Elsevier

Appetite

Volume 55, Issue 1, August 2010, Pages 1-10
Appetite

Research review
Glutamate. Its applications in food and contribution to health

https://doi.org/10.1016/j.appet.2010.05.002Get rights and content

Abstract

This article reviews application of glutamate in food and its benefits and role as one of the common food ingredients used. Monosodium glutamate is one of the most abundant naturally occurring amino acids which frequently added as a flavor enhancer. It produced a unique taste that cannot be provided by other basic taste (saltiness, sourness, sweetness and bitterness), referred to as a fifth taste (umami). Glutamate serves some functions in the body as well, serving as an energy source for certain tissues and as a substrate for glutathione synthesis. Glutamate has the potential to enhance food intake in older individuals and dietary free glutamate evoked a visceral sensation from the stomach, intestine and portal vein. Small quantities of glutamate used in combination with a reduced amount of table salt during food preparation allow for far less salt to be used during and after cooking. Because glutamate is one of the most intensely studied food ingredients in the food supply and has been found safe, the Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and World Health Organization placed it in the safest category for food additives. Despite a widespread belief that glutamate can elicit asthma, migraine headache and Chinese Restaurant Syndrome (CRS), there are no consistent clinical data to support this claim. In addition, findings from the literature indicate that there is no consistent evidence to suggest that individuals may be uniquely sensitive to glutamate.

Introduction

For many years, food additives have been used for flavoring, coloring and extension of the useful shelf-life of food, as well as the promotion of food safety (Rangan & Barceloux, 2009). Flavoring systems are very important in savory food manufacturing. Flavorings can play an important nutritional role, particularly in foods that are not very flavorful, by providing the needed appeal (Löliger, 2000). Foods and ingredients high in free amino acids or made up of protein hydrolysates have been used in cooking for many centuries, in many cultures, in order to enhance the sensory qualities of various foods (Bellisle, 1999). Umami taste helps improve flavor in foods, by giving meaty and savory flavors. The most closely studied flavor enhancer is monosodium glutamate, the sodium salt of glutamic acid. Glutamate is a frequently used flavor enhancer in foods, enhances the savory flavors imparted by glutamic acid, which occurs naturally in proteinaceous foods e.g. meats, seafood, stews, soups, sauces (Rangan & Barceloux, 2009). There is no precise definition for basic tastes; however they are defined by prototypical stimuli. The four traditional basic tastes are sweet, sour, salty, and bitter, and the fifth widely accepted basic taste is umami.

The natural occurring glutamate is in the form of l-glutamic acid, firstly discovered in 1866 by Karl Ritthausen, a German scientist, who isolated it from the acid hydrolysate of wheat gluten (Ritthausen, 1913). Salts of glutamic acid were first discovered in 1908 when Professor Kikunae Ikeda, a Japanese scientist identified the unique taste of umami attributed by glutamic acid; he identified umami as fifth basic taste after sweet, sour, salty and bitter in the tongue, where umami receptor taste located. Professor Ikeda, also has extracted and identified glutamic acid from soup stock prepared from konbu seaweed as the source of the umami taste, which from then, umami is described as savory, or meat or broth-like taste means delicious in Japanese (Ikeda, 1909, Ninomiya, 2001). In 1913, Kodama, isolated 5′-inosinic acid from dried skipjack as another key component of the konbu seaweed stock. In 1957, Kinoshita explored a bacterial strain Micrococcus glutamicus (later changed to Corynebacterium glutamicus) which could produce and accumulate large amounts of l-glutamic acid (Kinoshita, Udaka, & Shimeno, 1957). In 1960, Kuninaka isolated 5′-guanylate and recognized its role as key component of umami taste in the broth of dried shiitake mushroom (Kuninaka, 1960).

There have been numerous studies on umami taste and glutamate and their relation to food palatability and flavor acceptance (Baryłko-Pikielna and Kostyra, 2007, Bellisle, 1999, Bellisle, 2008, Fuke and Shimizu, 1993, Gould et al., 2008, Yeomans et al., 2008), nutritional considerations (Bellisle, 1999), presence in foodstuffs (Daniels et al., 1995, Khairunnisak et al., 2009, Mau, 2005, Nicholas and Jones, 1991, Populin et al., 2007, Skurray and Pucar, 1988), sensing in the oral cavity and gut (Burrin et al., 2008, Kurihara and Kashiwayanagi, 2000), physiological role in the food digestion (Uneyama, Gabriel, Kawai, Tomoe, & Torii, 2008), safety (Mallick, 2007, Simon, 2000, Walker and Lupien, 2000), and adverse effects (Diniz et al., 2005, Freeman, 2006, Ortiz et al., 2006). This review focuses on applications of glutamate as a food additive in food and its contribution to health.

