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Taste Preference and Rating of Commercial and Natural Thickeners
Dysphagia can negatively affect quality of life, nutritional status, and pulmonary status of individuals. The most common intervention for dysphagia is the use of thickening agents for liquids. This group study (n = 43) investigated the taste preference, taste ratings, and ranking for nectar-thick hot and cold beverages using three types of thickeners: SimplyThick™, Thick-It®, and noncommercially prepared natural thickeners. Results demonstrated a significant difference between the taste ratings of two commercial thickeners and between one commercial and the natural thickener for the ranking of taste with hot beverages. Every participant rated at least one of the thickener beverages as having an acceptable taste for the hot chocolate and fruit juice beverages. Exploring individual preferences is critical to selecting a beverage that increases compliance to clinical recommendations.
Dysphagia can negatively affect quality of life (QOL), nutritional status, and pulmonary status of individuals. Previous research has documented that patients with often reported dysphagia had undermined their health and QOL. Ekberg, Hanley, Woisard, Wuttge-Hannig, and Ortega (2002) performed a study with 360 participants from the United Kingdom, France, Spain, and Germany. Eighty-four percent of the participants with dysphagia thought that eating should be an enjoyable experience, but only 45% considered it so because of the problems associated with dysphagia. The management of swallowing impairments includes using thickened liquids to achieve a safe swallow. Thickening liquids is the most frequently used compensatory intervention for dysphagia implemented in hospitals, rehabilitation centers, and long-term care facilities (Castellanos, Butler, Gluch, & Burke, 2004; Feinberg, Knebl, Tully, & Segall, 1990). In general, the goals of a dysphagia diet are for the patient to maintain adequate nutrition, safe oral intake, and gratification (Glassburn & Deem, 1998; Martin, 1991; Penman & Thomson, 1998).
Often what affects QOL is not only the physical struggle but also the alteration of preferred food selections in normal diets. Despite the intended health benefits, patients may object and refuse to comply if their diets are altered to include thickened liquids. Rejection of thickened fluids can lead to dehydration and related health problems (Ekberg et al., 2002; Penman & Thomson, 1998).
A reason for noncompliance with thickened liquids may be the changes in taste perception. Systemic diseases and medications can cause alterations in taste and smell (Ship, 1998). Taste perception may also be affected by changes in taste bud cell responses (Fukunaga, Uematsu, & Sugimoto, 2005) and olfactory sensitivity (Murphy, Cain, Gilmore, & Skinner, 1991; Ship, 1998) in aging. Individuals at risk for dysphagia are often the same individuals who already are affected by other factors that change taste and smell.
The population group that experiences dysphagia includes children and adults with neurological disorders. These individuals may have impaired sensory motor systems. Taste buds are found in the tongue, palate, and pharynx. The sensory system of taste involves nerve fibers from the facial, glossopharyngeal, and vagus nerves (Nolte, 2002). Sensory information from the tongue also results in secondary taste fibers, the nucleus being the pontine taste area, and projects to the thalamus. Another at-risk population for dysphagia comprises those with head and neck cancers. For these individuals, sensory decline may exist because of the surgical outcomes, radiation, or chemotherapy. Surgery can involve the sensory motor system, either in direct removal of oral or pharyngeal tissue or in severing of the sensory nerve pathway. Head and neck cancer treatments with chemotherapy or radiotherapy have been shown to affect olfactory and taste cells (Rose-Ped et al., 2002; Schwartz, Weiffenbach, Valdez, & Fox, 1993; Wickham et al., 1999).
Providing a safe dysphagia diet with acceptable taste is important in maximizing the patient’s compliance to the recommended diet and improving QOL (Pelletier, 1997). The importance of taste needs to be considered when a liquid thickening agent is chosen. The sensory qualities of liquids, such as flavor, texture, and aroma, are important factors that can also affect taste and influence whether the thickened liquids are accepted (Pelletier, 1997). Using creative substitutes as thickeners may enhance the taste of the beverage and the overall acceptance of thickened liquids (Blades, 2001). A multidisciplinary team of nurses, dietitians, speech language pathologists, and occupational therapists can participate in evaluating the patient’s acceptability of the taste of thickened liquids.
Pelletier published a study in 1997 comparing five commercial thickening agents: Thick-It® (Milani Foods), Thicken Right™ (Menu Magic), Thick & Easy™ (American Institutional Products), Thicken Up® (Sandoz Nutrition) and Quik Thick™ (Gage Food Products) with apple juice, 2% milk, and black coffee at three thickness levels. Pelletier found that Thick It and Thicken Right had better taste than the others with the juice for syrup and honey consistencies. Pelletier also concluded that consistency and taste are dependent on the time period that the drink sat, liquid type, and desired thickness. Researchers have suggested the need for investigation of the use of natural thickeners (Castellanos et al., 2004; Pelletier, 1997).
