Science, Art, Litt, Science based Art & Science Communication
Recently an interesting thing happened. I drank some water in my sister's home. The water was collected from a water purifier. The water tasted bitter. I told this to my sister. She too drank it and said, it tasted normal to her. Then I asked others too to drink the water and they all said, it tasted normal.
Then why did I alone find the water bitter?
I always find mineral water in plastic water bottles bitter. The chemicals leached into water might be a reason for this.
Not only that some foods too taste more bitter to me. I always complain about brinjals, cabbages, cucumbers, drumsticks and some leafy vegetables and refused to eat them when I was very young and my mother used to scold me.
In summer some fruits and vegetables taste bitter to many. There are various reasons for this. I wrote on this earlier and you can read about them if you are interested here: why-do-some-fruits-and-vegetables-taste-bitter-in-summer.
That is a different issue.
Some people can eat all foods without any complaints while some cannot.
Many studies have shown that the flavour of food is by far the most important factor in determining what foods we choose to eat.
However, Ayurveda, the ancient medical system of India, recognizes six tastes: sweet, sour, salty, bitter, pungent, and astringent. Some examples of these 'Indian tastes':
Sweet:
- Most grains such as wheat, rice, barley, and corn
- Pulses (legumes), such as beans, lentils, and peas
- Milk and sweet milk products such as ghee, cream, and butter
- Sweet fruits (especially dried) such as dates, figs, grapes, pear, coconut, and mango
- Cooked vegetables such as potato, sweet potato, carrot, beetroot, cauliflower, and string beans
- Sugar in any form such as raw, refines, brown, white, molasses, and sugar cane juice
Sour:
- Sour fruits such as lemon, lime, sour orange, sour pineapple, passion fruit, sour cherries, plum, and tamarind
- Sour milk products such as yogurt, cheese, whey, and sour cream
- Fermented substances (other than cultured milk products) such as wine, vinegar, soy sauce, or sour cabbage
- Carbonated beverages (including soft drinks or beer)
Salty:
- Any kind of salt such as rock salt, sea salt, and salt from the ground
- Any food to which salt has been added
Pungent:
- Spices such as chili, black pepper, mustard seeds, ginger, cumin, cloves, cardamom, and garlic
- Mild spices such as turmeric, anise, cinnamon, and fresh herbs such as oregano, thyme, and mint
- Raw vegetables such as radish, onion, and cauliflower
Bitter:
- Vegetables such as chicory and bitter gourd; other green leafy vegetables such as spinach, green cabbage, and brussels sprouts
- Fruits such as olives, grapefruit, and cocoa
- Spices such as fenugreek and turmeric
Astringent:
- Turmeric, honey, walnuts, and hazelnuts
- Pulses such as beans, lentils, peas
- Vegetables such as sprouts, lettuce, and other green leafy vegetables; most raw vegetables
- Fruits such as pomegranate, berries, persimmon, rose, apple, and most unripe fruits
The ability to sense each of these tastes is believed to have evolved to improve the chances of survival for our earliest ancestors. The sweet taste of fruit indicates a source of sugars for energy. Umami is believed to have evolved as a means to detect protein and essential amino acids. Salt is required for regulating the level of bodily fluids. Sour indicates the presence of spoiled food as we might find in old milk. Many toxic compounds found in plants produce a very bitter taste. And fat is another important source of energy as well as essential fatty acids. Our sense of taste evolved to detect non-volatile molecules that we cannot smell.
In contrast to the small number of basic tastes, humans are able to recognize more than 10,000 different odours. Unlike taste, humans are amazingly sensitive to smell.
We sense the smell of food by two routes. Sniffing through our nose is called orthonasal smell, while the aroma released up through the back of our mouth into our nose when we chew and swallow food is called retronasal smell. Orthonasal and retronasal smells appear to be processed in different parts of the brain. The latter is the most important route for sensing the aroma of food and is believed to account for as much as 80-85% of the flavour of food. That explains why we can’t detect the flavour of food when we have a cold and our nose is blocked.
The taste and aroma of food are sensed through special receptors (proteins) on the surface of taste and olfactory cells in our mouth and nose. They provide a direct link between our brain and the outside world.
