The Xmas-to-New-Year break was excellent timing-wise for reading Flavorama. With holiday foods, tasty treats, and wonderful smells from the oven, I found myself paying attention to aromas, tastes, textures, and more. I also learned that my vocabulary for describing such sensory delights was very limited – but this can be remedied by paying careful attention and lots of practice. I haven’t done so systematically, but I believe the words of Arielle Johnson (the author), who has her PhD in analytical chemistry and did research at food labs and restaurants. She has trained many volunteers to help smell and taste experimental food products, and almost everyone can do so with practice.
Flavorama is subtitled “a guide to unlocking the art and science of flavor”. You don’t need to be a scientist to understand the science part of it. Johnson is an excellent writer with a sense of humor and knows how to explain chemistry to a non-expert. The hand-drawn figures are both excellent and informative. However, let’s not forget the art. While there are tried-and-true techniques that Johnson shares, she also provides examples of how one might explore the vast and subtle landscape of flavors – through some trial and error tempered with understanding the general principles of flavor creation and manipulation.
Did you know that your senses of taste and smell are the only ones that are sensitive enough to distinguish nanoscale individual molecules? Our olfactory apparatus and our tongue are amazing molecular-level sensors. In her introduction Johnson provides the four laws of flavor:
1. Flavor is taste and smell.
2. Flavor follows predictable patterns.
3. Flavor can be concentrated, extracted and infused.
4. Flavor can be created and transformed.
This divides her book into its four major sections. I was reminded of the laws of thermodynamics because before these laws comes the Zeroth Law that underpins everything. According to Johnson, and rightly so,
0. Flavor is molecules.
The chemist in me rejoices!
The First Law distinguishes taste and smell. The two are quite different. Tastes are almost monolithic. They’re simple. They’re baseline. The taste receptors on our tongue each have a dedicated line to tell our brain when we’re tasting one of the five: sweet, salty, sour, umami, and bitter. Sugar molecules bind to the sweet receptor. Inorganic ions (sodium in particular) activate the salty receptor. Acids are detected by the sour receptor. A particular amino acid, glutamate, tickles the umami receptor. Turns out there are twenty-ish different bitter receptors, good for detecting potential poisons, but they all send their signal to the same line that tells you “bitter”.
Smell, on the other hand, is complex. I learned that the olfactory bulb has a direct route to the brain that bypasses the brain stem, the gate for most other neuronal signals. Unlike the tongue with its one-to-one taste-to-channel setup, smell is multi-faceted. Johnson describes it this way: “The signal the brain gets from a taste molecule is like hitting one key on a piano: it activates its own distinct indicator that’s easy to tell from the the others. The signal that a smell molecule activates is more like a QR code: a two-dimensional pattern of many unique indicators… It’s impossible to pin down single smell elements in isolation… smells have multiple sensory qualities compounded together. The way we perceive them is more like seeing a face than tasting a taste… This is frustrating for simple categorization but, in its limitless variety, very fun and delicious for flavor.”
In chemistry, the organizing principle of the different elements is the Periodic Table. You can do something similar with flavors. That’s the Second Law. That’s where developing a vocabulary is useful: you could have broad categories such as fruity or floral or woody or vegetal. You could then drill down a little: something fruity could be citrusy. And that citrus could remind you of an orange, a lemon, or a grapefruit. For each of the five tastes, Johnson provides a set of elementary rules: what they are and what they are used for. I loved the chapter on salts: While I knew there were various types, I had mostly only cooked with simple table salt and soy sauce; but Johnson reminded me that you can get salty tastes from other salty ingredients: anchovies, cured meat, miso, and more. In the section on umami, Johnson explains how the signal sent by the receptor intensifies when both glutamate and inosine monophosphate (IMP) are both present. What else did I learn? Bitter flavors can be effectively chaperoned by the other four tastes. Spicy hot and menthol cold come from touch-receptors on our tongue. And that I like foods that release various sulfur molecules!
The Third Law on extracting and infusing flavor focused on techniques. It reminded me that I can draw on flavorful examples in my chemistry classes when I’m discussing solubility in water versus oil, distillation, diffusion, colligative properties, and intermolecular forces. And the Fourth Law is all about chemistry: using heat to transform raw food molecules into tasty and aromatic ones, or to coopt fermenting micro-organisms that specialize in creating alcohols, acids, and other assorted volatiles that give us rich and complex flavors. (I haven’t developed the vocabulary to describe these yet!) Reading these two sections made me think about how the chemistry I study in my research intersects with the joy of cooking. I investigate the interactions of aldehydes and amines; that’s the Maillard reaction of browning meat.
All this made me excited about potentially teaching a class on the Flavors of Chemistry. I can add this to the list of things that excite me, and whether I’ll actually get a chance to teach these as part of the standard curriculum in my department. One of the best motivators for me to learn more is to force myself to teach something new! And if anyone wants to delve into the subject, Flavorama is a great starter!
