In Asia it is not uncommon to eat fruit with salt or even soy sauce. From my own experience, and via friends, I known that fruits such as mango, guava, honey dew melon, watermelon, nashi pears and papaya are eaten with salt. Interestingly salt is used both for ripe and unripe fruit – the latter is especially the case for mango and guava. With unripe fruit I can imagine that the primary motivation is reduction of bitterness. I’ve previously blogged about salt and coffee and how salt in tonic water reduces bitterness – the mechanisms are the same. In addition to the bitterness suppression low concentrations of salt will enhance sweet taste. [1] This would certainly be an advantage in unripe fruit. In ripe fruit there is hardly any bitterness left (or at least I presume that is the case), so here the salt may serve a different funtion. Could it be to balance the sweet taste and give a more savory and complex flavor? Perhaps it could also be explained as increased sensing by contrast amplification?


Nashi pears (Asian pears) are delicious when served in a bowl of salty water!

One particular combination of fruit and salt that I remember from growing up in Taiwan is eating slightly unripe guavas with a beige powder. We would either sprinkle the powder onto the fruit or simply lick it from our hand. The powder had a savory flavor and was a little salty. I can’t remember the name, but from a couple of google searches I’m quite sure that it was a dried plum powder – li hing mui (or just li hing). I see that it’s available from several sellers on Amazon (In fact I just ordered a pack from Hawaii – if it’s the same I used to eat with guavas as a child it will bring back a lot of memories when it arrives!). I found a couple of blogs showing guava with plum powder and masala salt which suggests that there are probably several spice powders used together with guava. The Wikipedia entry on guavas also mentions them being eaten with soy sauce and vinegar (occasionally with sugar and black pepper) on Hawaii, and with a pinch of salt and cayenne powder/masala in Pakistan and India.

Guavas taste even better with a salty/savory dip! For the picture I combined ground star anis with salt and sugar.

As I started to search for combinations of fruit and salt I was overwhelmed by all the different combinations I found. Salt (and other salty food items) are often mixed with other ingredients such as chili or lime. Here’s a small selection of what I found in no particular order:

salt + sugar + chili (Prik-kab-klua)
salt + sugar + chili + lime (Muối ớt)
salt + chili sauce
salt + masala
salt + cayenne
soy sauce
soy sauce + vinegar (+ salt/pepper)
fish sauce
fish sauce + sugar + chili
fish sauce + black pepper
tajin = salt + chili + lime juice
kiam-muy-hoon/kiamuy
li hing mui (dried plum powder)
dried plum powder + sugar
bagoong (salted shrimp paste)
prosciutto
…

One of the few many salt + fruit combinations that has made it to Europe: prosciutto ham with honey dew melon (and some drops of balsamico syrup)

Other more specific fruit/salt/savory combinations I found were:

bananas and guavas with salt and fresh pepper (served in India)
chili salt with fruits such as Granny Smith apples, plums or oranges.
peaches with chili/lime/salt
pomelos with salt and red chillis
Hawiian margarita with Ling Hi Mui powder
…

It seems that eating fruit with salt is far more common in warm countries where an additional intake of salt is recommended due to perspiration. (Update: Lisa comments on her Swedish blog that it could be due to the fact that there are more supertasters in Asia – they are more sensitive to bitterness, hence the additional use of salt) And I admit that my craving for salt does increase when it’s warm. But there is more to this than physiology – the few combinations I have tried are indeed mouth watering – even when tested in cold Norway. And thinking about it, it is really fascinating how plain table salt – one of the simplest (chemically speaking) ingredients we have in the kitchen – has such a repertoire in combination with fruit. There is certainly a lot to try out in the kitchen now – and perhaps some inspiration from Asia for chefs as well?

If you know about or have tasted other fruit + salt combinations, please leave a comment in the section below

Reference:
[1] Keast, R. S. J.; Bresling, P. A. S. “An overview of binary taste-taste interactions” Food Quality and Preference 2002 (14), 111.

I prefer my coffee black, and politely decline when offered milk and sugar. However, if offered salt I would probably smile and say “Yes, please!” Salt???! It turns out that adding salt to coffee is not as weird as it may sound at first. There is a tradition for adding a pinch of salt to coffee in Northern Scandinavia, Sibir, Turkey and Hungary. And when available, such as in coastal areas where fresh water from rivers mixes with the salt sea, one would simply use brackish water when preparing coffee. This water typically has a salt content of 0.5-3%, which is lower than the average 3.5% in seawater. This results in a more intense taste and more foaming. And if living far from the sea, the Swedish food blogger Lisa Förare Winbladh let me know that in Northern Sweden one would deliberately add salt if using melt water from glaciers for making coffee. But tradition aside, is there a scientific explanation of this widespread tradition of preparing coffee with addition of salt?

