This is a really well-presented discussion of a sometimes-difficult topic! Personally I enjoy the technical side of cooking (breads, custards, time and temperature control, and so on) while my wife has much better flavor intuition. My brother in law called us The Reasoning and The Seasoning at our wedding.
When I was in grad school I bought a book called The Flavor Bible. Literally they just asked a bunch of chefs "What goes with X?" for a bunch of different X, and published the resulting lists, plus some annotation for what was a particularly popular or classic pairing. It's the only food-related book I brought with me when I downsized to live in an RV. I still consult it sometimes when I'm stumped.
And yeah, tangzhong is an excellent choice for better cinnamon roll texture. I tried it for the first time this past Christmas. Sadly I had to throw them all out, and the frosting, and a few other baked goods, because there was something wrong with the coconut sugar I'd used. I could totally see a five-spiced version (probably less gooey than I usually make) served alongside a Thai sweet chili chicken.
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(This one's a double-header on the tightly-linked senses of smell and taste, especially pertaining to foodcraft; it comprises both The Space of Olfaction is δ-Hyperbolic and A Partial Theory of Flavor Pairing in Foodcraft. You could read them in either order. I've chosen to put the more widely-appealing one about food phenomenology first and the less polished and more abstract and speculative one about olfaction second. Dedicated to SR-S and SS on the occasion of their marriage, and to the whole S family, who has already begun to benefit from this theoretical depth. Enjoy the sixspice buns!)
(Part 1: Theory of Foodcraft. Epistemic status: only partially worked out, lots of handwaving, still not something I've seen talked much about explicitly anywhere.)
(With thanks to @johnswentworth, @Morphism, @WhatsTrueKittycat, and MR and RG of Mox, among others, who all asked for this. If you asked me for this out of the list, it's also for you.)
Food and drinks have flavors [citation needed]. In fact, they have lots of flavors - careful tasting of an ordinary bottled barbecue sauce presents sweetness and tartness and savoriness, and beneath those, tomato and molasses, and beneath those - if you get that far - mustard seed and paprika and onion powder and "some kind of fish sauce???". (It's Worcestershire sauce.) Some flavors blend nicely, like onion and garlic, while others clash, like onion and pineapple. But then some very different flavors pair just fine, like apples and cinnamon, or vanilla and nearly anything you'd find in a dessert. And even onion and pineapple go together just fine in the greater context of a salsa, or even a pizza! So what's going on?
Here's a stab at explaining why. I'll use "food" as a term of art to mean anything intended to be eaten and enjoyed. A food flavor is comprised of two major parts: its tastes (sweet, salty, spicy, all the basic and chemosensory types) and its flavors (individual odorants, mostly associated with specific ingredients like cumin, tomato, or beef). On top of that, we have things like its context (what's the nature of the larger mixture? is it a dessert? a stew?), its temperature, and the relative concentration of flavors, and to a lesser extent modifiers like how cooked it is (caramelized, raw, normally cooked as "blurs out and turns up the gain" on flavors), what solvent it's in (water, alcohol, fat), the physical properties of the substrate (is it crunchy? soft? liquid?), and what expectations you have when tasting the food.
On my model, a combination of flavors tastes at least OK if at least one of three things is true, and generally better with more of them satisfied. The combination can call back to a known tasty food, it can have satisfying blending with no bad clashes, and it can have interesting bistable contrasts with indepdently good-but-maybe-overstrong components.
The first of these, the Rule of Familarity, is the simplest to explain. A food will probably taste OK if the flavors in it match closely to the major notes of a known and beloved dish and the presentation of the food isn't too terribly different. This is the operating principle behind any fussy "deconstructed" food: you take the components of a dish and permute or alter their order or presentation while leaving the basic notes intact, as well as the general presentation. Maybe you also really sell the phenomological binding by adding some additional element that would classically go with the dish, just to control expectations a little. Take the example of a deconstructed apple pie. Turn the apple filling to a reduction sauce and swap crust for an artful bed of crumbs. Make very sure that the apple sauce has a bit of molasses and cinnamon in it, maybe some other pie spices. Apple pie's easy for presentation, since it's served both hot and cold, but if you really want to sell the effect, serve it with the sauce piping hot with a scoop of vanilla ice cream alongside. It'll be... fine. Sell it for 30 bucks a plate. (Give me a proper slice of pie any day, though.) Almost every food can be done up this way - dishes have major ingredients that people will expect, expected form factors or temperatures to serve them at, and expected roles that need to be filled. Match those well enough and you probably end up with something good.