The aim of the current study was to investigate whether there was a significant difference between the taste of two commonly used commercial thickeners, SimplyThick™ and Thick-It, versus the substitutions, which are referred to as natural thickeners. It was proposed that the natural thickeners would be preferred over the commercial thickeners on the basis of taste.
The purposes of this study were (a) to determine whether there was a taste preference between three types of thickeners: SimplyThick, Thick-It, and a natural thickener, (b) to determine the taste rating of the thickened beverages, (c) to determine the overall acceptability of the thickened beverages, (d) to determine the ranking of the thickened beverages based on a scale from most preferable to least preferable, and (e) to determine the characteristics of the beverages ranked as not preferable.
Methods and Procedures
Participants were recruited from a university medical center and allied health college. The study did not limit age during the recruitment process because dysphagia affects people of all ages. This study targeted normal healthy adults to provide baseline research data of acceptability of thickened liquids. Forty-three participants, ranging in age from 20 to 41 years, participated in the taste test. Mean subject age was 26 years, and 38 were female and 5 male. Before participation, each participant answered a questionnaire to establish his or her eligibility. Documentation of any food allergies, dysnosmia, dysphagia, special diet needs, and abnormal oral motor deficits resulted in disqualification from the study.
The two beverages thickened were Juicy Juice® fruit juice and Nestlé’s Hot Chocolate®. The two commercial brand thickeners were Thick It and SimplyThick. The two natural thickeners were Wilderness Raspberry Applesauce®, and JELL-O® Brand Chocolate Pudding and Pie Filling. Thick-It and SimplyThick are commercial products usually purchased at a drug store. Thick-It was chosen because a previous study identified it to be superior in taste when compared to Quick Thick, Thicken Up, and Thick & Easy commercial brands (Pelletier, 1997). Simply Thick was chosen because it is a gel-based thickener and is relatively new on the market. Premeasured individual packets of Thick-It and SimplyThick were used for nectar consistency, which eliminated potential measuring error. Nectar consistency for thickness was selected for two reasons: (a) being sold more frequently than other consistencies (L. Berger, personal communication, February 24, 2003; M. Knehans, personal communication, March 21, 2003), and (b) research evidence in a recent study of 252 facilities that 60% of those residents received thickened liquids of nectar consistency (Castellanos et al., 2004).
SimplyThick is a gel product used to thicken hot or cold liquids. SimplyThick is made from water, xanthan gum, citric acid, sodium benzonate, and potassium sorbate by Phagia-Gel Technologies. Phagia-Gel Technologies claims that SimplyThick is flavorless, does not alter taste, and increases patient acceptance (M. Knehans, personal communication, March 21, 2003). Phagia-Gel Technologies beverages are ready to drink as soon as mixing is completed. Beverage thickness is stable and consistent, whether hot, cold, frozen, or thawed, with no additional thickening or separation over time. SimplyThick is packaged for individual usage, which eliminates measuring and reportedly ensures consistent thickness and simplified training for patients and caregivers. SimplyThick is packaged in nectar and honey consistencies and is designed for use in a 4-oz serving. For pudding consistency, the use of two honey packets is required for a 4-oz serving.
Thick-It is a powdered product used to thicken hot or cold beverages or foods to obtain any level of consistency. Thick-It is made of modified cornstarch and maltodextrin by Precision Foods. Precision Foods claims that Thick-It maintains good consistency within the different viscosity levels now defined by the National Dysphagia Diet. It comes in 8-oz cans and in individual serving packages for nectar consistency.
The noncommercially prepared natural thickeners were created by using foods available in most grocery stores. Applesauce was used to thicken the fruit juice. Chocolate pudding and pie filling was used to thicken the hot chocolate.
The study was conducted in a food laboratory equipped with a room designed for taste testing experiments. The two beverages—fruit juice and hot chocolate—were thickened with the three types of thickeners. Thick-It and SimplyThick were mixed with the beverages as prescribed by the manufacturer’s directions. Two certified speech-language pathologists, one speech pathology graduate student, and a registered dietitian collaborated for the creation of the standardized recipes with natural thickeners (see Tables 1 and 2). Multiple trials using the natural thickeners were conducted to ensure an acceptable taste and a comparable thickness to the commercial thickeners. Thickness was determined using professional judgments, similar to clinical practice.
