Eating with the Brain

Updated: Feb 18

Everything is created in the brain. If it were not the interpretations that our neurons make about the stimuli that come to them, gastronomy would not even exist. The brain is to blame that we enjoy surprises, that we prefer a dish or another or that we hate Brussels sprouts and instead, we find delicious truffles.



The food choices are conditioned by factors, such as the history and tradition, family and friends' influence, the economy (from the cost of food to the purchasing power) and the elements related to psychology, such as preferences.

The preference for the sweet taste and the rejection of bitter substances or spicy spices (which produce irritation in the mouth and throat) seem to be innate but most food preferences are acquired through experience.

David Jackson, Director of Consumer Innovation, Skin Health at GSK said that the hunter-gatherers depended on the sense of smell. For instance, the smell of sulfur indicated the presence of bacteria in food. Eating them could make them sick. (1)


Similarly, evolution may explain innate aversions to bitter tastes. Some inedible plants are bitter and those who detected this association were more likely to survive.

Avoiding eating new foods is called food neophobia and is defined as an overwhelming fear of new or unfamiliar foods. It is, in fact, a mechanism of adaptation typical of many species whose objective is to avoid the intake of food or substances that could be dangerous.


The taste of food is not the same for everyone because all the senses intervene in the process. Professor Barry C. Smith, philosopher and director of the Institute of Philosophy at the School of Advanced Study at University of London, explains that this phenomenon is due to the fact that we use all our senses when we taste food. Depending on each person, the taste varies. (recommended here).


How we taste things depends largely on the number and type of taste receptors we are born with, says flavour scientist and chef, Associate Professor Russell Keast from the Area School of Exercise and Nutrition Sciences at Deakin University. These taste receptors are clustered within the taste buds on the tongue and in the upper part of the mouth, and they react specifically to salty, sweet, sour or bitter foods.


"Somebody who's got a lot more receptors for specific chemicals in food will perceive them as being more intense", Keast says.

"It's almost like a de facto marker of the number of taste receptors you have, so people who can taste broccoli as bitter, we often call 'supertasters'."In general 20 per cent of the population will be supertasters, 30 per cent will be non-tasters and the rest will fall somewhere in the middle," says Keast. (2)


"Until now we didn't investigate the relationship between the food that is going to our mouth and what we think about it," says Peter Barham, a physicist at the University of Bristol in the United Kingdom and co-editor from the online scientific journal Flavor (Flavourjournal.com).

“We have gone from studying the physical and chemical properties of food to understanding the psychology and neuroscience of perceiving and enjoying food,” says Gordon M. Shepherd, a neurobiologist at Yale University, who publishes Neurogastronomy.




Chemistry of the Brain


Sight


When we eat the first thing that comes into play is sight. The vision predisposes, prepares and produces expectations of what will be tasted from past experiences.

“The shape and colour we perceive from the food are basic to guide the brain. And they prepare the second fundamental element, smell, which is also the most potent of the five senses and the one that is most related to emotions - explains Miguel Sánchez Romera, the only neurologist in the world who is also a chef awarded by the Michelin Guide.

For instance, chocolates with round shapes were expected to be sweeter, less bitter and more creamy than angular-shaped chocolates. (3)

But perception can also be manipulated. Professor Francisco Javier Cudeiro Mazaira, Teacher and Researcher at the University of a Coruña, recalls an anecdote in his book "Paladear con el cerebro" (recommended here). He tells that a reputed chef in an English restaurant found a few years ago how important the sight was when eating. He invited a group of diners, to whom he offered meat steaks that they savoured in the most complete darkness. The cook was asking them and everyone answered that they were delicious, very juicy. In the midst of that widespread enjoyment, the chef turned on the light and the diners ended up vomiting. They discovered, horrified, that the flesh was blue, after applying a dye. That caused them disgust.

Also, another study carried out by George H Van Doorn, Dianne Wuillemin and Charles Spence in 2014 demonstrated that the colour of a container influences people’s ratings of the taste/flavour of a warm beverage. They investigated whether consumers’ perception of a café latte beverage would be influenced by the colour (transparent, white or blue) of the mug from which it was drunk. (4)


Smell


Between 75 and 95 % of what we commonly think of as taste actually comes from the sense of smell. It confirms what the sight has perceived. The odorous molecules of food sneak through the nose to the pituitary, covered with a kind of carpet of receptor cells that fix the odorous molecules, recognize them and send electrical signals to the brain.


