Ask any Vietnamese what his or her favorite sandwich is and he or she will most likely tell you that it’s the “banh mi,” which simply means “bread” in Vietnamese. The “banh mi” sandwich is a culinary pride of the Vietnamese, one that is similar in fame to the Philadelphians’ Philly Cheesesteak. The “banh mi” is a type of French baguette made from a mixture of rice flour and wheat flour. Hence, unlike its French cousin, the Viet baguette is often much lighter and crispier. With a spread of the luscious fatty pâté, made from a mixture of cooked liver, cognac, and buttery mayonnaise, when put together with several succulent slices of roast pork (and the oozing meat juice, of course), the “banh mi” sandwich finds the perfect harmony in taste with pickled shredded daikons and carrots and a touch of heat from the jalapeño pepper. At the basic level, these are all the ingredients needed to make a mouth-watering and delightful “banh mi,” arguably one of the best sandwiches ever known to humanity (but maybe I am a little bias). However, scientifically speaking, have you ever wondered what makes the taste of the “banh mi” sandwich so delectable, when beautifully prepared and made by a skillful artisan? Let’s explore the wonderful world of taste using the “banh mi” sandwich as the medium.
Before we delve into the complex world of taste, think mindfully about this question: What is taste? Most of us, if not all, learn in school that taste is the process of chemical receptors locating on the countless taste buds that line over the papillae (the bumps on your tongue), perceiving food molecules, and sending signals to the brain. The result is the perception of the five basic tastes: bitter, salt, sour, sweet and umami (savory). But is that all there is? Might it be possible that taste doesn’t have a textbook definition? What if the notion of taste is much more complicated than you think? In truth, taste is as much a psychological product as it is a chemical or physiological product; taste is the perceived result of a combination of signals from aroma, sight, sound (yes, sound), flavor and touch sensation associated with a food.
A longtime friend of mine, who proclaimed himself a “connoisseur in gastronomy,” once asked me: “What do you think accounts for the deliciousness in the “banh mi” baguette?”
I said, “It’s the crust, no?”
He then replied, “Not really. It’s the smell, I tell you. It’s the smell!”
He emphasized that the smell, or aroma, is what makes the “banh mi” so delicious. But ever since I understood the complexity of taste, I also knew that he was only half correct, as there are other scientific reasons as to why “banh mi” smells and tastes good. Let’s examine how we perceive taste chemically by looking at the main ingredient of the “banh mi” sandwich: the baguette.
What better experience is there to enjoy going to a bakery than to smell its freshly baked bread, or baguettes? Probably none (perhaps you can agree with me). The chemical reactions behind baking are probably ones that you already know: caramelization and the Maillard reactions. Caramelization and the Maillard reactions are similar because they are both non-enzymatic browning reactions that produce many compounds that impact the flavor of food. However, unlike the Maillard reactions, caramelization is the browning of sugar that does not involve amino acids. Some of the most famous dishes that also utilize the caramelization reaction like baked bread are Soupe à l’oignon à la Parisienne (aka French onion soup) and Confiture de lait (similar to dulce de leche). The major volatile compound that gives bread (or other dishes) its characteristic caramel and buttery note, 2,3-butanedione (or diacetyl), is released during caramelization. Therefore, diacetyl contributes to the richness of the aroma of the bread. However, diacetyl is but a small contributor. Most volatile chemicals, such as 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine, both of which contribute to the roasted and cracker-like aroma of bread, are released during the Maillard reactions. These chemicals are detected by the scent receptors in your nasal cavity when you eat or sniff food. Hence, the combination of chemical signals transmitted from your taste buds and nasal receptors to your brain then create taste (or flavor) that transcends the five basic tastes.
The usefulness of chemistry, i.e., the Maillard reactions, in understanding the taste of the “banh mi” sandwich does not stop there. The richness of the succulent roast pork is also created by the Maillard reactions. (Let’s give a tribute to the French chemist Louis-Camille Maillard, who we can thank for our deep understanding of the culinary arts). The Maillard reactions can be summarized in three steps: amino acids and sugars react to produce glycosylamine; glycosylamine isomerizes to produce ketosamine; ketosamine reacts in many ways to create even more products. One of the products, melanoidin, is said to contribute to the brown coloring of cooked foods, such as the roast pork in the “banh mi” sandwich. Many other end products of the Maillard reactions, such as alkylpyridines, furanones, and thiophenes, contribute to the nutty, meaty, burnt, mildly bitter and caramel taste of roast pork (and other dishes).
But these chemical and physiological reasons can only explain the composition of a delicious “banh mi” sandwich; they don’t explain why the roast pork tastes good, or why we like the crispy crust and aroma of the Viet baguette. Think about it this way: Do you actively think that you like baked bread because you are smelling diacetyl? Or do you also think that you like roast pork because you are tasting alkylpyridines or furanones for the nutty, meaty and burnt flavor? Unless you are an “OCD” chemist, the most likely answer is no. Instead, we turn to the psychological reason for why certain foods are so appetizing. Ivan Pavlov’s classical conditioning experiment with dogs explains how we are conditioned to like or hate certain things. The experiment portrays the concept of associative learning, which is the act of learning by linking certain stimuli, behaviors or events together in the process of conditioning. Therefore, associative learning explains we like certain foods, such as the “banh mi” sandwich.
Certainly, taste preferences take time to form, beginning from when we were toddlers still learning how to walk. We take in environmental cues and learn the sight, sound, and touch sensations associated with the food. I am half Vietnamese and I grew up eating lots of “banh mi” sandwiches for breakfast. I associate the food with my heritage, my family and my culture as those are the environmental cues that contribute to my taste preferences. But the crunchy sound of a crushed baguette, or the sight of the vivid colors of pickles in the “banh mi,” or even the soft but crispy texture of the “banh mi” crust all influenced my taste preference and conditioned me to like the sandwich. The impact was greater than that of my self-proclaimed connoisseur friend, who likes “banh mi” as much as I do. But he never experienced the taste of the sandwich the way I did simply because he didn’t grow up with it.
Ever since I came to Miami to attend the University of Miami, I have been experiencing an insatiable hunger for the “banh mi” sandwich. I drive for miles around South Miami on weekends in a quest for the best “banh mi” sandwich shop, but to no avail, as I cannot find one that is decent enough to even rival a mediocre “banh mi” sandwich in San Diego. I even tried to make my own, but I couldn’t find a bakery that sells the Viet baguette, or a store that sells pâté for the sandwich. Hence, my quest continues. I would love to share the taste that I experienced with everyone. Boy, if only I could find the rich and creamy French pâté in Miami to spread onto a crispy Viet baguette, with my homemade pickles tucked in with the oozing juice from several slices of roast pork, garnished with chopped cilantro. Mm, delicious.
I dedicate this article to Professor Otis (Ms. MO) and Professor Wafer for their tremendous help in improving me to become a better writer.