to compare the gustatory ability among distinct populations,6,11,12,18 e.g., Aboriginal and non-Aboriginal children11; to develop a framework for the establishment of an assessment instrument for taste16,17; and to prove the effectiveness of an electrophysiological evaluation (EMG) method as a complementary tool for identifying olfactory and gustatory changes in children.13 Despite the variety of goals, it was necessary for all studies to utilize a quantitative assessment of taste, in order to obtain results. This facilitated the establishment of standards for quantitative assessment for use with children, but with attention given to the various methods of using these patterns, as a possible strategy of adaptation of the population assessed.

In most cases, the tests and instruments used in the selected studies followed the same evaluation criteria for taste. Six studies11,14–17 used exclusively psychophysical evaluation methods composed of a standardized physical stimulus and a standardized psychological response; the children were exposed to various types of taste diluted in water and, thus, based on their gustatory perception, responses were elicited. Some studies sought answers regarding the detection of taste,6,14–17 as to the pleasantness13,16 and preference;17 others sought information about gustatory discrimination.11,12,15 This reveals a possible method to be developed in pursuit of the standardization of quantitative instruments for taste assessment in children aged from zero to 12 years.

However, three studies used different methodologies.12,13,18 The electrogustometer, a device that provides quantitative gustatory detection thresholds by means of the application of an electric current in four areas of the tongue (tip, base, and sides), registering the minimum voltage that allows the individual being evaluated to perceive a metallic or sour taste, was used with the aim of evaluating the changes in taste thresholds in children with chronic otitis media with effusion, relating these findings to body mass index.12 Electromyography, besides representing a psychophysical test, was used as an accessory and as a computerized control for the movement of specific facial muscles of individuals exposed to pleasant (sweet) and unpleasant (bitter) tastes.13 Finally, one study established scores from zero to 4 points through a sensory profile questionnaire of patients with autistic spectrum disorders, through the responses of the children's parents.18

To facilitate standardization of the instruments used, exposure to water immediately after each taste sample offered, a procedure known as rinsing was used in all the studies that adopted a psychophysical test methodology.6,11–17 In these same studies, the number of samples varied between 315 and 1316 for each evaluated taste. However, the number of samples increased proportionally to the decrease in tastes evaluated. Thus, there was a trend for the presentation of three,15 four,12 or five11,17 samples when assessing the four basic tastes (sweet, salty, sour, and bitter), and an increase in the number of samples when only two distinct tastes were tested.13,14,16 Some studies6,11,14,16,17 reported that these samples were increasingly concentrated, representing a method to establish a score for the test through the minimum threshold of detection of the solution.

In addition, there was an agreement on the choice of the evaluated tastes, considering that the studies used two6,13,14,16 or more11,12,15,17 psychophysical tests for the four basic tastes, and some studies15,16 have chosen to provide alternatives, such as solutions with water and a specific taste. One study17 reported that the application time for the entire test was approximately 15min; another study11 related that the interval between the exposure of one taste sample to the subsequent taste was 20–30s. The method of application of the solutions ranged from the application of the solution on the surface of the tongue6 to drinking the food solution.17

In most of the studies we analyzed,6,11–16 the scoring process was based on the minimum threshold of detection6,12,14–16 and discrimination13,15,16 of concentration. For a study11 that evaluated only the gustatory discrimination, the authors considered the presence of a “taste disorder” when three errors occurred after the subject was exposed to five concentrations of each taste in the evaluation; and Horn, Jusic, Sapunar, and Milanovic (1980)15 found hypogeusia (decreased gustatory acuity) when detection or discrimination errors occurred in three concentrations of the same taste.

As for the child population, some studies adopted representative figures to aid in taste identification11 and pleasantness;16 other investigations adopted a children's story to contextualize the test conducted,16 a time prior to the test to familiarize with solutions,6 and guidelines prior to individual evaluation.14 These performed adaptations possibly involve the particularities presented by the child population, such as cognitive, linguistic, and emotional development, and different levels of attention and concentration that should be factors addressed when designing evaluative instruments specific to this age group. Thus, some changes possibly occur to adapt the conditions of an evaluative methodology to the age of the population.

In the description of the evaluative methodologies used, it was noted that there are already several common points in the instruments used for taste evaluation, and a few points were referred as disagreements or not clarified by research. Still, the various techniques may generate questions about their effectiveness, considering the existence of some discrepancies. But it must be considered that, for each population group, some adjustments always will need to be made.

Thus, it is pretentious to make comparisons or judgments of techniques, classifying them as better or worse, for use in children. Each technique must have a globally established foundation. However, modifications should be made, in an attempt to consider the specific needs of each sample population. This premise will be decisive in the choice of the test(s) used and in modifications to be made, but it is also necessary to consider that, for different systems and health facilities in countries and states with sometimes conflicting conditions, some choices made or changes desired may not be implemented. But possibly, this will not be detrimental for localities with less favored socioeconomic status, since both instruments easily reproduced in compounding pharmacies at low cost and high-tech equipment are now used.

Finally, as to the results, most of them had their hypotheses confirmed.6,11–13,15–18 Only one study did not confirm the initial hypothesis, finding no statistically significant association between the presence of dental plaque and the acuity of taste, but another study14 established the relationship between the presence of dental caries and the high level of perception of sweet taste.6 In addition, greater difficulty of children in the perception of sweet taste was noted in some studies11,12 who performed this survey by offering such stimulus. Attention must be drawn to the results of two studies16,17 that proposed to develop quantitative taste assessments. These studies confirmed that it is possible and feasible to conduct these tests in children, provided that they are relevant to the conditions and needs required by the specific age group. Therefore, the importance of early investigation of gustatory conditions through reliable means of diagnosis should be emphasized. The authors suggest conducting studies for validation of quantitative taste assessment tools to use in pediatric populations with typical and atypical development.

With the advancement of research and the interest of many professionals involved in the function of taste (speech therapists, nutritionists, otorhinolaryngologists, neurologists, occupational therapists, and dentists), we are achieving good results – especially regarding standardization of quantitative tests that are appropriate and age-specific.

This review showed that, although there are still some differences and little information on some specific points (such as the duration of the test and the time between each sample) and some technological increments in the evaluation of taste, the psychophysical tests for quantitative evaluation of this function already follow the standard criteria of choice regarding the methodology applied (presentation and chosen gustatory stimuli, presentation and quantity of samples by taste, use of the rinsing method) and the scoring modality adopted.

Therefore, the findings in this study enable greater reliability for future research, employing similar methodologies and based on published studies for assessment of gustatory function. Furthermore, this methodology can be applied with reliability in the phonoaudiological rehabilitation of children with disorders of taste.

This study was supported by FACEPE 2012 (Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco) and CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), Process: 475641/2011-6.

The authors declare no conflicts of interest.