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Intensification of Sensory Properties of Foods for the Elderly¹

Department of Psychiatry, Duke University Medical Center, Durham, NC 27710

	ABSTRACT

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Taste and smell losses in the elderly can reduce appetite and lead to inadequate dietary intake. Although these chemosensory deficits are generally not reversible, sensory interventions including intensification of taste and odor can compensate for perceptual losses. One method for "treatment" of chemosensory losses involves sensory enhancement of foods with flavors and monosodium glutamate (MSG). Amplification of flavor and taste can improve food palatability and acceptance, increase salivary flow and immunity, and reduce oral complaints in both sick and healthy elderly.

KEY WORDS: • taste • smell • flavor enhancement • elderly people • flavors • MSG

	INTRODUCTION

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
The number of elderly persons as well as their proportion of the world population is escalating rapidly. By the year 2025, there are expected to be 1.121 billion people over the age of 60 y, and most will have some sensory losses, including impairment of taste and smell perception. Both clinical and laboratory studies have found a progressive decline in taste and smell functioning, which tends to begin around 60 y of age and becomes more severe in persons >70 y of age (Schiffman, 1997 ). Taste and smell dysfunction in the elderly is caused by normal aging as well as certain disease states (such as cancer and Alzheimer’s disease), pharmacologic and surgical interventions, radiation and environmental exposure. These chemosensory deficits can alter food choices and intake and subsequently exacerbate medical conditions, impair nutritional status and immunity, alter food choices and produce weight loss (Duffy et al. 1995 , Griep et al. 1996 , Schiffman 1983 and 1997 ).

Chemosensory dysfunction is usually classified by the following nomenclature: ageusia (absence of taste), hypogeusia (diminished sensitivity of taste), dysgeusia (distortion of normal taste), anosmia (absence of smell), hyposmia (diminished sensitivity of smell) and dysomia (distortion of normal smell). Patients with hypogeusia generally require higher concentrations to detect and recognize a tastant, that is, they have elevated detection and recognition thresholds compared with normal controls. They may also perceive suprathreshold concentrations as less intense. Patients with dysgeusia often complain about taste distortions including bitter/metallic side tastes not usually associated with the foods that they are eating. Analogous impairments in smell perception occur for patients with hyposmia and dysosmia.

	Methods to compensate for chemosensory deficits

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Chemosensory deficits experienced by the elderly generally cannot be reversed. However, sensory interventions including intensification of the taste and odor of food can compensate for age-related perceptual losses. In our laboratory, commercial flavors and monosodium glutamate (MSG)²are added to food during and after preparation of a meal to enhance the smell and taste properties and improve palatability (Schiffman 1983 , 1997 and 1998 , Schiffman and Warwick 1993 ).

	Flavors

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Flavors are mixtures of odorous molecules that can be extracted directly from natural foods or can be synthesized in the laboratory after chromatographic and mass spectrographic analysis of natural products. In addition to the odorous molecules, flavors often contain nonvolatile compounds such as amino acids or salts that induce taste and/or somatosensory stimulation. Addition of flavors at optimal concentrations for the elderly (i.e., flavor enhancement) can improve food enjoyment and have a positive effect on food intake. For example, simulated chicken flavor can be added to chicken or chicken soup to provide a more intense "chicken" sensation.

Flavor enhancement differs from more traditional methods of increasing odor and taste sensations such as spices, herbs and salt. Spices and herbs add different flavors to the food rather than intensify the chemosensory properties of the actual foods. Because flavors are not spices, they do not irritate the mouth or stomach. Both the clinical and laboratory studies described below have found that flavor enhancement of foods for the elderly can improve immunity, functional status and quality of life.

	MSG

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
MSG is the sodium salt of the amino acid glutamic acid. It has a unique taste quality which is called "umami" in the Japanese language. There is no analogous word to describe this taste quality in the English language. "Umami" is used by the Japanese to describe the taste of MSG as well as the meaty taste of certain fish and broths. Rolls (1997) suggested that the umami quality signifies "protein taste." A variety of testing techniques have demonstrated that the taste quality of MSG does not fall within the qualitative taste range defined by the traditional four tastes of sweet, sour, salty and bitter (Schiffman 1997 ). MSG is often used commercially in mixtures with certain 5'-ribonucleotides including inosine-5'-monophosphate (IMP) and guanosine-5'-monophosphate (GMP). These compounds have potent synergistic effects with MSG, including a significant lowering of the MSG threshold level (Maga 1983 , Schiffman et al. 1994 ).

