When they break out the broccoli rape in the kitchen at Della Notte in Little Italy, they don't put up a "Bitter - Handle With Care" sign, but they might.
Caution is recommended with such things as broccoli rape and arugula and fenugreek and a range of stuff falling into a "bitter family" of foods and beverages. It's probably safe to consider this an acquired taste - the sting on the tongue, the metallic slick that seems to linger on the roof of the mouth long after other tastes fade.
"I find people either like it or they don't," says Della Notte executive chef John Rybock, referring to broccoli rape or rabe or rapini, a green and leafy relative of the cabbage and turnip known for its bite. He uses it often enough at the restaurant, in a fried pork dish and in salads, for instance. One has to be careful.
"It's a hard item to pair with a lot of stuff," says Rybock. "It's right out there, it's right up front. It's the main flavor. It's hard to quiet it down."
All the more so for an audience in the United States rather than Italy, where the palate seems more accustomed to bitter tastes. Consider the common Italian use of rape and arugula, not to mention espresso, strong licorice and sundry alcoholic concoctions of herbs, roots and flowers with a more or less bitter taste.
Many of these liqueurs are also called digestivos, as they're said to help digestion and are supposedly best taken after a meal. The same claim is made about the bitters used as cocktail flavorings.
Bitter foods have inspired any number of health claims, some more grounded in research than others. It's no coincidence that foods that to some palates taste like medicine happen also to have medicinal properties.
The bitterness and the benefits arise from many of the same chemical compounds called "phytonutrients," phenols, flavonoids, terpenes, among others. Research affirms an implied contradiction:
"When it comes to phytonutrients, the demands of good taste and good health may be wholly incompatible," says an article published four years ago in the American Journal of Clinical Nutrition. The article says that many of the same compounds that taste bitter, acrid or astringent also appear to protect against cancer and cardiovascular disease.
"All medicines are toxins," says Paul Breslin, an associate professor at the Monell Chemical Senses Center in Philadelphia. "Toxins at low levels can be good for you."
As these substances are also off-putting to the taste buds, researchers and food producers have for years tried various ways to resolve the conflict between bitterness and benefits. The food industry has tried breeding out some of these chemical compounds, but that tends to also diminish the health value of eating vegetables.
Scientists have identified the human chromosome that influences the ability to discern bitter taste, but so far that discovery has not led to developments in the food world.
Chocolate has its bitter components, as does coffee, but most of the bitter family resides in the produce department. Endive or chicory, dandelion, escarole, frisee, collards, radicchio, watercress and, of course, rape and arugula, all fall under the heading of "bitter greens," although not all are green. Less well-known is bitter melon, also known as Balsam pear or bitter gourd, used most commonly in Asian cooking.
All these make their strongest impression on the back of the tongue, where most bitter taste receptors are found, although Breslin says bitter tastes can be sensed all over the mouth. Humans and other mammals are capable of discerning a wide range of substances as bitter, although they all may taste about the same. The evolutionary logic says the more bitter compounds can be detected, the better the protection against eating poisons, many of which taste bitter.
Likewise, plants evidently produce bitter compounds as a defense against being eaten.
For the chef, the question is different, if not less complex: What works with bitter?
At Della Notte, Rybock says arugula - usually more mild than rape - works in various salad combinations, including one involving balsamic vinegar, green apples, red onions and fried pork chop. Another dish combines arugula and scallops in a ravioli filling, setting the mild sweetness of the scallop against the bitter arugula.
At Sotto Sopra, chef Maurizio Ghidinelli uses arugula in an octopus salad with tomato, red onion, capers and boiled potato.
"Arugula is a little spicy flavor, and bitter is good with the sweet flavor of the tomato and the acidity of the tomato," says Ghidinelli.
Ghidinelli uses broccoli rape in pasta dish at Sotto Sopra, specifically orecchiette, rape, anchovies, capers, fresh tomato and a bit of tomato sauce.
Then there's the house Sotto Sopra pizza, a thin crust with mozzarella cheese and prosciutto, piled generously with fresh arugula. With a fresh mesclun salad, it makes a nutritious meal.
Sometimes the trick to a healthful dish is getting the toxins just right.