How the simplest ingredient can revolutionize food
a bit of food science
When embarking on an exploration journey around ingredients and cooking, what better place to begin with than the omnipresent salt? You can find salt in any recipe (often even sweet ones). If not explicitly written, the recipe's author may have assumed you will add salt at some point or some salty ingredients will provide enough salt to the dish.
Mined from the ground or dried from the sea, salt is a central figure of human history1. Initially, it was mainly used for food preservation, as high concentrations of salt prevent microorganism growth. But soon enough humans discovered another superpower of salt: a transformative role in flavor.
We often think of “flavor” as the sensation the tongue feels when a spoonful of food reaches the mouth, but it is much more than that. Flavor comprises a handful of simultaneous phenomena. One of them, taste, does start on the tongue. Specifically, receptors in the tongue, soft palate, and upper esophagus sense salty, sour, sweet, bitter, or umami molecules and convey the corresponding signals to the brain. But flavor also (actually, mainly) encompasses aromas, which are sensed through smell. When food moves around in the mouth, volatile compounds are released and travel from the back of the mouth to the olfactory receptors in the nasal cavity (the same receptors that detect the smell of a flower). The resulting olfactory sensations are thought to account for 70-90% of flavor2. This is why the loss of the sense of smell, a frequent occurrence associated not only with COVID-19 but also with other infections or conditions, impacts profoundly food enjoyment. Finally, texture and other chemosensory properties, such as the pain sensation elicited by capsaicin in spicy peppers or the cold sensation conveyed by menthol, are also considered components of flavor.
But how can salt influence flavor? First, through its intrinsic taste. When salt (the most common being sodium chloride) meets saliva, it dissociates into two types of ions (charged atoms): sodium (Na+) and chloride (Cl-). Sodium ions then enter the cells of the mouth through epithelial sodium channels. The flux of these positively charged ions to the intracellular space initiates a signal that travels to the brain and elicits the sensation of saltiness3. This is the best-characterized mechanism behind the taste of salt, but the complete mechanism is yet mysterious and thought to involve other groups of receptors4.
Besides imparting its own taste, salt can skew the flavor of a dish to a more pleasant one. While some mechanisms for this are still puzzling scientists and tasters, others are starting to unravel. Namely, salt can improve flavor by suppressing bitterness or emphasizing aromas.
In a pioneering experiment, Kroeze and Bartoshuk observed that if salty and bitter compounds were added to separate tongue regions, volunteers sensed both saltiness and bitterness. However, if those compounds were placed on the same tongue region, bitterness was reduced5. Thus, it is thought that salt’s sodium ions can block the transmission of bitter taste signals before they reach the brain. By reducing bitterness, salt can make pleasant tastes and aromas more perceptible6. This is likely behind the success of products like sea salt dark chocolate or salted caramel, where salt flakes not only lend some crunchy texture but also suppress cocoa or caramel bitterness while emphasizing and balancing sweetness. (see some ways to test bitterness suppression yourself at the end of the post)
Salt also impacts flavor by potentiating aromas. One of the ways this happens is through a “salting out” effect, in which the presence of salt decreases the solubility of volatile odorant compounds, making them more available to travel through the back of the mouth and reach the olfactory receptors7. Furthermore, when salt is added on top of food, it can draw water out through osmosis (when water molecules travel from a low- to a high‑concentration medium to reach equilibrium). This dehydration increases the concentration of aroma compounds inside the food. This occurs, for example, when you salt a fresh tomato before serving it. The high concentration of salt sprinkled on the surface promotes water release from inside the tomato, where flavor gets concentrated. The same flavor concentration due to dehydration applies to slow-roasted or sun-dried tomatoes. Naturally, this will be most noticeable with ripe in‑season tomatoes, which actually have some flavorful molecules to be concentrated.
Finally, studies suggest that salt can improve food texture by increasing thickness perception (for example, in a soup). The mechanism for this is unclear, but one possibility is that, besides taste receptors, salt activates touch neural paths 4.
By balancing bitterness and sweetness, elevating aromas, and increasing the dimensions and complexity of food, salt can thus be an asset for both savory and sweet preparations.
While salt gets a bad rap due to the association of high-sodium diets with health issues, most of the sodium ingested in these diets comes from processed foods, which have extra sodium for preservation, flavor, or other processing purposes. Various simple low-sodium foods, like peas or sweet corn, have much higher amounts of sodium post-processing8. In any case, while salt can be key to avoiding blandness, you can spare some of it by using other ingredients to build flavor and complexity:
Prioritize local and seasonal ingredients, which naturally have more flavor than ingredients that have traveled a lot or are out of season.
Build flavor and complexity by adding salt through salty ingredients, like anchovies, soy sauce, cheese, olives, or capers. These ingredients dispense the need for much additional salt and come with bonus flavor. Some of them are also packed with umami, which may enhance flavor even in low salt conditions 8.
Boost flavor by adding herbs, spices, or acidic ingredients.
All in all, some practice is required to achieve the “bliss point”. While salt increases the likeability of food, it does so only up to a certain point, from which food merely becomes salty. Use your power to taste. Tasting while cooking helps in understanding how each ingredient impacts flavor. If food feels bland, take a spoonful and add a pinch of salt. Keep tasting. With time, confidence and flavor will make it to the menu.
Try it yourself
Rocket leaves
Do you happen to like rocket leaves in some contexts but not others? Eaten by themselves, rocket leaves can taste very bitter, but in other contexts, such as a well-seasoned salad or on top of a pizza, they may give a nice touch to the dish. This is because salt can reduce the bitterness of rocket leaves.
Experiment: Season some rocket leaves with only olive oil and vinegar. Taste. Then, add salt. Taste again. Did you notice any change in bitterness?
Grapefruit
For many, grapefruit is not something to eat like an orange or a clementine, as it is very bitter. Turns out salt can make it better!
Experiment: Peel a grapefruit and take off two buds (even better if you remove the thin whitish skin). Sprinkle one with a good pinch of salt. First, try the one without salt. Let the bitter flavor subside. Then, try the other. Did the bitterness reduce? Maybe you will also like it in a well-seasoned salad!
M. Kurlansky, Salt: a world history, New York: Penguin Books, 2003.
Spence, C. Just how much of what we taste derives from the sense of smell? Flavour 4, 30 (2015). https://doi.org/10.1186/s13411-015-0040-2
Jackson, R. S. (2002). Taste and mouth-feel. Wine Tasting, 79–111. doi:10.1016/b978-012379076-7/50006-6
Institute of Medicine (US) Committee on Strategies to Reduce Sodium Intake. Strategies to Reduce Sodium Intake in the United States. Henney JE, Taylor CL, Boon CS, editors. Washington (DC): National Academies Press (US); 2010. PMID: 21210559.
Kroeze JH, Bartoshuk LM. Bitterness suppression as revealed by split-tongue taste stimulation in humans. Physiol Behav. 1985 Nov;35(5):779-83. doi: 10.1016/0031-9384(85)90412-3. PMID: 4080842.
Breslin, P., Beauchamp, G. Salt enhances flavour by suppressing bitterness. Nature 387, 563 (1997). https://doi.org/10.1038/42388
Salles, C. (2006). Odour–taste interactions in flavour perception. Flavour in Food, 345–368. doi:10.1533/9781845691400.3.345
Liem DG, Miremadi F, Keast RS. Reducing sodium in foods: the effect on flavor. Nutrients. 2011 Jun;3(6):694-711. doi: 10.3390/nu3060694. Epub 2011 Jun 20. PMID: 22254117; PMCID: PMC3257639.