Scientific inquiry about what we eat, how we prepare it, and with what method is nothing new. Not since Galen (129 -216 CE) interpreted the theories of Hippocrates has so much science been applied to our food.
Seemingly simple, Galen’s Theory of Four Humours, was the original food combining diet to achieve balance and health. Much mischief has been gotten up to since the first century, but Galen’s theories lingered into the 19th century and some terms are still in use today. That the neologism “neutraceutical” is enjoying some currency; food as medicine, is an homage to the Greek physician-philosopher.
Although not much has radically changed in the tools we use in food preparation since the Bronze Age many a commonplace is older than we think. Invented in the 17th century by the French physicist and inventor Denis Papin’s “steam digester” remains, with little modification, today’s modern pressure cooker.
The how and why of basic (and not so basic) methods of food preparation have long enjoyed scientific scrutiny. Chemists have been interested in meat stock preparation and, more generally, food preparation since the 18th century; none more so than Antoine-Laurent de Lavoisier. In 1783, he studied the processes of stock preparation by measuring density to evaluate quality. In reporting the results of his experiments, Lavoisier wrote,
Whenever one considers the most familiar objects, the simplest things, it’s impossible not to be surprised to see how our ideas are vague and uncertain, and how, as a consequence, it is important to fix them by experiments and facts.
It was, after all, the age of scientific inquiry.
Another important figure was Benjamin Thomson (1753-1814), later knighted Count Rumford, who studied culinary transformations and made many proposals and inventions to improve them. His experiments with heat brought about the invention of the drip and the percolator coffee pot, and his slow cooking of a mutton shoulder presages the current sous-vide method. His name lives on with a trademarked baking powder, which he did not invent.
Justus von Liebig, the father of organic chemistry can not be overlooked. Many are the great educator’s contribution to the field, including his, Researches on the Chemistry of Food (1847). Today, with some irony, he is memorialized in the boullion cube, the highly concentrated extract of beef today sold under the Oxo trademark..
In 1912, Parisian scientist Louis Camille Maillard (1878-1936) undertook studies of the reaction between amino acids and sugars. He was trying to figure out how amino acids linked up to form proteins. He discovered that when he heated sugars and amino acids together, the mixture slowly turned brown. This work is today considered his major contribution and the Maillard reaction (“enzymatic browning”) was named after him.
Fast forward to the late 1980s. Prof Emeritus of Physics at Oxford and bon vivant, Nicholas Kurti felt dismayed and defeated by a soufflé.
I think it is a sad reflection on our civilization,” he wrote, “that while we can and do measure the temperature in the atmosphere of Venus we do not know what goes on inside our soufflés.
He set out to find and define “precisions” in cooking — not just traditions and passed down accepted rules and wisdom. Like the scientifically curious before him, empirical truth was his goal. When he teamed up with the French Chemist, also an enthusiastic bon vivant, a new discipline was hatched Molecular and Physical Gastronomy… or molecular gastronomy.
What follows, in two parts, are explanations of everyday kitchen ingredients, techniques and tools. As it turns out, while it is important to know the how of cooking, it is just as important to know the why.
1. What is an emulsion?
The old saying “you can’t mix oil and water” is disproven by the existence of the emulsion. The most common emulsions we make are mayonnaise and Hollandaise sauce, both made by simply bonding together oils in the presence of water — one cold, one hot. Basically, an emulsion (sauce) is one in which you take two liquids which have been dispersed one into the other in tiny globules that cling to each other, stay suspended, and don’t settle out.
A basic mayonnaise incorporates three elements: oil, egg yolk, and lemon juice or vinegar. Slowly beating oil into the egg yolk (which is 50% water) and lemon juice (more water), the oil breaks down into tiny droplets that become suspended in the yolk and lemon juice due to the emulsifying agent lecithin in the egg yolk. This phosphorus containing molecule has long “tails” that are lipophilic (fat loving) and hydrophilic (water loving) heads. The tails burrow into the oil and the positive and negatively charged heads attract the water. These, as you might surmise, are the go-between that attracts and firmly binds the water and oil to form the creamy, much loved sauce.
Mayonnaise can suspend approximately eight times the oil in relation to the water content. At the molecular level it is the tiny oil droplets that are enshrouded in a thin sheen of water that has taken place.
The same kitchen magic occurs in Hollandaise sauce, a so-called “Mother sauce,” with the addition of a gentle heat and switching out butter for oil.
2. What makes a soufflé rise?
Author of, An Everlasting Meal, Tamar Adler recently mused,
There’s much to ponder in a soufflé’s rise without involving science. The gastronomic pleasure we take in risen foods — yeasted bread, a buttery biscuit, a high-risen soufflé — seems to derive less from the half that’s there than from the half that isn’t, from the airy absence that makes presence more keenly felt.
She discovered the magic was in the egg, more exactly the egg whites, and even more exactly the proteins. Rich in proteins, egg whites are able to hold small pockets of air that, when beaten, magically turns into foam.
Egg whites are a pure protein called conalbumin. Proteins denature when exposed to heat, acid, or air. When air is vigorously incorporated into egg whites, the proteins denature – they unfold – and become stuck to neighboring proteins forming sheets. Stuck-together proteins are rigid enough to stabilize small air pockets that expand and create the foam that will provide the scaffolding for the soufflé when gently folded into the soufflé. Egg white should be beaten to the soft peak stage not further.
