Taste: Surprising Stories and Science About Why Food Tastes Good (43 page)

Conversely, if you were to tinker with your acidic waters until they all tasted exactly as sour as one another, their pH measurements would be likely to fall within a fairly wide range of about a whole pH point. Believe it or not, at the same pH level, vinegar water tastes more sour than hydrochloric acid water. Of course, this would be a very low concentration of acid, because hydrochloric acid at a higher concentration can corrode metal and burn human skin.

At the other end of the pH scale lives alkalinity. Alkalinity is actually an indication of a substance’s ability to buffer an acid or decrease acidity (or increase the pH). Here’s an everyday food example that will help explain how this works.

When you brew a cup of thick, rich, black coffee, the two Basic Tastes will be an assertive bitterness and a slight acidity. You can balance the sourness with cream.

That’s because black coffee falls within the acidic range of the pH scale, with a measurement around 5.0. Milk, half-and-half, and cream have a pH that’s higher, between 6.0 to 8.0. If you add 7.0 milk to more acidic 5.0 coffee, your resulting beverage will have a pH higher than 5.0, probably closer to 6.0. In other words, you move your creamy coffee up the pH scale—and this means it tastes less acidic. Milk buffers coffee. Of course, other things are going on. When you add milk that contains fat or cream or half-and-half, you’re also changing the mouthfeel, which helps to tame some of the alkaloid compounds that make coffee bitter.

The change in pH from a slightly acidic 5.0 to a less acidic 6.0 might seem small, but moving coffee up the pH scale by one point means that it’s ten times less acidic. So adding cream to coffee results in a creamy beverage with ten times less sourness.

A lot of the foods you probably love are acidic and this can make heartburn a chronic illness for some. The physical problem is that your throat tissues weren’t built for the 1.0 gastric acidity that bubbles up into your chest. To remedy this, you can take antacid tablets, which are alkaline and buffer the acid up to a higher pH, making it less likely to burn and cause discomfort.

At low levels, acids taste sour to us. At high levels, they also have a tactile component: an irritaste. The trigeminal nerve that carries sensations of pain and touch can detect odorless acids when you sniff them. If you’ve ever gotten a deep noseful of vinegar, you may have experienced this yourself. I like to reduce balsamic vinegar into a sweet-and-sour syrup to drizzle on strawberries, ice cream, and grilled proteins such as salmon or pork. But if I heat it up too quickly and the volatiles start to waft off, I can feel it in my nasal passages. Even if I couldn’t smell it, I could detect it.

In the Mattson food lab, we have a complicated relationship with the sour Basic Taste.

We rely on a high level of acidity to keep microbes away from and out of our foods. For example, the acidic kick of canned salsa and tomato and marinara sauces allows food companies to market them without refrigeration.

FDA’s Classification of Foods Up to pH 8.0

Source:
http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/ucm122561.htm

Sourness lends a brightness that picks up the flavor of food, which is highly desirable in many dishes. Yet sourness can be difficult to mask. Sometimes you don’t want it around, except to make our food safe from nasty bugs like E. coli and salmonella.

The problem is that not all flavors work well with sourness. Take chocolate, coffee, or creamy things like milk. To make chocolate milk that can be sold without refrigeration, it would be necessary to add acid to it—that would make it taste weirdly sour, which is never good. People don’t generally buy things that taste weird. Instead of adding acid, we go to great lengths—and expense—to sterilize shelf-stable chocolate milk (or soy milk or rice milk) in an aseptic clean-room or a harsh canning process. We don’t have to do that to naturally tart tomato sauce or orange juice.

Winemakers and jam and preserve makers balance Brix (sweetness) and acid (sourness). Condiments, which are almost always high in acid, are also balanced with salt (think mustard and hot sauce) and sometimes sweet (think ketchup and Thai sweet chili sauce). Juices are high in acid but balanced by sweetness. Bartenders, sometimes known as
mixologists
these days, are also excellent practitioners of balancing sour with other Basic Tastes. They use the bitterness of alcohol as a third counterpoint to sweet and sour. Take the most popular cocktail in America: the margarita. Without the bitterness of the tequila, the drink would be cloyingly sweet and disconcertingly sour.

Some acids taste salty. And some salts taste sour. Often we confuse them. Scientists have proved we tend to misperceive salt as sour and sour as salt because of the way they’re detected at the taste receptor level.

When Roger and I went to the Center for Smell and Taste in Florida, we were tested for how well the taste buds on certain areas of our tongues worked. Researchers “painted” a cotton swab dipped into a sour solution across different parts of our tongues. In some places, it tasted sour. In others, it tasted salty. This is because the sour and salt Basic Tastes are both perceived the same way: through a channel. Sweet, bitter, and umami are perceived in a key-in-lock fashion: the molecule clicks into the receptor.

Perhaps because of their similar detection mechanism, sourness can enhance saltiness and vice versa. Delfina’s Craig Stoll uses acid to drive the intensity of his food.

“You’ve got salt and acid that you keep amping up in a vinaigrette until it hits this crescendo of flavor. Where we want it,” he says, “if you had to sum up our food, it would be depth and brightness,” by which he means acidity. “Most
of our stuff is balanced with some acidity somewhere. And some of it’s hidden. We finish a lot of our sauces with vinaigrette. We do a leg of lamb where we’ll make a lamb jus and reduce it and on the pickup, we’ll warm it up and we’ll add a quarter or half ounce of sherry wine vinaigrette.” Stoll does the same thing with roast chicken and silken olive oil mashed potatoes. But he cautions that if you can taste the vinegar, his chef has added too much. He’s not using it for its flavor, but for its taste—the Basic Taste sour, which sparks food alive. Acidity is an easy way to literally make food more mouthwatering. Within a small, sour window, that is.