EMP's Daniel Humm Asks 'Where Is the Acid?' at Harvard

"I never finished high school," Eleven Madison Park’s Daniel Humm told a packed audience as he began his lecture last night. "In fact, I hated going to school." He ultimately left school at 14 to become a cook, a decision that was "not very popular" with his parents at the time but has opened "incredible doors" to "unbelievable" opportunities.

Fast forward to eight years ago. Humm arrived in the United States from his native Switzerland with a couple hundred dollars, a couple suitcases, mostly full of chef’s clothes, knives, and cookbooks; and no knowledge of English. "This is the American dream," he said last night (in fluent English), referring to having the opportunity to speak at Harvard and share his story.

Rachel Leah Blumenthal

At Eleven Madison Park, Humm and his team keep New York and its history in mind, finding the intersection between elegant fine dining and an artistry inspired by the farmers, fishers, and artisans from the New York region. The restaurant is housed in what was once meant to be the lobby of the tallest building in the world before the Great Depression got in the way, and Humm called it "such a New York space, such a New York room," explaining that it’s important to him that they pay homage to the place.

"Acid just makes food better."

After the introduction to the restaurant, Humm delved into the topic at hand: "Where is the acid?" The question, he noted, is one his staff hears from him "more than they probably care to remember." Acid, Humm explained, balances a dish. "It catches your attention. It kind of wakes you up. Acid just makes food better." Unlike a traditional French reliance on heavy fats like butter and cream, Humm uses acid to provide the primary flavors in his cuisine, keeping meals lighter and leaving guests wanting more. He traces his love of acidic flavors back to childhood, when he enjoyed tomatoes, roasted chicken with rosemary and lemon, and other similar dishes. Now, at Eleven Madison Park, Humm and his team have known for a few years that "acid is the foundation" of their cuisine. They’ve even begun making and barrel-aging their own vinegars in-house.

Acid can serve three main purposes in food, explained Humm: it adds flavor, it changes the structure of other ingredients, and it plays a role in preservation, both in pickling and in fermentation.

Going from Black and White to Color

First, consider flavor. Acids balance out other tastes; imagine, for example, a bitter espresso served with a sour slice of lemon — the acid tempers the bitterness. Taking it a step further, aroma is also part of the equation. Imagine a plain old lemon sorbet made with lemon juice. "That’s like every lemon sorbet that’s out there," Humm said. "It’s good, but…" Rub a sugar cube with lemon skin and then use that sugar to season the sorbet, and you’ve elevated the flavor of the sorbet by adding the aroma of the lemon in addition to the actual lemon juice. The same idea applies when you peel your own grapefruit and immediately eat it. The aromas have been released all over your hands, which enhances the experience — it’s much better than if you’re served pre-sliced grapefruit. Aroma comes into play in cocktails a lot, too, like that twist of orange in a Manhattan.

"It's like going from black and white to color."

When it comes to flavors and aromas from acids, the brain makes a connection between the two, and the experience is elevated. "It’s like going from black and white to color," said Humm. Acids are like stepping into Oz, apparently. He demonstrated the difference acid can make by presenting everyone with two bottles: a maple soda and a maple soda with apple cider vinegar. The former was pleasant enough but just plain sweet, while the latter had a balance between sweet and sour that most people enjoyed a lot more. While the difference isn’t always as extreme in food, "the right amount of acid can elevate a dish."

Maple soda samples. The one on the right also contains apple cider vinegar.

Acids are commonly used in packaged foods to improve flavor (and also improve shelf-life, conveniently). "They add acid to make shitty food taste better," said Humm, noting that he uses that knowledge in his own cuisine with the goal of making a "great product an unbelievable product."

Eggs Marinated in Vinegar Yield Creamier Yolks

Acid’s second use: changing the structure of other ingredients. Milk and acid yield curd, for example — the basic premise of cheese-making. Humm described one dish at the restaurant where milk, lemon juice, and hay (for added flavor) are heated together, which causes the milk to separate. After straining, you get curds and whey; the latter is discarded in most situations, but for this dish, it becomes part of a broth that is poured tableside over gnocchi made from the curds.

