Senses And Ingredients
What Is Umami? Glutamate In The Language Of Food
A tomato’s outer flesh and the soft pulp around its seeds carry different taste compositions within the same fruit. Glutamate, associated with umami, lets us investigate one such difference. From kombu stock to a tomato-based hot sauce, this taste quality helps explain why an ingredient cannot be described through sweetness and sourness alone.
What Does Umami Taste Like?
Umami is one of the basic taste qualities, alongside sweet, sour, salty and bitter. Bitterness is distinct from the heat of chilli. Descriptions such as ‘meaty’ or ‘broth-like’ help us recognise umami without requiring meat in the food: plant ingredients can also contain compounds associated with this taste.
Calling a dish delicious expresses a judgment about the whole experience. Umami names a more specific sensory quality, perceived together with aroma, temperature, texture and other tastes. Using it as a synonym for liking would make the particular taste detail less clear.
A tomato offers a familiar way to understand the distinction. Its umami quality, aroma, texture and other tastes together form its sensory portrait. In a hot sauce containing tomato, we can describe umami, chilli heat and the sauce’s aroma separately. Understanding how prominent umami is requires looking beyond the ingredient’s name to how the tomato is incorporated and how the finished sauce tastes.
Differences can also occur within an ingredient. In 2007, Oruna-Concha and colleagues compared the outer flesh and the inner pulp surrounding the seeds of thirteen tomato varieties. Free-amino-acid analysis found mean glutamic acid concentrations of 1.26 g/kg in the flesh and 4.56 g/kg in the pulp; the size of the difference varied by variety. Knowing which tissue was examined under the name “tomato” makes the distribution of umami-related compounds more visible.
From Kombu To A Scientific Concept
In 1908, Japanese chemist Kikunae Ikeda investigated the distinctive taste of kombu broth and connected it with glutamate. A preparation already familiar in the kitchen became a scientific question about a particular compound. The research sought to distinguish a taste quality within a known food.
The 1908 research was followed by Ikeda’s paper on new seasonings in 1909. Its English rendering, published in Chemical Senses in 2002, records his proposal of ‘umami’ for a quality he distinguished from four familiar tastes. A word arising from a culinary observation thereby reached readers in another language.
Kombu was the concrete material of this investigation. Umami became a taste concept that could be examined across different foods. A question about one preparation opened a way to investigate a similar sensory quality in other ingredients.
Glutamic Acid, Glutamate And MSG
Glutamic acid is an amino acid. ‘Glutamate’ names its ionised form; ‘monosodium glutamate’, or MSG, is its sodium salt. Umami describes a sensory quality, while MSG identifies a particular chemical substance. Using each name precisely keeps the taste experience distinct from a compound’s identity.
The form in which glutamate occurs also matters. Glutamate incorporated into proteins and free glutamate have different sensory implications. Kurihara’s 2015 review explains the relationship between free glutamate and umami, and how protein breakdown can release it. Protein content alone therefore cannot establish a food’s umami intensity.
What the FDA’s tomato and cheese examples share is a taste quality associated with glutamate. The freshness of tomato and a cheese’s distinctive aroma and texture provide it with different surroundings. Recognising the same taste concept in two ingredients does not make their complete flavours alike.
How Nucleotides Change The Response
IMP and GMP appear alongside glutamate in umami research. The abbreviations refer to nucleotides associated with 5′-inosinate and 5′-guanylate. Together with glutamate, they can enhance the umami response. Synergy describes a combined response that can exceed what would be expected from the compounds’ separate effects.
The combined response to glutamate and nucleotides has also been investigated at the level of the receptor pair formed by the proteins T1R1 and T1R3. Li and colleagues followed responses through increases in intracellular calcium in cells expressing human receptors. Comparing different glutamate concentrations with and without IMP, they reported that nucleotides could enhance the response to glutamate. The source of the receptor is also part of the comparison: in 2013, Toda and colleagues compared human and mouse receptors in cell experiments, examining their different selectivity for amino acids.
These experiments investigate receptor responses under specified conditions. Their culinary relevance lies in explaining how one compound’s effect can change in the presence of others. This interaction helps explain a dish’s taste layer; together with aroma, texture, other sensations and personal preference, that layer becomes part of the whole flavour experience.
Different Sensory Layers In One Ingredient
| Concept | What It Describes | Example Description |
|---|---|---|
| Umami | A basic taste quality | Broth-like taste |
| Aroma | Qualities perceived through smell | Herbal or fruity smell |
| Texture | Physical structure and feel in the mouth | Smooth or particulate |
| Pungency | A chemesthetic sensation | The burning sensation of chilli |
Returning to a tomato-based hot sauce, we can attend separately to umami, fruity aroma and pepper burn. They describe a taste quality, smell and a chemesthetic sensation. The details we recognise by separate names are still experienced together in the mouthful; umami becomes one part we can distinguish more precisely within the whole.
Sources And Further Reading
- NIDCD · How does the sense of taste work?
Reading area: Institutional explanation: basic tastes, smell and chemesthetic sensations within flavour.
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- FDA · The identity and history of monosodium glutamate
Reading area: MSG's chemical identity, Ikeda's 1908 research and examples of glutamate in foods.
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- Kikunae Ikeda · On a new seasoning, 1909
Reading area: Publication record and scan of Ikeda's original Japanese paper, 1909.
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- Kikunae Ikeda · New Seasonings, English rendering, 2002
Reading area: The open extract of the 2002 English rendering: the proposed name umami.
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- Kenzo Kurihara · Umami: taste, compounds and research history, 2015
Reading area: A 2015 review of free glutamate, IMP/GMP, umami history and receptor research.
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- Toda and colleagues · Ligand specificity in the umami receptor, 2013
Reading area: A 2013 cell study of differing amino-acid selectivity in human and mouse T1R1/T1R3 receptors.
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- Li and colleagues · Human receptors for sweet and umami taste, 2002
Reading area: Original research abstract and Figure 3B–C captions; human T1R1/T1R3 expressed in cells, intracellular calcium responses and glutamate concentration comparisons with and without IMP.
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- NIDCD · The two routes of smell
Reading area: Institutional explanation of smell through the nostrils and the throat-to-nose route.
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- Oruna-Concha and colleagues · Glutamic acid and 5′-ribonucleotides in tomato flesh and pulp, 2007
Reading area: Original research abstract; tissue comparison and mean glutamic acid concentrations in thirteen tomato varieties. Journal of Agricultural and Food Chemistry 55, 5776–5780; DOI 10.1021/jf070791p.
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