	Experimental studies of intensification of smell and taste

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
The five studies described below show the effects of sensory enhancement with flavors and/or MSG on food intake, satisfaction, immunity and salivation in the elderly. The results of these studies indicate that amplification of taste and smell can improve food palatability and acceptance, improve lymphocyte counts, increase salivary flow and increase secretion rate of salivary immunoglobulin A (sIgA).

	Study 1. Flavor enhancement increases T and B cell levels in elderly retirement home residents

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Schiffman and Warwick (1993) found that flavor enhancement of food for elderly retirement home residents resulted in improved immune status as determined by T and B cell levels. Eating flavor-enhanced foods also led to improvement in one anthropometric measure (grip strength). In this study, the elderly residents ate flavor-enhanced foods for 3 wk and the identical foods in unenhanced form for another 3 wk. Half of the subjects received enhanced food first and unenhanced food second; for the other half, the order was reversed. Six flavors were utilized throughout the study: roast beef, ham, natural bacon, prime beef, maple and cheese. These flavors were primarily odors; they were virtually tasteless and contained no NaCl or sweeteners.

The immune and functional improvements (i.e., increased T and B cell counts and improved grip strength) found in this study occurred as a result of intensifying the flavor of some but not all foods at a meal. Subjects ate more of the flavor-enhanced foods and less of the unenhanced foods. As a consequence, they consumed the same macro- and micronutrients on the enhanced and unenhanced arms of the study. That is, they consumed the same nutrients on both arms of the study; the only difference between the foods consumed during the enhanced and unenhanced arms was the flavor level experienced by the subjects. Yet, flavor enhancement improved immunity and grip strength. Similar results were found in an additional study that used MSG and flavors to intensify both taste and smell simultaneously (Schiffman 1998 ).

The improved immune status produced by flavor enhancement may result from one or more of the following four possibilities. First, direct neural-immune connections exist between the those parts of the brain that subserve olfaction and the immune system (Felten et al. 1991 ). Thus olfactory stimulation could boost immune function directly via these connections. Second, the elevated flavor levels may lead to greater release of digestive enzymes and produce better absorption of micronutrients. Third, there may be phytochemicals in the flavors that directly improve immunocompetence due to their biochemical actions. Fourth, flavor enhancement may improve mood, leading to reduced circulating cortisol. Cortisol is known to suppress the immune status.

	Study 2. Effect of taste and smell stimulation on secretion rate of salivary IgA in young and elderly persons

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Two experiments have found that taste and odor stimuli enhance secretion rate of salivary IgA in young and elderly individuals (Schiffman 1998 , Schiffman and Miletic 1999 ). In the first experiment, three stimuli were applied to the tongue as follows: 1) "flavor" drops (60% sugar, 5% cocoa powder and 0.1% Irish cream odor); 2) sugar (60%); and 3) water. The stimuli were applied three times in 1-g doses in a 1-h period (at t = 0, 30 and 60 min). In the second experiment, four different foods (corn, carrots, chicken broth and onion soup) were tested with and without MSG. Each food was consumed three times in 6.5-g samples in a 1-h period (at t = 0, 30 and 60 min). In both experiments, saliva was collected four times, i.e., before chemosensory stimulation (baseline) and directly after chemosensory stimulation at 0, 30 and 60 min.

The results of the first experiment showed that application of sugar (taste alone) and flavor (taste and odor combined) to the tongue induced significantly higher secretion rates of sIgA than the application of water in both young and elderly subjects. In addition, flavor application produced significantly higher absolute concentrations of sIgA than sugar application alone. Secretion rates of sIgA in young persons were significantly higher than those in elderly persons. In the second study, the increase in sIgA secretion rate for the elderly subjects at 30 and 60 min for each food with MSG was greater than that observed when the same food was consumed without MSG. The short-term increases in sIgA secretion rates in these two experiments may be due to the following: 1) the elevated salivary flow caused by reflex secretion of saliva containing sIgA, and 2) possible neural-immune interactions (Felten et al. 1991 ) that induced elevated absolute concentrations of sIgA (in the flavor condition in the first experiment).