To this foam is often added a flavored béchamel sauce if savory, and if sweet, milk (often in a pastry “cream”) sugar, fruit, a liqueur. Gently “fold” the egg whites into the base in three batches, using a rubber spatula — do not stir. Put in the prepared baking dish, soufflé mold or ramekins and then into the oven.
As any gas warms it expands. In the soufflé there are millions of tiny air bubbles and as they heat up they expand. The heat also cooks the egg proteins, moving moisture that adds steam to the air pockets causing them to expand even more. Pushed to the limits of its container, the soufflé can only rise out of its dish.
A soufflé will always be more voluminous in the oven than on the table. As soon as it is removed from the oven the temperature begins to drop and the air pockets contract, causing a little shrinkage. The cooked egg white proteins will hold their shape briefly allowing the soufflé to arrive puffy and tasty.
Here are some hints for a successful soufflé.
- Use a balloon whisk to whip your egg whites.
- Egg whites beaten in a copper bowl become copper – conalbumin and will withstand a greater intensity of heat and will tend to rise higher.
- It is critical that not even a speck of egg yolk mars the whites. If there is any yolk, any fat at all, in the egg white, it will not whip up.
- Egg whites are easier to whip up at room temperature, so let your separated eggs sit out while you prepare the rest of your ingredients.
- Old egg whites whip up more easily than fresh eggs.
- A soufflé needs a straight-sided dish or mold to rise.
- If you grease and dust with crumbs or sugar (depending) the rising whites will have a convenient “ladder” to assists their climb.
- A greased collar of parchment paper tied around the dish, extending above the top of the dish may be needed for high-rising soufflés.
- You can make the soufflé up to the point of baking it and then refrigerate it for a few hours (not more than three).
3. Caramelize — What is it?
Louis Camille Maillard was a French Chemist who characterized the initial steps in the ’searing’ process — that intricate series of chemical reactions that gives rise to the tasty browned bits — as being the relationship of a so called reducing sugar (such as fructose, lactose, maltose and glucose) with protein.
The initial “Maillard reaction,” as it became known, takes place between a certain part of the sugar molecule (its carbonyl group) and a certain part of the protein molecule (an amino group in one of its amino acids). After the first step, the Maillard process continues through a series of consecutive and simultaneous chemical reactions resulting in dark colored polymers most of which are pleasantly aromatic and flavorful.
Bread, cookies, cakes, meats, poultry, fish, beer, chocolate, popcorn, and coffee all owe a flavor debt to heat and the Maillard reaction. During the process, hundreds of distinct flavor compounds are created. These, in turn, break down to form yet more new flavor compounds, and so on. Each type of food has a very distinctive set of flavor compounds that are formed during the Maillard reaction. The importance of this “explanation,” call it a discovery, should be self-evident. It also made a world of possibilities available to the profession of flavor (and artificial) flavor makers.
4. How do you get Corn Syrup from Corn?
Corn has been around since at least 4,000 BCE…corn syrup, since 1886…high fructose corn syrup, 1967. There is insufficient cane and beet sugar produced in the US to satisfy the sweet cravings of our population. So sugar is imported.
We could and do, however, help with the nation’s sugar craving by tapping into some of the enormous corn crop produced annually in the US. Corn syrup is made from cornstarch. Disregarding corn’s water content, each kernel is 84% carbohydrates, each containing bio-chemicals mostly sugars, starches and cellulose. By a process that involves soaking, grinding, centrifuges, and mills, the starch is stripped from the fiber. Keep in mind that starches and sugars are closely related; each starch molecule is a matrix of smaller molecules of the sugar, glucose. Corn starch is converted into ordinary corn syrup through a process called acid hydrolysis, in which heat and hydrochloric acid breaks down the starch molecules and coverts them to sugar at this point cornstarch has become corn syrup.
The sweetness in cane, beet, or maple sugar comes from sucrose. Corn syrup derives from glucose and is only about 60 percent as sweet as the other three sweeteners. To close the sweetness gap manufacturers add an enzyme that converts some of the glucose to fructose that can be manufactured in levels of 42 -90% fructose content. High fructose corn syrup (HFCS) in soft drinks, ice cream is about 55% fructose.
5. What is the Dutch process that makes cocoa cocoa?
The history of chocolate is long and fascinating. From the Aztec ritual drinking of xocotlatl (theobroma, food of the gods), to the European adoption of drinking chocolate in 17th century, to the world-changing event provided by Thomas Fry in 1847 who made the first eating chocolate, the subject has filled volumes. Prior to Fry’s tablet was the contribution by Coenraad Johannes van Houten who, in addition to inventing a press for making solid chocolate, also developed the process of alkalization (called Dutching) that made cocoa water soluble. By treating cocoa powder with alkaline salt (potassium or sodium bicarbonate) the color and taste of the cocoa is modified, being darker and milder than “natural” cocoa and having a neutral pH factor seven or eight. Unprocessed cocoa nibs have a pH of about five and a half.
Different levels of acid in a recipe affect the leavening agent, the different pH level in regular or Dutch cocoa can radically affect whether or not a baked item will rise. Therefore, Dutch process cocoa powder cannot be used in recipes that incorporate baking soda as a leaving agent as there is no acid to activate the baking soda. It can, however be used with baking powder as a leavening agent.
Some studies maintain that “Dutching” diminishes beneficial antioxidants inherent in cocoa before processing. •
Lead image courtesy of James Vaughn via Flickr.