Some of the receptors for taste are linked together, such as sweet and umami, which probably explains why we like foods that are both sweet and savoury. There are other interesting interactions. For example, salt helps mask bitterness (although bitterness does not mask salt), and saltiness and pungency are reduced by fat. When it comes to health one very important recent discovery is that taste receptors, especially for sweet taste, are located throughout our gastrointestinal tract . Receptors for bitter and umami are also present.
This brings us to genetic differences in our ability to taste food. It has been known for many years that some people are extremely sensitive to the taste of bitter substances, while others perceive little or no bitter taste.
The terms super-taster and non-taster are attributed to Linda Bartoshuk, now a professor at the University of Florida, and a pioneer in studying the genetic differences of taste.
Whereas super-tasters cringe at the taste of even the smallest amount of PROP, average tasters perceive only a faint bitter taste. The reason for this difference turns out to be fairly simple and obvious. Super-tasters have many more visible taste papillae than tasters and non-tasters. This is illustrated in the figure below. This means they have many more taste cells with receptors for bitter taste. Super-tasters are also more sensitive to sweet, salty and umami tastes, but to a lesser extent .
It would seem that super-tasters might have an advantage over everyone else in their ability to taste and enjoy food. Unfortunately, this is not the case. Because they are so sensitive to bitter they tend to be very picky eaters and dislike many foods.
Average tasters tend to like most foods. They are not repelled by food that tastes overly bitter and unpleasant, yet their sense of taste is keen enough that they can enjoy most food without drowning it with salt or pungent sauce. Based on the following reported observations genetic variation in taste may affect food preference, diet and health.
Although consensus has not been reached on the significance of these observations, numerous correlations of health outcomes with sensitivity to PROP and bitter taste demonstrate a strong relationship exists between our sense of taste and smell and overall health status. More research is clearly warranted. PROP test strips are safe and easy to use and available online if you would like to determine your taste status. Or simply try examining your tongue in the mirror.
But if you’re a super taster, you need not give up eating some foods because if you have repeated exposures to these tastes, you even overcome that dislike towards them.
Now you know why I am a picky eater. Because I am a super-taster! Don't tease me!
Sources: Harvard university education centre, Sharecare, with some inputs from SCI-ART LAB
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https://medicalxpress.com/news/2020-04-coffee.html?utm_source=nwlet...
When people were tested after drinking coffee, they became more sensitive to sweetness, and less sensitive to bitterness
"It's probably some of the bitter substances in the coffee that create this effect
Alexander W. Fjaeldstad et al, Chemosensory Sensitivity after Coffee Consumption Is Not Static: Short-Term Effects on Gustatory and Olfactory Sensitivity, Foods (2020). DOI: 10.3390/foods9040493
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https://phys.org/news/2020-04-biologists-sweet-sugary-foods-diminis...
One process responsible for this occurrence: cool temperatures suppress the appeal of sweetness. However, these conditions did not affect the sugar neurons themselves. Rather, they acted via other sensory cells by way of a protein originally discovered to sense light in the eye. Despite this, the perception of coolness in sugary food is not altered by light. The results appear in the journal Current Biology.
Qiaoran Li et al. Temperature and Sweet Taste Integration in Drosophila, Current Biology (2020). DOI: 10.1016/j.cub.2020.03.066
our own genetics mean we don’t all taste chemical compounds the same. We have many thousands of different odour receptors in our brains, and many different combinations of taste receptors on our tongues. These genetic differences are one of the reasons why coriander tastes different to different people. Those with a variant of the OR6A2 gene perceive the leaves as having a soapy flavour, which is thanks to the aldehyde compounds in coriander that activate this receptor variant.
Depending on whether you have a functioning or non-functioning copy of certain taste receptor genes, you may not be able to taste certain compounds at all. In the other extreme, if you have two working copies of a particular gene, some foods may taste unbearably bitter and unpleasant.
Another classic example is Brussels sprouts. Some people love them, while others loathe them. This is because of the gene TAS2R38 which gives us the ability to taste the bitter glucosinolate compounds in these vegetables – as well as rocket.
Those people with two working copies of the gene are bitter “supertasters”. People with only one are “medium tasters”, while those with no working copies are “blind” to these compounds. So what is intense and inedible to one person might be pleasant and mild to another.
This partly explains people’s general food preferences – and rocket leaves are an excellent example of these processes in action. A consumer study of rocket leaves showed that some people like them hot and pungent, others like them sweet and mild, and others just don’t like them at all.