	Study 3. Sensory enhancement of foods with MSG and flavors improves intake in sick elderly

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Schiffman (1998) reported that the addition of MSG (as well as flavors) to foods improved intake in 43 consecutive patients in a hospital setting. The patients had clinical manifestations of malnutrition, had a recent weight loss of 6% or more and/or were below average weight for height and age. During this study, the food on the patient’s plate was measured before and after eating on two consecutive days. The energy content of the food served to each patient was identical on the 2 d. The levels of MSG and flavors used in these studies were individualized on the basis of each patient’s taste and odor thresholds. Levels of MSG ranged from 0.3% to 1.0% depending on the degree of taste loss of each subject. MSG was always administered in mixtures with 5'-nucleotides. The Na⁺ levels did not exceed 2400 mg/d. The main finding was that the combination of MSG and flavor improved energy intake by 10% or more in 40 of 43 patients. In addition to increasing intake, clinical observations showed that sensory enhancement over a week or more resulted in an improvement in plasma protein levels (including somatomedin-C/insulin-like growth factor I, albumin and transferrin) and T-lymphocytes from abnormal to normal values for some patients.

	Study 4. Sensory enhancement of foods with MSG and flavors improves satisfaction in healthy elderly

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Foods that contained a combination of MSG and flavors were prepared and provided to relatively healthy elderly persons who consumed their meals at a cafeteria at a retirement center (Schiffman 1998 ). The subjects (mean age = 81.7 y) were divided into two groups. One group received unenhanced food for the first 4-wk period and food enhanced with MSG and flavors for the second 4-wk period. The order was reversed for the other group. The levels of MSG and flavors added to each food were optimized to the subjects’ preferences in pretesting at the retirement community. The foods to which the MSG and flavors were added included meats, soups, gravies, eggs and egg substitutes, vegetables, grits, stews, sauces and macaroni. Ratings of satisfaction for each meal were obtained in both the unenhanced and enhanced conditions.

The mean values for the ratings on each scale, tabulated across all foods in the two conditions, are shown in Table 1 . The results show that enhancement with MSG and flavors significantly improved acceptability of the these foods. Further analyses of ratings for the different food types revealed that the order of improvement was as follows: soups > meats > gravies > sauces > stews.

	Study 5. Sensory enhancement of foods with flavors increases preferences for cancer patients

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Most of our research to date has focused on the flavor enhancement of foods for healthy or frail elderly individuals. However, sensory intensification may be helpful in treating cancer, a disease that effects the elderly disproportionately (Cohen 1998 ). For example, a synthesis of the data suggests that 50% or more of cancer patients may have impaired taste and smell functioning during the course of their disease and treatment (DeWys and Walters 1975 ). Diminished taste sensitivity in cancer patients was associated with inadequate food intake and/or weight loss (DeWys and Walters, 1975 ).

We tested flavor preferences recently in 13 patients who were undergoing or had recently completed chemotherapy (10 subjects) or radiotherapy (3 subjects) for breast cancer. In a single-blind study, patients were given two samples of a food to taste and were asked which one they preferred. For all items, the majority of cancer patients preferred the flavor-enhanced food to the unenhanced food (Table 2 ). None of the patients reported an aversion to the foods that were tested.

	Explanation for results of sensory enhancement with flavors and MSG

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

 
Flavors probably exert their effect by increasing the number of molecules that interact with receptors on chemosensory membranes in the nose and oral cavity. This intensification of chemosensory stimulation induces more salivation, produces greater stimulation of the olfactory and limbic system of the brain and promotes immune function via mechanisms described above in Study 1.

MSG (with or without 5'-ribonucleotides) likely exerts its effect by adding another taste quality to the food, i.e., umami, which improves palatability (Bellisle et al. 1991 ). Neither MSG nor 5'-ribonucleotides appear to exert their effect by altering the perceived intensity of other components of foods. Neither MSG nor 5'-ribonucleotides altered the intensities of salts, sweeteners, amino acids, acids or bitter compounds as shown in Table 3 (Schiffman, unpublished data) using a testing method described by Schiffman et al. (1983) . Similar results were found using whole-mouth tests.