Section snippets

Glutamate natural occurrence

Glutamate, one of the most common amino acids found in nature, is present in many proteins and peptides and most tissues. Glutamate is also produced in the body and binds with other amino acids to form a structural protein (Filer & Stegink, 1994). When glutamate bounds to protein molecule, it is tasteless and does not provide umami taste to food. However, protein hydrolysis during fermentation, aging, ripening and heat cooking process will liberate free glutamate (Yoshida, 1998). Glutamate is a

Glutamate as a food additive

Although glutamate is naturally occurring in many foods, it is frequently added as a flavor enhancer. Foods containing large amounts of free glutamate, such as tomatoes, mushrooms and cheese are traditionally used to obtain savory dishes (Giacometti, 1979, Yamaguchi and Ninomiya, 2000). When glutamate is added to foods, it provides a flavoring function similar to naturally occurring free glutamate (Yamaguchi & Ninomiya, 2000). Therefore, it is used to enhance the natural flavors of meats,

Metabolism in human body

Glutamate and disodium 5′-monoisinate (IMP) are the two amino acids that have received attention as oral stimulators of appetite and metabolism. Study by Lenjeune and Smeets (2007) showed that the addition of glutamate and IMP to a high-protein diet has a significant effect on desire to eat and no effect on energy metabolism. Adding glutamate to foods increases their umami taste quality, their acceptability and their consumption (Prescott, 2004). Study on novel savory flavors with glutamate has

Nutritional aspects

l-glutamate is a multifunctional amino acid involved in taste perception, intermediary metabolism, and excitatory neurotransmission (Kondoh, Mallick, & Torii, 2009). The oral stimulation by glutamate solution (umami taste) increases secretion of saliva and promotes mastication, and activation of the efferent pathways of the gastric and pancreatic vagal rami to facilitate gastric and pancreatic functions and to increase gastric endocrine and pancreatic exocrine and endocrine secretions

Safety evaluation and regulations

In 1958 the U.S. Food and Drug Administration (FDA) designated glutamate as a Generally Recognized As Safe (GRAS) ingredient, along with many other common food ingredients such as salt, vinegar and baking powder (USDHHS, 1958). There was general consensus in the scientific community, based on numerous biochemical, toxicological and medical studies conducted over four decades, that glutamate is safe for the general population, including pregnant and lactating women, and children (IFIC, 2003).

Safety concern

Worldwide glutamate consumption has increased dramatically in recent decades (He et al., 2008, Hermanussen et al., 2006). There was a safety concern of glutamate with respect to epidemic overweight or obesity. While there are not much published studies on glutamate intake in relation to obesity or overweight in human, a single study by He et al. (2008) from China provided human data that glutamate intake may be associated with increased risk of overweight independent of physical activity and

Conclusions

The main goal of this article was to review the benefits and role of glutamate as one of the common food ingredients used all over the world. Glutamate is one of the most common amino acids and present in many proteins and peptides and most tissues. It is a crucial component of the taste of umami or savory which contained abundantly in various foods, including vegetables, seafood, meat and cheese, and contributes greatly to the characteristic tastes of these foods. Although glutamate is

References (128)

  • S. Fuke et al.

    Sensory and preference aspects of umami

    Trends in Food Science and Technology

    (1993)
  • R.S. Geha et al.

    Review of alleged reaction to monosodium glutamate and outcome of a multicenter double-blind placebo-controlled study

    Journal of Nutrition

    (2000)
  • P. Germano et al.

    An evaluation of clinical reactions to monosodium glutamate (GLUTAMATE) in asthmatics, using a blinded placebo-controlled challenge

    Journal of Allergy and Clinical Immunology

    (1991)
  • L. Johansson et al.

    Preference for tomatoes, affected by sensory attributes and information about growth conditions

    Food Quality and Preference

    (1999)
  • T. Kondoh et al.

    Activation of the gut-brain axis by dietary glutamate and physiologic significance in energy homeostasis

    American Journal of Clinical Nutrition

    (2009)
  • T. Kondoh et al.

    MSG intake suppresses weight gain, fat deposition and plasma leptin levels in male Sprague–Dawley rats

    Physiology and Behavior

    (2008)
  • K. Kurihara

    Glutamate. From discovery as a food flavor to role as a basic taste (umami)

    American Journal of Clinical Nutrition

    (2009)
  • K. Kurihara et al.

    Basic characteristics of glutamate and umami sensing in the oral cavity and gut

    Journal of Nutrition

    (2000)
  • J. Löliger

    Function and importance of glutamate for savory foods

    Journal of Nutrition

    (2000)
  • A. Niijima

    Effects of oral and intestinal stimulation with umami substance on gastric vagus activity

    Physiology and Behavior

    (1991)
  • R.L. O’Kane et al.