All beverages were prepared and served immediately. The beverages were presented randomly and random numbers were assigned to each thickened beverage. Each cup contained 4 oz of each sample. Disposable lids that had tabs to drink through were used with the cups, so that the appearance of the beverage did not influence judgment. The thickened fruit juice beverages were presented first, followed by the hot chocolate beverages. Each thickened fruit juice beverage was presented and rated individually on a five-point scale; see Table 3. Water was provided between each sample of fruit juice beverage. After all three thickened samples of the fruit juice beverages were individually rated, the participants were asked to rank the three samples of the thickened fruit juice beverage from most preferable to least preferable. Then the participants were asked to identify characteristics of the beverage selected as least preferable (see Table 3). This process was repeated for the hot chocolate. The participants were provided a form to fill out their responses.
A statistical team used the Statistical Package for Social Sciences (SPSS-Version 10) software to analyze the results using an analysis of variance. Analyses were performed for the two dependent variables, rating and ranking of the taste of the three types of thickeners.
Taste Rating of Beverages
The taste ratings of the fruit juice and hot chocolate were based on a 5-point scale (1 = great taste, 2 = good taste, 3 = fair taste, 4 = poor taste, 5 = extremely poor taste) for the three thickeners (see Figures 1 and 2). There was no significant difference for rating (F = .088, p > .05) of taste for the fruit juice beverages (see Figure 1). There was a significant difference between Simply Thick and Thick-It for the rating (F = –.83, p < .05) of taste for the hot chocolate beverages (see Figure 2).
Overall Acceptability of Thickeners
The overall acceptance of fruit juice and hot chocolate for the three types of thickeners was determined using the 5-point rating scale. A response of 1–3 indicated that the subject would drink the beverage and was defined as acceptable. (A rating of 4–5 indicated that the subject would not want to drink that beverage, and was defined as unacceptable.) Of the thickened fruit juice beverages, the naturally thickened had the highest taste acceptance, with 79% of participants selecting a rating of 1–3. The SimplyThick fruit juice was second for taste acceptance, with 76% of participants selecting a rating of 1–3, followed by the Thick-It fruit juice with 74%. The SimplyThick hot chocolate beverage had the highest taste acceptance across all beverages with 93% of participants selecting a rating of 1–3. The natural hot chocolate beverage was selected by 76% of the participants as an acceptable drink. The Thick-It hot chocolate beverage had the lowest taste acceptance across all beverages; 71% of participants rated it as acceptable.
Ranking of Beverages
Taste rankings, displayed by the percentages of preference (most preferable to least preferable) for cold beverages (fruit juice) and hot beverages (hot chocolate), are shown in Figure 3. There was no significant difference for the ranking of the fruit juice beverages (F = .457, p > .05).
A significant difference was detected between the taste rankings of SimplyThick and Thick-It® (F = –.76, p < .05) for the hot chocolate. There was also a significant difference between the natural thickener and Thick-It for the taste ranking (F = –.52, p < .05) of the hot chocolate. SimplyThick and the natural thickener were found to be preferred over Thick-It for the hot chocolate beverages. The ranking preference (most to least) for the hot chocolate beverages were SimplyThick, natural thickener, and Thick-It.
Characteristics of Beverages Ranked as Least Preferable
After participants ranked the beverages from most to least preferable, they were asked what characteristics made the beverage least preferable. The participants could choose from the following characteristics: lumpy, smooth, too thick, gritty, bland, bitter, sour, not sweet enough, too sweet, and other. Researchers charted the top three characteristics of the fruit juice beverages (Figure 4) and the hot chocolate beverages (Figure 5) that were ranked as least preferable. The perceived characteristics of the naturally thickened fruit juice were that it was gritty, too thick, and lumpy. The perceived characteristics of the SimplyThick fruit juice were that it was not sweet enough, bland, and other. Some comments in the other category were that it was too smooth and slimy, and that it did not have much taste. The perceived characteristics of the Thick-It fruit juice were that it was not sweet enough, bland, and too thick (see Figure 4). The perceived characteristics of the natural hot chocolate were that it was too sweet, not sweet enough, and the other category (see Figure 5). Some comments were that there was a strong aftertaste, there was too much flavor, and it was too buttery. The perceived characteristics of the SimplyThick hot chocolate were that it was bland, not sweet enough, and the other category. The perceived characteristics of the Thick-It were that it was not sweet enough, too thick, and the other category. Some comments were that it was difficult to swallow, was too much like a milkshake, and did not taste like chocolate, and that the thickness took away from the taste.
Producing an acceptable taste is an important consideration when recommending thickened liquids. The current study investigated whether two commercial thickeners, SimplyThick and Thick-It, and two noncommercially prepared natural thickeners, applesauce and chocolate pudding and pie filling, affected taste differently. Significant differences in taste were detected among the hot chocolate beverages. SimplyThick and the natural thickener were found to be superior on the basis of taste to Thick-It.
No significant differences were found for ratings of taste among the three thickened fruit juice beverages. The data suggest that all the fruit juice beverages had a high acceptance rating. That significant taste differences were not detected among the cold beverages but were detected among the hot beverages indicates there might be a relationship between temperature and taste. Further studies testing thickened hot and cold beverages may help determine whether temperature and taste influence the acceptability of thickened liquids.