The first thing that comes to mind is that salt reduces bitterness. And to be more precise it is the sodium ion (Na⁺) that interferes with the transduction mechanism of bitter taste. But interestingly the mechanism behind this is not fully understood! One of my very first blog posts was about tonic water and how one by adding salt can suppress the bitter taste and make tonic water more or less sweet. It’s a fascinating experiment that you should try at home. Expect to use about 1,5-2 g salt for a glass with roughly 1,5 dL (150 g) of tonic water. It’s a good idea to start with a little salt and taste it as you go.

Try adding a little salt to tonic water – the effect is quite surprising: The characteristic bitterness from the added quinine disappears!

Bitterness is an important flavor in coffee, but under less-than-optimal extraction conditions it can be too dominant. Generally bitter tasting compounds are less water soluble than other coffee flavors, hence the bitter compounds are extracted towards the end of the brewing. High temperatures (close to boiling) and long extraction times also favor bitterness. In that respect the coffee percolator is known to produce rather bitter, over-extracted coffee due to near boiling temperatures, and such coffee would most likely benefit from a little salt! And before the percolator came the ground coffee was just put into the boiling water and then left to settle. I can really imagine how brackish water could actually benefit

But the salt need not be reserved for over-extracted coffee. I’ve tried using salt both in a drip coffee maker and in the filter basked when pulling an espresso. The tests were very un-scientific, but the tiny amount of salt does dampen bitterness and change the coffee taste (but the coffee does not have a salty taste). Since I lack cupping experience, I certainly lack the language to describe how salt influences the taste, so I leave it up to you to try it out! And maybe some baristas with cupping experience can fill me out on this and do some tests?

In stead of just using plain salt with coffee, cured ham would signal rafinesse if served in central Europe, whereas in Northern Sweden there is a tradition for serving dried meat with coffee. The Swedish author Mikael Niemi describes this in his novel Popular music from Vittula:

“… and then the pièce de résistance among all the sweetmeats: a hard, brown lump of dried reindeer meat. Salty slices were cut and placed in the coffee, chunks of coffee-cheese stirred in, and white sugar lumps were held between the lips. And then, fingers trembling, we all poured the coffee mixture into our saucers, and slurped our way to heaven.”

With cured ham, apart from the salt-coffee interaction, one also has the combination of meat and coffee. From previous flavor pairing rounds TGRWT #1 and #5 (chocolate/coffee and coffee/meat respectively) we have seen that coffee and meat in some ways approach each other and are actually a good combination. A secret tip BTW is to add a little coffee to your beef stocks for extra depth and richness – this works because coffee shares many impact flavors with browned meats due to the Maillard reaction.

Now I’m curious – are you aware of coffee-salt combinations in your own country? Please tell me about it! And if you try a pinch of salt in your coffee – how did it taste?

Update: Read about my tests of coffee with salt at Tim Wendelboe’s coffe shop

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Some articles that discuss the role of sodium ions (Na⁺) in suppression of bitter receptors:

Breslin, P. A. S; Beauchamp, G.K. “Suppression of Bitterness by Sodium: Variation Among Bitter Taste Stimuli” Chemical Senses 1995, 20, 609-623.

Breslin, P. A. S; Beauchamp, G.K. “Salt enhances flavour by suppressing bitterness” Nature 1997 (387), 563.

Bresling, P. A. S “Interactions among salty, sour and bitter compounds” Trends in Food Science & Technology 1996 (7), 390. (free download)

Keast, R. S. J.; Breslin, P. A. S. “An overview of binary taste–taste interactions” Food Quality and Preference 2003, 14(2), 111.

In addition to suppression of bitterness, salt can enhance sweetness at low concentrations and umami flavors at higher concentrations (more about this in part 5 of “Practical tips for molecular gastronomy”).

When invited over to friends for dinner, even before eating, you judge the food by it’s aroma, handing out compliments such as “It really smells nice”! Thankfully, nature is on the cook’s side, because when we prepare food and heat it, volatile aroma compounds are released which trigger very sensitive receptors in our noses. It is generally said that 80% of “taste” is perceived by our nose (what we refer to as aroma), whereas only 20% is perceived by our tongue. How important smell is becomes clear if you catch a cold – suddenly all food tastes the same. Too illustrate the importance of smell, prepare equally sized pieces of apple and pear. Close your eyes, hold your nose and let a friend give you the pieces without telling which is which. Notice how difficult it is to tell them apart. In fact, with a good nose clip you wouldn’t even be able to tell the difference between an apple and an onion! Then, with a piece of either in your mouth, let go of your nose. Within a second you can tell whether it’s apple or pear!