The second, the Rule of Harmony, is a little trickier: there is a need for satisfying blending. A food will probably taste OK if any given pair of flavors in it blend satisfyingly, and no pair of ingredients clashes. On this model, a pair of flavors blends well if they share flavor chemicals; the more, the better the blend. Thus: onions and garlic, vanilla and most (but not all!) sweet flavors, and meat with anything savory, like tomato. This also helps explain what's going on with spices: they're almost pure flavor, and frequently contain flavorant chemicals that they share in common with ingredients. This in particular is why vanilla and chocolate see such wide appeal, and why rose was once the standard for desserts before vanilla: their chemical makeups are exceedingly complex and multifaceted, having some degree of commonality with a wide variety of different ingredients. This is also why oak is used for wine casks: it too contains vanillin. Alternately, we might contrast the sense of "blending" here with "masking", where "masking" should be taken to mean an attempt to force a fit by moving as far as possible to one extreme of the bistable spectrum; this rarely works out well. For instance, certain intoxicatingly herbed pastries frequently contain lots of chocolate in a doomed attempt to mask the taste. Better to work with the terrain rather than against it, to blend the flavor in instead - from personal experience I can recommend a nice quiche Florentine, whose heavy spinach component blends much better with bitter green flavors, especially alongside the base of pleasantly sulfurous Gruyere cheese and eggs, with onions, garlic, and perhaps some bacon all indicated.
Lastly, the Rule of Interesting Contrasts. A food will probably taste OK if it has some kind of interesting bistable contrast in it and it's made of individually good-but-maybe-overstrong components - and, again, no bad clashes. By bistable here I refer to an effect that can be achieved straightforwardly with careful balances of pairs of distinct tastes or even flavors, where we note that (e.g.) with a combination of salty and sweet, at one extreme the mix is just salty, at the other it's just sweet, but at some point in between, finely graded concentration differences and habituation effects give rise to the sensation of a taste that seems to flip back and forth between the two components. This is the operating principle behind trail mix: people generally like some subset of dried fruit, chocolate, beef jerky, cheese crackers, assorted nuts, and the like. (It's also the operating principle behind any cursed combination of foods that's "surprisingly good".) Each of them hits all the expected marks for being individually enjoyable - one or more of salt, sugar, and fat; individually enjoyable flavors; pleasant texture and form factor; all that good stuff. Also, for any given pair of those, there's one or both of a difference in taste - covering both sweet and salty - and a reasonably compatible difference in flavor (e.g. meat and fruit). Here we find a deep secret of foodcraft: never neglect the acid. A little tartness is a vital component of almost any food, and I hypothesize that a part of why is its capacity to play a supporting role to contrast well with sweet, fatty, and salty alike.
As with any art, the rules are not ironclad, and they can be broken to good effect. Neither are they universal: a combination of shrimp paste and pears might disgust you, but to the Indonesian palate, it evokes delicious rojak. Another is the rule against bad clashes: on this model, the reason why onion and pineapple go just fine together in a salsa is that the onion pairs excellently with the tomato (itself arrogating the savoriness of meat, along with salt), and the pineapple serves the role of adding sweetness and tartness, supporting the salsa as a whole rather than pairing with any specific ingredient; the same is generally true of any dish where one ingredient sticks out as particularly weird, and likewise, there likely ultimately exists no pair of ingredients that cannot be made to go together somehow in some dish. From this we might posit that the rule of familarity can override some minor clashes, if one of the clashing ingredients is core to the dish, the other is serving some role, and the clash is merely not enjoyable rather than actively offensive. Conversely, the "Incompatible Food Triad" - three ingredients that go together well pairwise but not as a triple - points the way to what looks like a puzzling inconsistency, but we might resolve the seeming paradox by pointing out that in such cases, any pair of the three evokes a very different dish, with the third having no place in it at all. That said, even the foremost research into Incompatible Food Triads has failed to turn up any particularly clean or striking examples of one, the closest being yogurt, salted cucumber, and sugar - breakfast yogurt, tzatziki, and sweet pickles are each perfectly fine dishes, but they pull in very different directions.
Using the principles expounded here, you can start composing your very own dishes. My specialties are generally of this sort: I've made a delicious beef stew halfway between an English-style stew and a boeuf borguignon; I've made a variant on cinnamon buns that uses plenty of Chinese five-spice powder, on top of the use of tangzhong dough preparation, to approval from Grandma Kim and numerous friends alike; and I've swapped out the broccoli in various dishes with Romanesco cauliflower to cheers. People ask me how I think of these substitutions, but considered rightly in a frame that this post partially illuminates, they all constitute natural alterations. Go make something delicious of your own!