	SUMMARY

TOP ABSTRACT INTRODUCTION Methods to compensate for... Flavors MSG Experimental studies of... Study 1. Flavor enhancement... Study 2. Effect of... Study 3. Sensory enhancement... Study 4. Sensory enhancement... Study 5. Sensory enhancement... Explanation for results of... SUMMARY REFERENCES

	FOOTNOTES

 
¹ Presented at the International Symposium on Glutamate, October 12–14, 1998 at the Clinical Center for Rare Diseases Aldo e Cele Daccó, Mario Negri Institute for Pharmacological Research, Bergamo, Italy. The symposium was sponsored jointly by the Baylor College of Medicine, the Center for Nutrition at the University of Pittsburgh School of Medicine, the Monell Chemical Senses Center, the International Union of Food Science and Technology, and the Center for Human Nutrition; financial support was provided by the International Glutamate Technical Committee. The proceedings of the symposium are published as a supplement to The Journal of Nutrition. Editors for the symposium publication were John D. Fernstrom, the University of Pittsburgh School of Medicine, and Silvio Garattini, the Mario Negri Institute for Pharmacological Research.

² Abbreviations used: GMP, guanosine-5'-monophosphate; IMP, inosine-5'-monophosphate; MSG, monosodium glutamate; sIgA, salivary immunoglobulin A.

	REFERENCES

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1. Bellisle F., Monneuse M. O., Chabert M., Larue-Achagiotis C., Lanteaume M. T., Louis-Sylvestre J. Monosodium glutamate as a palatability enhancer in the European diet. Physiol. Behav. 1991;49:869-873[Medline]

2. Cohen H. J. Cancer and aging: overview. American Society of Clinical Oncology Ed 1998 ucation Book (Perry M. C., ed.), pp. 223–226. American Society of Clinical Oncology, Alexandria, VA.

3. DeWys W. D., Walters K. Abnormalities of taste sensation in cancer patients. Cancer 1975;36:1888-1896[Medline]

4. Duffy V. B., Backstrand J. R., Ferris A. M. Olfactory dysfunction and related nutritional risk in free-living, elderly women. J. Am. Diet. Assoc. 1995;95:879-884[Medline]

5. Felten D. L., Cohen N., Ader R., Felten S. Y., Carlson S. L., Roszman T. L. Central neural circuits involved in neural-immune interactions. Ader R. Felten D. L. Cohen N. eds. Psychoneuroimmunology 1991:3-26 Academic Press San Diego, CA.

6. Griep M. I., Verleye G., Franck A. H, Collys K., Mets T. F., Massart D. L. Variation in nutrient intake with dental status, age and odour perception. Eur. J. Clin. Nutr. 1996;50:816-825[Medline]

7. Maga J. A. Flavor potentiators. Crit. Rev. Food Sci. Nutr. 1983;18:231-312[Medline]

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9. Schiffman S. S. Taste and smell in disease. N. Engl. J. Med. 1983;308:1275–1279 and 1337–1343[Medline]

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12. Schiffman S. S., Lockhead E., Maes F. W. Amiloride reduces the taste intensity of Na⁺ and Li⁺ salts and sweeteners. Proc. Natl. Acad. Sci. U.S.A. 1983;80:6136-6140[Abstract/Free Full Text]

13. Schiffman S. S., Miletic I. Effect of taste and smell on secretion rate of salivary IgA in elderly and young persons. Journal of Nutrition, Health and Aging 1999;3:158-164

14. Schiffman S. S., Sattely-Miller E. A., Zimmerman I. A., Graham B. G., Erickson R. P. Taste perception of monosodium glutamate (MSG) in foods in young and elderly subjects. Physiol. Behav. 1994;56:265-275[Medline]

15. Schiffman S. S., Warwick Z. S. Effect of flavor enhancement of foods for the elderly on nutritional status: food intake, biochemical indices and anthropometric measures. Physiol. Behav. 1993;53:395-402[Medline]

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