Taste
Our tongue has approximately 10.000 taste buds and they are replaced every 1 to 3 weeks. Their sensitivity increases roughly in the following order: sweet < salt < sour < bitter. In addition to the four basic tastes there is umami, the savory, fifth taste. This taste is produced by monosodium glutamate (MSG), disodium 5’-inosine monophosphate (IMP) and disodium 5’-guanosine monophosphate (GMP). Pure MSG doesn’t taste of much, but can enhance the taste of other foods. There are also some claims of a sixth taste.

A number of taste synergies/enhancements exist. I’ve also included three examples of how flavours can influence taste:

The only general, over-all trend which can be found is that binary tastes enhance each other at low concentrations and suppress each other at higher concentrations (but there are several exceptions!). Do check out “An overview of binary taste–taste interactions” (DOI:10.1016/S0950-3293(02)00110-6) if you’re interested in more details on binary taste interactions. I’ve tried to visualize taste enhancements (green) and suppresions (red) in the following figure using arrows to indicate the direction. For example, salt suppresses sweetnes at high concentrations.

In addition to taste, our tongue also percieves texture, temperature and astringency. An interesting thing about the temperature receptors is that they can be triggered not only by temperature, but also by certain foods. The cold receptor is triggered by mint, spearmint, menthol and camphor. There is even a patented compound, monomenthyl succinate, that triggers the cold receptor, but without the taste of menthol. It’s marketed under the name Physcool by the flavour company Mane.

Substances such as ethanol and capsaicin trigger the trigeminal nerve, causing a burning sensation. Capsaicin also triggers the high temperature receptors of the tongue, hence the term “hot food” which can refer both to spicy food and food which is very warm. For a general article about taste, check out “Taste Perception: Cracking the Code” (DOI:10.1371/journal.pbio.0020064, free download).

Flavour
Our nose has about 5-10 million receptors capable of detecting volatile compounds. There are about 1000 different smell receptors and they allow us to distinguish more than 10.000 different smells – perhaps as many as 100.000! In order for us to smell something, the molecule needs to enter our nose at a concentration sufficient for us to detect. Aroma compounds are typically small, non-polar molecules. The fact that they are small means they will have low boiling points – they are volatile and spread rapidly throughout a room. They are often referred to as essential oils and are very soluble in fat, oil and alcohol. These aroma compounds generally not soluble in water, but there are also water soluble aroma compounds; just think of a well prepared stock – no fat but lots of taste and aroma!

A challenge with aroma molecules is that they should remain intact during storage and not be released until cooking (or even better, until consumption). A example would be to install a Liebieg condenser over your pot. Dylan Stiles has explored this in his column Bench Monkey by placing a bag of ice on top of the lid. He claims that his roommates prefereed the curry which has been cooked under “reflux conditions”. The study was performed in a double blind manner (which I will come back to in part 8 of this series).

Because aroma compounds are volatile, spices should be obtained whole and stored in tight containers away from light. If possible, fresh herbs should be used. The flavour of herbs and spices can be extracted by chopping or grinding to increase the surface area. To speed up grinding in a mortar you can add a pinch of salt or sugar.

Heat can help extract flavour (just think of how we brew tea or coffee), but will also evaporate volatile compounds, so a general advice would be to add spices at the start and herbs towards the end of the cooking time. Some herbs can even be sprinkeled over the food just before serving. In Southeast Asia (and especially India) it is quite common heat spices in a dry pan or in oil. This matures flavours and allows reactions to occur (possibly Maillard reactions). Coarse spices should be added earlier than finely ground spices.

In addition to adding flavour using spices, herbs and other foods, we can also use heat to create new flavours. When sugar is heated, caramel is formed. And if a reducing sugar is heated in the presence of an amino acid, they react and form a host of new flavour compounds in what is known as the Maillard reaction. Caramelisation and the Maillard reaction are known as non-enzymatic browning. Enzymatic browning on the other hand is detrimental to many fruits (such as apples and bananas), but there are a few exceptions. Enzymatic browning is essential in the production of tea (black, green, oolong), coffe, cocoa and vanilla, although this is rarely attempted in kitchen.

Another source of flavour is fermentation. It refers to a process were sugar is converted to alcohol and carbon dioxide by the action of a yeast. In the process a number of flavour compounds are formed as well which is why this is of great interest also from a molecular gastronomy viewpoint. Some examples of fermented products include wine, beer, cider and bread. Fermentation also refers to the process where some bacteria produce lactic acid. Some examples of foods resulting from lactic acid fermentation are yoghurt, kimchi and pickled cucumbers.