However, people’s culture and life experience probably also determine whether they like rocket and other foods. A previous study of rocket showed that people’s genetic differences are not necessarily an indicator of whether they will like something. It’s perfectly possible to be a bitter “supertaster” and like rocket and Brussels sprouts depending on your upbringing and exposure to them.
Another study showed that preference for flavour and pungency of white radish is linked to differences in geography and culture. Japanese and Korean people liked pungency created by an isothiocyanate much more than Australians. Pickled radish is a common condiment in Asian countries: being regularly exposed to a food may predispose people to like it, irrespective of their taste sensitivity.
Very little is currently known about the interactions between plant and human genotypes. But ongoing research aims to find out which compounds people with different TAS2R38 genotypes are sensitive to. This will make it possible in the future to selectively breed in (or out) certain genes, and produce rocket types tailored to a person’s preferences.
https://theconversation.com/rocket-arugula-rucola-how-genetics-dete...
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https://theconversation.com/four-reasons-why-some-people-become-sup...
Although coffee is very popular in the world, it is also known for its bitter taste.
Compounds contained in the coffee such as caffeine contribute to the bitterness to varying degrees. A recent study conducted by the Leibniz-Institute for Food Systems Biology and the Technical University of Munich (TUM) provides new insights into the molecular interactions between bitter substances and bitter receptors. This is of relevance not only for taste perception.
Caffeine is surely the best-known bitter coffee constituent. However, this stimulating substance is not solely responsible for the bitter taste of the beverage. The latest findings from a study conducted by the Freising team of scientists confirm this. Using a cell-based testing system - a type of artificial tongue - and docking analyses, the team investigated five different bitter coffee constituents. The tests included the bitter substance mozambioside identified in Arabica beans, its roast product bengalensol, and the well-known coffee compounds cafestol, kahweol, and caffeine.
Based on the results of their study, the research team assumes that mainly two of the 25 human bitter taste receptors respond to the coffee's constituents. Whereas a relatively high concentration of caffeine is necessary to stimulate the receptors TAS2R46 and TAS2R43, considerably smaller amounts of the other four substances are needed. The caffeine concentration required to activate the bitter taste receptor TAS2R43 to the same degree as mozambioside or bengalensol was about 30 and 300 times higher, respectively, says lead author Tatjana Lang from the Leibniz-Institute for Food Systems Biology.
Further studies conducted by the researchers suggest that the bitter substances contained in coffee interact with each other. These studies showed that kahweol and mozambioside exhibit similar binding properties for the bitter taste receptor TAS2R43. Compared to mozambioside, however, kahweol receptor activation was relatively weak and, depending on the dose, was capable of inhibiting the mozambioside-induced activation of the bitter taste receptor. Researchers, therefore assume that kahweol can reduce the bitter taste elicited by TAS2R43 by suppressing more effective bitter substances at the receptor
The study results are exciting from another perspective as well : these findings indicate that bitter coffee substances quite specifically activate two of the 25 bitter taste receptors. We furthermore know that both types of receptors are present not only in taste cells. TAS2R43 is also present in the stomach and in conjunction with caffeine plays a role in the regulation of gastric acid secretion. The question now arises as to how coffee constituents like bengalensol, which activate the receptor with much higher potency, might be involved in this regulatory process."
It is also interesting that many people do not possess the bitter taste receptor TAS2R43 due to a genetic variation. This could explain the differences in individual coffee taste perception or its tolerability.
Sources:
Lang T, Lang R, Di Pizio A, Mittermeier VK, Schlagbauer V, Hofmann T, Behrens M (2020) J Agric Food Chem, DOI: 10.1021/acs.jafc.0c01373. Numerous compounds orchestrate coffee's bitterness
https://pubs.acs.org/doi/10.1021/acs.jafc.0c01373
Liszt KI, Ley JP, Lieder B, Behrens M, Stöger V, Reiner A, Hochkogler CM, Köck E, Marchiori A, Hans J, Widder S, Krammer G, Sanger GJ, Somoza MM, Meyerhof W, Somoza V (2017) Proc Natl Acad Sci, 114(30):E6260-E6269, DOI: 10.1073/pnas.1703728114. Caffeine induces gastric acid secretion via bitter taste signaling in gastric parietal cells.
Open Access: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5544304/
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