Taste


Then there is the taste, which works very similarly to smell. The food interacts with the receptors that cover the oral mucous membranes, on the palate and tongue. There are five basic tastes, salty, sweet, bitter, sour and umami.

But the tongue is also sensitive to temperature, pressure and chemicals that are found in a large amount of food.

Food is sensed twice, first in the mouth and then in the gut. The signals that originate in the mouth are a major contributor to the reward value of food, which can lead to a decision to eat that food. Signals that originate in the gut are involved in the termination of a meal, that is, in satiety. (9)


Chemesthesis


This last group of sensations is called "chemosynthesis." A term used to describe chemical sensory irritation. Chemesthetic sensations can be grouped together under the general term “pungency” or “pungent” and include, among others, irritation, tingling, stinging, freshness, burning, prickling, and piquancy. (5)


Two characteristic examples are Sichuan peppercorns and capsaicin. Sichuan peppercorns ( you can buy them here) leave your mouth with a tingling sensation and, at the same time, curiously numb. This is due to Hydroxy-Alpha Sanshool that activates somatosensory neurons that are responsible for detecting innocuous stimuli such as a gentle touch. It produces a similar effect to local anaesthetics used to moderate pain in surgery. Your first instinct after eating these dishes will be to grab the closest glass of water available to you. Interestingly, a sip of flat water after eating these dishes will produce a surprising fizziness like you might experience while drinking sparkling water.


Courtesy of Alchetron.com

Capsaicin which can be found in spicy chillies (buy here) activates sensory neurons in our mouth called thermal nociceptors. The activation of these thermal pain receptors stimulates our sympathetic nervous system, which is associated with our body’s “fight-or-flight” responses. Therefore, the characteristic increase in heart rate and sweat production due to the consumption of capsaicin-rich ingredients is due in part to the capsaicin’s role in adrenaline secretion. (6)


Also, certain combinations of oral sensations just do not work well together. For instance, Miracle fruit (miraculin, derived from berries of the West African plant Synsepalum dulcificum) is known to suppress the sour receptors and hence make whatever is tasted for an hour or so thereafter seem much sweeter than normal (e.g. a slice of lemon will taste sickly sweet). (7)



Courtesy of The Paleo Diet

Sound


"Sound is the forgotten flavour sense," Charles Spencer said in a study published in 2015 in Flavor magazine and, since then, has always been cited as a reference when addressing this issue. Something, of course, companies in the food sector have long been aware.

But, Is sound more important than smell? It may seem strange, but a 2007 study by the University of Leeds says that in an experiment with bacon sandwiches, showed that bacon more or less crunchy was the determining factor when assessing the quality of the sandwich. Today, consciously and unconsciously, we create a direct link between crispy and freshness. (8)

The sounds that are generated while biting into or chewing food provide a rich source of information about the textural properties of that which is being consumed, everything from the crunch of the crisp to the crispy sound of lettuce.









References


(1) Michelle Warwicker (2013). BBC. Por qué nos disgustan ciertos alimentos. [ESP]. Accessed 05 February 2020

(2) ABC Science (2011). Why do some people hate the taste of broccoli?. Accessed 05 February 2020

(3) Qian Janice Wang, Felipe Reinoso Carvalho, Dominique Persoone & Charles Spence (2017). Assessing the effect of shape on the evaluation of expected and actual chocolate flavour. Accessed 15 February 2020

(4) George H Van Doorn, Dianne Wuillemin & Charles Spence (2014). Does the colour of the mug influence the taste of the coffee?. Accessed 14 February 2020

(5) J. Enrique Cometto-muñiz (2013). Chemical Sensory Irritation or Chemesthesis. Accessed 14 February 2020

(6) Anthony Martin (2016). Discover Magazine. Sanshool Seduction: The Science of Spiciness. Accessed 15 February 2020

(7) Charles Spence, Qian Janice Wang & Jozef Youssef (2017). Pairing flavours and the temporal order of tasting. Accessed 15 February 2020

(8) Charles Spence (2015). Eating with our ears: assessing the importance of the sounds of consumption on our perception and enjoyment of multisensory flavour experiences. Accessed 15 February 2020

(9) Mikiko Kadohisa (2015). Beyond flavour to the gut and back. Accessed 14 February 2020


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