There was a difference of perceived thickness and taste between SimplyThick and Thick-It. The characteristic of being “too thick” was the most frequent response in the perception of the Thick-It hot chocolate. No participant described SimplyThick hot chocolate as too thick. The influence of perceived thickness on ratings of taste was not evaluated in this study, but warrants further investigation. Toward that effort, it is important to ensure consistency of beverage viscosity across thickening agent types. Standardized beverage viscosities across conditions (agent, preparation method, etc.) can ensure that the most desirable and safest beverage for patient consumption is offered (Robbins et al., n.d; Giel & Felt-Gunderson, 1997).
The most encouraging finding from this study was the fact that all participants perceived at least one beverage as acceptable, or rated at least “fair.” At the outset of this study it was proposed that a noncommercial natural thickener would be preferred over two commercially available thickening agents. The results did not support this assumption for the fruit juice. The juice was equally acceptable for the natural and commercial thickeners. In the case of hot chocolate, both the gel-based and natural thickener were preferred to the powdered product, Thick-It, based on taste.
Limitations of the Study
Further studies are suggested to test long-term acceptance of thickened liquids across varied populations. Cultural, gender and age differences should be investigated by using group studies. This study comprised 43 participants but did not specify for race, gender, or age. Research should also compare taste and preference of thickened liquids by participants with health issues and/or swallowing disorders.
This study investigated one thickness level for liquids. The Pelletier study (1997) included only four participants for judges, yet the number of beverages and thickness levels were greater. Neither the Pelletier nor the current study researched the taste perception and acceptability of the liquids over time. For example, initial response may be that the liquid was acceptable, but if consumed on a daily basis, the response may differ. In addition, the liquids tested were both sweet. Additional research could involve a variety of flavors.
Implications for Practice
In clinical practice there is a need to increase the appeal of thickened liquids because diet modifications continue to be a common intervention for patients with dysphagia. For hot beverages (hot chocolate), results of the current study suggest the use of natural thickeners may help the general appeal of drinking thickened liquids. Use of a natural thickener may be more economical and convenient. However, there are no recipes using natural thickeners that have been standardized for viscosity nor thickness. Lack of standardized viscosities is problematic across commercially prepared and noncommercially prepared thickening agents (Robbins et al., n.d.; Cichero, Jackson, Halley, & Murdoch, 2000). Even method of mixing can influence viscosity measures. Rehabilitation nurses or clinicians would need to be trained to obtain a level of thickness recommended for the diet. The advantage of a commercial thickener is that it provides instructions on individual packets for each consistency. The individual packets help create the recommended thickness and are convenient for everyday use.
This study shows the importance of trying different thickening agents with different beverages to attain the most satisfying combination for patient acceptance. In the rehabilitation setting, nurses identify patients who reject thickened liquids. Rehabilitation nurses, dietitians, occupational therapists or speech language pathologists can all participate in the assessment of the patient’s acceptance of different products. Too often, patients are asked to sign noncompliance forms after they refuse a trial of one brand of thickener. The authors advise that the team offer several options, commercially or naturally thickened liquids, before reaching a determination of noncompliance. Naturally thick liquids, which are easily found in grocery stores, are nectar juices, yogurt, buttermilk, and smoothies. These products are also available institutionally through food distributors.
This study supports the suggestions of Castellanos et al. (2004) and Pelletier (1997) that additional research on naturally thick beverages is needed. Based on the results of this study, consideration should be given to using different types of thickeners in the clinical setting to help increase patient satisfaction, nutritional status, and compliance with the recommended diet.
The authors would like to acknowledge Phagia-Gel Technologies (Simply Thick) and Precision Foods (Thick-It) for product contributions.
This study was granted approval for exempt status by the University of Cincinnati Institutional Review Board—Social and Behavioral Sciences (IRB #03-02-14-01X).
About the Authors
Melissa Horwarth, MA CCC-SLP, is a speech language pathologist at the Hearing Speech and Deaf Center of Greater Cincinnati, Cincinnati, OH.
Angel Ball, PhD CCC-SLP, is an assistant professor and speech language pathologist in the University of Cincinnati Department of Communication Sciences and Disorders, Cincinnati, OH.
Rebecca Smith, MEd RD, is an assistant professor and dietitian in the University of Cincinnati Department of Nutritional Sciences, Cincinnati, OH.
Direct correspondence to Angel Ball, PhD CCC-SLP, Department of Communication Sciences and Disorders, University of Cincinnati, 3202 Eden Avenue ML0379, Cincinnati, OH 45267-0379, or via e-mail to firstname.lastname@example.org
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