Flavour pairing
Cookbooks and recipes throughout the world are the result of billions of experiments. As a result, some very good combinations of herbs and spices have been discovered. Some of these mixtures have even been given names of their own and it is fascinating how easily one can forget that curry for instance is a mixture of spices. Wikipedia has a wonderful overview of herb and spice mixtures from all over the world. I must admit I only new a fraction of these:

Adjika | Advieh | Berbere | Bouquet garni | Buknu | Cajun King | Chaat masala | Chaunk | Chermoula | Chili powder | Curry powder | Djahe | Fines herbes | Five-spice powder | Garam masala | Garlic salt | Harissa | Herbes de Provence | Khmeli suneli | Lawry’s and Adolph’s | Masala | Masuman | Mixed spice | Niter kibbeh | Old Bay Seasoning | Panch phoron | Quatre épices | Ras el hanout | Recado rojo | Shake ‘N’ Bake | Sharena sol | Shichimi | Spice mix | Tajín | Tandoori masala | Tony Chachere’s | Za’atar

A book which I’ve found to be very useful when combining flavours is “Culinary artistry” by Andrew Dornenburg and Karen Page. It is the most comprehensive book about flavour pairing that I’m aware of, and I would say it is indispensible for someone who likes to cook without a cookbook. It has lists of basic flavors contributed by various foods. For example a sweet taste is contributed by foods such as bananas, beets, carrots, coriander, corn, dates, figs, fruits, grapes, onions, poppy seeds, sesame and vanilla (plus sugars and syrups of course). It has lists of “flavor pals”, a term attributed to Jean-Georges Vongerichten. For example, the flavour pals of ginger are allspice, chiles, chives, cinnamon, cloves ,coriander, cumin, curry, fennel, garlic, mace, nutmeg, black pepper and saffron. By far the most extensive part of the book are listings of food matchings. An illustrative example is pork which combines well with (classic/widely used combinations in bold):

apples, apricots, bay leaves, black beans, beer, brandy, cabbage, Calvados, dried sour cherries, clams, Cognac, coriander, cream, cumin, fennel, fruit, garlic, ginger, hoisin sauce, honey, juniper berries, lemon, lime, marsala, molasses, mustard, onions, orange, parsley, black pepper, pineapple, Chinese plum sauce, plums, prunes, quinces, rosemary, sage, sauerkraut, soy sauce, star anise, tarragon, thyme, vinegar, walnuts, whiskey, white wine

Despite the abundance of combinations, I dare say that little is understood about the science behind these flavour pairings. Why do these combinations of herbs and spices go particularily well together? Is it all about getting used to the combinations, so that we learn to like them? What influence does the complexity of the flavour play? These are easy questions that probably have rather complex answers.

Very recently a different approach to flavour pairing has emerged. If two foods share one or more key odorants, chances are that they will go well together. The first step towards finding new pairings would be to identify key odorants. More info on key odorants can be found in the article “Evaluation of the Key Odorants of Foods by Dilution Experiments, Aroma Models and Omission” (DOI: 10.1093/chemse/26.5.533, free download). I’ve initiated the food blogging event “They go really well together” (TGRWT) to explore new flavour pairings and develop new recipes. There are also several blogposts with interesting comments on about flavour pairing.

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Check out my previous blogpost for an overview of the tips for practical molecular gastronomy. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

A very simple chemical that neutralized/modifies bitter taste is salt – and the best thing is that you don’t have to be a supertaster to test this. For a simple experiment, take tonic water, taste it and then stir in some salt (start with 1/2 teaspoon). Taste it again – if you can still taste the quinine, add a little more salt. At one point the bitter taste has almost disappeared! This principle might work for cucumbers and melons as well, but of cource there could be totally different taste mechanisms responsible for the bittertaste in the two cases.

It might sound strange to add salt, but in Asia, it is not uncommon to eat different fruits with salt. I am aware of unripe mangoes, guavas and honey dew melon are eaten with salt, a salty spice and soy sauce respectively. Also – some people add a small amount of salt to the water when brewing coffee – this reduces bitterness and rounds of the taste. One last example is how salty food can make a young red wine with plenty of tannins more pleasent to drink. Tannins (polyphenolic compounds) can be both astringent and bitter, depending on their molecular weight (low molecular weight tannins are predominantely bitter whereas larger molecules are more astringent).

BTW, this has also been treated scientifically. See for instance: Breslin, P. A. S; G.K. Beauchamp, “Suppression of Bitterness by Sodium: Variation Among Bitter Taste Stimuli” Chemical Senses 1995, 20, 609-623 (link).