    Na(+)-dependent glutamate transporters (EAAT1, EAAT2, and EAAT3) of the blood–brain barrier. A mechanism for glutamate removal

    Journal of Biological Chemistry

    (1999)
  • G.G. Ortiz et al.

    Monosodium glutamate-induced damage in liver and kidney. A morphological and biochemical approach

    Biomedicine and Pharmacotherapy

    (2006)
  • T. Populin et al.

    A survey on the presence of free glutamic acid in foodstuffs, with and without added monosodium glutamate

    Food Chemistry

    (2007)
  • J. Prescott

    Effects of added glutamate on liking for novel food flavors

    Appetite

    (2004)
  • J. Prescott et al.

    Does information about MSG (monosodium glutamate) content influence consumer ratings of soups with and without added MSG?

    Appetite

    (2002)
  • M. Ramos et al.

    Effect of freezing on soluble nitrogen fraction of Cabrales Cheese

    Food Chemistry

    (1987)
  • C. Rangan et al.

    Food additives and sensitivities

    Disease-a-Month

    (2009)
  • P.J. Reeds et al.

    Intestinal glutamate metabolism

    Journal of Nutrition

    (2000)
  • K. Roininen et al.

    Effect of umami taste on pleasantness of low-salt soups during repeated testing

    Physiology and Behavior

    (1996)
  • R.A. Simon

    Glutamate safety in the food supply-additive-induced urticaria. Experience with monosodium glutamate (MSG)

    Journal of Nutrition

    (2000)
  • G.R. Skurray et al.

    l-Glutamic acid content of fresh and processed foods

    Food Chemistry

    (1988)
  • J.M. Spergel et al.

    Food allergy and additives. Triggers in asthma

    Immunology and Allergy Clinics of North America

    (2005)
  • L.D. Stegink et al.

    Modulating effect of Sustagen on plasma glutamate concentration in humans ingesting monosodium l-glutamate

    American Journal of Clinical Nutrition

    (1983)
  • L.D. Stegink et al.

    Effect of carbohydrate on plasma and erythrocyte glutamate levels in humans ingesting large doses of monosodium l-glutamate in water

    American Journal of Clinical Nutrition

    (1983)
  • L.D. Stegink et al.

    Plasma glutamate concentrations in adult subjects ingesting monosodium l-glutamate in consommé

    American Journal of Clinical Nutrition

    (1985)
  • Y. Akiba et al.

    Luminal l-glutamate enhances duodenal mucosal defense mechanisms via multiple glutamate receptors in rats

    American Journal of Physiology: Gastrointestinal and Liver Physiology

    (2009)
  • D.R. Altman et al.

    Double-blind placebo-controlled challenge (DBPCC) of persons reporting adverse reactions to monosodium glutamate (GLUTAMATE)

    Journal of Allergy and Clinical Immunology

    (1994)
  • T. Altug et al.

    Influence of monosodium glutamate on flavor acceptability and on the reduction of sodium chloride in some readymade soups

    Chemie Mikrobiologie Technologie der Lebensmittel

    (1993)
  • K. Anantharaman

    In utero and dietary administration of monosodium l-glutamate to mice: reproductive performance and development in a multigeneration study

  • G.J. Augustine et al.

    Exocytosis. Proteins and perturbations

    Annual Review of Pharmacology and Toxicology

    (1996)
  • F. Bellisle

    Experimental studies of food choices and palatability responses in European subjects exposed to the umami taste

    Asia Pacific Journal of Clinical Nutrition

    (2008)
  • F. Bellisle et al.

    Monosodium glutamate as a palatability enhancer in the European diet

    Physiology and Behavior

    (1991)
  • K. Beyreuther et al.

    Consensus meeting. Monosodium glutamate. an update

    European Journal of Clinical Nutrition

    (2007)
  • H.K. Biesalski et al.

    Na-Glutamat

    Akt Ernahr Med

    (1997)
  • D.G. Burrin et al.

    Emerging aspects of dietary glutamate metabolism in the developing gut

    Asia Pacific Journal of Clinical Nutrition

    (2008)
  • S.P. Chi et al.

    Predicting optimum monosodium glutamate and sodium chloride concentrations in chicken broth as affected by spice addition

    Journal of Food Processing and Preservation

    (1992)
  • Codex. (1989). Codex class names and the international numbering system for food additives. CAC/GL 36-1989,...
  • J.J. Cordoba et al.

    Evolution of free amino acids and amines during ripening of Iberian cured ham

    Journal of Agricultural and Food Chemistry

    (1994)
  • M.A. Cousin et al.

    Mechanisms of synaptic vesicle recycling illuminated by fluorescent dyes

    Journal of Neurochemistry

    (1999)
  • D. Daniels et al.

    Determination of free glutamic acid in a variety of foods by high-performance liquid chromatography

    Food Additives and Contaminants

    (1995)
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