This property of acid is also what makes ceviche possible. Humm applies the same idea to a scallop dish where the scallops are marinated in a green apple juice and ascorbic acid. The scallops get a firmer texture, and the ascorbic acid (which has a relatively neutral flavor) also keeps the apple juice from turning brown.

After seven days, the yolks were barely liquid anymore.

Acid’s structure-changing magic also comes in handy with eggs. "I love eggs," said Humm. "Eggs are probably one of the most versatile things we work with." In order to make the creamy yolks creamier, the team tried marinating the yolks in white balsamic vinegar for two days, and sure enough, the yolks became thicker and creamier. After seven days, the yolks were barely liquid anymore.

Color change is also an indicator that acid is at work. Humm showed the results of an experiment with red cabbage, adding different acidic and basic ingredients to six different jars, which resulted in a colorful virtual pH meter, from white wine vinegar to bleach ("obviously you don’t want to eat this.") Along the same lines, color can be a helpful indicator that the blueberry muffin you’re about to eat won’t be so great. If you see a green ring around the blueberries, it means that there was too much baking soda in the batter; it’s reacting with the acid from the berries.

Red cabbage exposed to a variety of ingredients, from acidic to basic. From left: white wine vinegar, white wine, cabbage juice, baking soda, lye, and bleach.

Bad Bacteria Will Destroy the Cucumber...or It Will Destroy You!

But add some acid, and you've got a pickle.

Finally, acid plays a role in preservation, whether you’re interested in pickling or fermenting. For pickling, the addition of acid kills off the "bad" bacteria. (Imagine just leaving a cucumber out on its own for awhile. Bacteria will begin to grow, and "it will destroy the cucumber...or it will destroy you!" warned Humm, laughing.) But add some acid, and you’ve got a pickle.

Goodbye, bad bacteria.

In the fermentation process, acid is naturally produced. One fermented product at Eleven Madison Park is mustard greens, which are combined with salt, water, onions, and ginger.

Humm described a dish at the restaurant that makes use of both pickling and fermentation: foie gras with the fermented mustard greens, pickled sunchokes, and a relish made of onions and mustard seeds. The benefit of using acids for preservation is that you can make use of out-of-season ingredients; he serves this dish in the winter. The acid also acts to balance the richness of the foie gras.

Where Is the Acid?

So, back to the main question: Where is the acid? At Eleven Madison Park, basically everywhere. As Humm said at the beginning, it’s really the foundation of everything they do at the restaurant. The pantry is full of bottled vinegars (balsamic, sherry, red wine, and beyond), vinegar powders (malic acid, lactic acid, etc.), their own house-made vinegars, fresh citrus fruits, and sour dairy products that contain lactic acid, like yogurts.

Choosing still or sparkling "changes the experience of your meal dramatically."

Acid is also in an unexpected place: sparkling water. Carbon dioxide is a source of acid, so adding it to water brings the water from a near-neutral pH level to an acidic level. (At the restaurant, they measured it at 4.15, around the same acidity as tomato juice.) Seemingly the most simple question at the beginning of the meal, still or sparkling, suddenly takes on a new level of complexity. Choosing still or sparkling "changes the experience of your meal dramatically." (Humm generally prefers still.)

Since acidity is taken so seriously at Eleven Madison Park, a pH meter is just as important as a thermometer or a scale. But even when all of the numbers are perfect, even when the sauce that goes on a sweet and sour duck dish is consistently at a pH level of 4.6, the measurements aren’t everything. "We can use all the scientific tools," said Humm, "but it will never replace the palate or the talent of the chefs who are in the kitchen."

Rachel Leah Blumenthal

The Harvard Science & Cooking lecture series continues next Monday, November 17, with Jody Adams of Rialto in Cambridge, Massachusetts, speaking about fermentation. The event is free and open to the public; seats are first come, first served. More details can be found on the Harvard website.