(Part 2: Theory of Olfaction. Epistemic status: barely even half-baked - but unique, intriguingly plausible, and anyway no one has any better ideas.)
Vision, hearing, the numerous aspects of touch, taste, and smell: of these, smell - or olfaction - is by far the worst-understood, even if we try to tease out the role that olfaction plays in flavor, separating it from the gustation and chemoception that strict-sense taste encompasses. As Convergent Research puts it, “We can’t yet replicate animal olfaction synthetically as a sensing and classification modality. We currently lack a comprehensive model explaining how biological systems decode and classify chemical signals through olfaction. Understanding this process is critical for applications ranging from flavor science to disease diagnostics to understanding and harnessing animal communication.” This past weekend, I briefly attended a “gap mapping” research hackathon organized by YJK; my thanks both to him and to DK who invited me.
While I couldn’t hope to build a full olfaction decoding model, nor fully map odorant-receptor binding, nor even give a robust and comprehensive working theory of how to replicate olfaction in the few hours I had, I thought it prudent to at least clean up my existing thoughts on the subject, given how they’re informed heavily by both my experience in geometric group theory - far removed from the life sciences - as well as my experience as a skilled home chef, sometime perfume blender, and possessor of a keen sense of smell as linked to a keener phenomenology. With any luck, the added insight from the model I sketch out of how olfaction might work will prove a useful map for others more skilled in more central approaches to the question of olfaction; I believe the model to be a plausible one, given a few established facts about both the biochemical basis and subjective experience of olfaction.
Let me start by defining some terms carefully and laying out premises in the language that those terms scaffold. I’ll use “smell” to describe a direct olfactory percept, like the experience of exposure to (+)-limonene, or to ammonia with minor adjuncts, or to a blend of citronellol, geraniol, rose oxide, and beta-damascenone. I’ll use “scent” to mean the olfactory experience a person might have on being exposed to that smell in some concentration or set of concentrations; respectively: orange, stale cat urine, and rose.
For some established facts, we first note that olfactory receptors come in many different varieties, each highly selective to a single small molecule, or to a small set of chemically similar small molecules. Additionally, every such receptor has a band of sensitivity in terms of (say) parts per billion, below which the smell is imperceptible and above which the receptor either tops out or else no longer fires at all (consider the infamous case of hydrogen sulfide); we can rescale that range to the open interval (0, 1) as a fraction of maximal perception strength. As a minor fact, chiral molecules generally smell very different from each other, and don’t cancel each other out: the scent of (+)-limonene closely corresponds to the smell of oranges, but (-)-limonene’s scent better approximates pine; (+)-carvone smells like caraway or dill, while (-)-carvone’s scent is much more like the smell of spearmint. Meanwhile, we may make two mysterious observations: that given one scent, the addition of any amount of any other scent will be smothered by it, blend with or mutate it into a different scent, or stand out against it altogether; and that when moving through a room with a single (complex) smell source present, the resulting scent perceived can nonetheless change with factors including position with respect to the source, air currents, and even different individuals’ olfactory keenness or disabilities.
My major premise is this: arbitrary combinations of smells can be observed, but any two scents built up from smells - even the same list of smells, in some cases - differ greatly from each other, and this suggests that olfaction is best understood as having a treelike or hyperbolic structure to it. (This is notably unlike audition, which may be modeled as involving something like a Fourier decomposition with some added spatial information from timing differences, and unlike vision, which may be loosely modeled as having some pixel-like structure with three-dimensional Euclidean (color) coordinates for each pixel.) In addition, just as the color gamut is limited to only a part of Euclidean space, so too is the scent gamut limited to a tiny sliver of the possible (high-dimensional) hyperbolic space, given the nonexistence of anti-scents - though the nature of hyperbolic space is such that unlike with color, we barely notice the lack.
To understand why this is so plausible, it will be necessary to explain the concept of a δ-hyperbolic space. A δ-hyperbolic space is a metric space in which for any triangle ABC that we might draw, every point on the side AC is distance at most δ from some point on one of the sides AB, BC, and likewise for the other two sides Put another way, the entirety of each of the sides is relatively nearby to the other two sides of the triangle. (This is the picture at the head of the page.) The ordinary hyperbolic plane can be calculated to be ~0.88-hyperbolic, and at δ = 0, we find trees - note that for any three points in a tree, if they’re not part of a single path, then there exists a unique vertex which all three sides of the triangle contain.
The δ-thin hyperbolic model of olfaction then goes like this:
This model suggests a few ex ante predictions/explanations and proposes associated measurements and tests..