It is not just wine that goes well with food – many other drinks are very palatable with food, and that includes non-alcoholic drinks such as tea. Even bitter coffee goes well with sweet desserts.
But as you will see, the current chemical hypothesis about how all this works, especially with wines, is pretty complex and fascinating.
The story probably starts with the role of a protein receptor found on the membranes of many cells in humans (and other vertebrate animals) – this protein is called CD36 (also known as Fatty Acid Translocase, glycoprotein IV or GP88).
The sensory role of this protein in the mouth cavity cells is considerably enhanced by the interaction of CD36 with another protein receptor called Free Fatty Acid Receptor 4 (FFAR4, aka GPR120, O3FAR1, PGR4, etc) – and this combination apparently allows 80% of humans to enjoy the taste of fat.
The “taste” of fat is still not fully regarded as a taste in its own right, but there is a body of evidence that suggests it should one day be included with the other five main taste sensations: sweet, sour, bitter, salt and umami, at least for that 80% – around 20% of people are genetically incapable of having either CD36 or FFAR4 in the right proportions to be able to taste fat.
Interestingly, the lack of functional FFAR4 receptors has also been linked to obesity and diabetes, possibly due to the inability of the body to recognise the over-ingestion of fats.
The CD36 protein is a multifunctional receptor for a broad range of ligands – substances which bind with receptors to change the internal molecular conformation of the receptors, producing chemical signals as a result.
The CD36 protein is very versatile and can react to ligands which are protein-based, such as thrombospondin, fibronectin, collagen or amyloid-beta – but importantly, CD36 can also bind with lipids or fats, and especially Long-Chain Fatty Acids (LCFA) which are found in common foods.
Although CD36 has been claimed to activate gustatory (taste) neurons in the solitary tract found in the upper cervical segments of the spinal cord, the pleasurable taste of fat generally appears to require the additional input of FFAR4.
If you have never heard of FFAR4, it should be noted that this is a recent designation of the protein GPR120 and was only conferred a few months ago. Now this is a genuinely interesting protein, not only because it is found in various parts of the digestive system, including taste bud cells, but because it also regulates the presence of the hormone ghrelin, as well as certain anti-inflammatory responses.
The production of ghrelin is what induces the sensation of hunger – and when FFAR4 detects LCFAs (in particular Omega-3 fats) in food, then this determination is one of the triggers that terminate the secretion of ghrelin.
The roles of FFAR4 in managing anti-inflammatory responses and the sensitisation of insulin are also fascinating, but not quite relevant here in this article about wines.
As mentioned, the combination of CD36 and FFAR4 proteins permits most humans to taste fat.
However, the enjoyment of eating fat is also a tactile phenomenon – basically, most humans simply enjoy not only the taste but also the texturally-smooth sensation in the mouth of chewing fatty foods, which usually leads to the over-production of saliva to assist in the primary digestion of fats.
And this is where the polyphenols of wine and other astringent liquids come into play.
Every good cook knows that the best way to balance a fat-laden salad is to add some astringent ingredient, such as vinegar, lemon juice, nuts or pickles, for example.
The theory is that oral astringents provoke a dry, cleansing sensation in the mouth, thereby counteracting the drooling amounts of saliva produced while eating fatty foods.
One suggestion of how this happens is by polyphenols binding to the proline-rich proteins (PRP) in the saliva. This reduces the lubricity of saliva and thereby provokes a drier, less fatty sensation.
Another more recent proposal is that astringent compounds can actively bind directly with the oral epithelium, and that PRPs actually protect against over-astringency by binding with the polyphenols before they react fully with the oral mucous membrane.
At this point you should know that astringency, as defined by the American Society for Testing of Materials, means “the complex of sensations due to shrinking, drawing or puckering of the epithelium as a result of exposure to substances such as alums or tannins”.
Whichever way it works, it is not that simple – one reason is that astringency is not a taste, but another tactile sensation in the mouth.
In tests, small amounts of astringent compounds were applied to the inside of the upper lip, where there are no taste buds, and then on the tongue itself – astringency was detected on the inside of the lips but not by the tongue.
Also, there is the effect of astringency itself, which is a small effect initially but actually propagates over time – and it is also possibly dependent on the amount of fatty foods ingested.
Finally, subjective responses to astringency vary very widely among people – in a small evaluation of various astringent compounds on 77 individuals, there were 20 low responders, 37 medium responses, and 20 high responders – therefore even in small groups of people, the responses to a bottle of wine are likely to vary significantly.
In any case, the astringency of wine is quite probably a function of the turbidity caused by the binding of wine polyphenols to the PRPs in saliva – turbidity in this context is the development of a hazy solution of polyphenols and proteins in the mouth cavity.
A curious phenomenon is how wine is initially perceived by the palate. The initial exposure to the polyphenols from a wine does not have any immediate major astringent effect – the main impact comes around 10 to 15 seconds after initial ingestion.
This impact actually fades quite quickly too, but on subsequent sips of the wine, the astringency effect is promoted ever faster and stronger after each sip, before fading again.
So if you are consuming a lot of fatty foods, then the increasing astringency effect of wines over the course of a dinner can mitigate excessive salivation and allow you to enjoy the food better – and probably also induce you to eat a little more fat than you should.
This may turn out to be quite ironic – the reasons why perception of astringency increases over multiple exposures to the same compounds are somewhat unclear, but it is feasible that it is part of an evolutionary self-protection system. Many naturally astringent foods can cause digestive issues when over-consumed; for examples, sour fruits, unripe nuts, raw roots, etc.
Therefore the increasing astringency may actually be a signal to stop overeating such food.
Strong alcohol is also a powerful astringent, which explains why some people like a schnapps or a digestif after dinner, possibly to remove vestigial fatty flavours in the mouth.
A uniquely human experience
An obvious but underappreciated fact is that drinking wine with food is uniquely a human experience. No animals cook their foods like humans, and certainly they don’t process grapes into wines like humans.
It is a fantastic accomplishment that our species has developed the ability to elevate our enjoyment of cooking to ever greater heights by the inclusion of wines with food, thereby improving our quality of life immeasurably, at least in the Western world.
This of course also applies to other drinks, such as tea, beers, soft drinks, etc – but at the moment, the focus is on wines, so please bear with me.
In my limited experience, the usual classic choices presented at restaurants are red wines with red meats and white wines with white meats and seafood – and generally they are fine recommendations.
Regarding liver and offal, a good sweet white wine would blend well with the bitter-ish flavours – it need not be an expensive Sauternes, as some good German winter wines suit well too. For Asian foods, my preference would be to stick with tannin-rich Chinese tea, though if you can find it, a striking Grüner Veltliner may help with its mild peppery-spice nature.
With cheeses, there is some contention among gourmets as to whether strong, creamy cheeses are better with sweet white wines rather than red.
However, if one is not sure about the wine with a cheese, then my subjective suggestion is to include a little sweet chutney, honey or jam with the cheese on a piece of French bread, and have that with a red wine.
This is something learnt from the North Germans. They have been known to dribble some honey on the somewhat staid cheeses from the region.
Then it actually doesn’t matter whether the wine is red or white – though my preference is usually for the reds.
How this trick with combining sweet and cheesy flavours works with both types of wines may be the subject of another article.
As a little piece of trivia, the tradition of offering a toast to people for good health or other good wishes came originally from the Romans – at gatherings, they would toss over-toasted bread into wine to improve the taste of the rather poor wines they had at the time, and then cheer while drinking the dubious concoction.
So, no matter how bad you might think some modern wine is, it would be infinitely better than anything which was deemed to be improved by burnt bread!