Nevertheless, the change had a profound effect on the nation's agriculture and diet. A familiar food had been transformed into a highly processed industrial commodity. McDonald's fries now come from huge manufacturing plants that can peel, slice, cook, and freeze two million pounds of potatoes a day.

The rapid expansion of McDonald's and the popularity of its low-cost, mass-produced fries changed the way Americans eat.

In 1960 Americans consumed an average of about eighty-one pounds of fresh potatoes and four pounds of frozen french fries.

In 2000 they consumed an average of about fifty pounds of fresh potatoes and thirty pounds of frozen fries.

Today McDonald's is the largest buyer of potatoes in the United States.

The taste of McDonald's french fries played a crucial role in the chain's success -- fries are much more profitable than hamburgers -- and was long praised by customers, competitors, and even food critics.

Their distinctive taste does not stem from the kind of potatoes that McDonald's buys, the technology that processes them, or the restaurant equipment that fries them: other chains use Russet Burbanks, buy their french fries from the same large processing companies, and have similar fryers in their restaurant kitchens.

The taste of a french fry is largely determined by the cooking oil.

For decades McDonald's cooked its french fries in a mixture of about seven percent cottonseed oil and 93 percent beef tallow. The mixture gave the fries their unique flavor -- and more saturated beef fat per ounce than a McDonald's hamburger.

In 1990, amid a barrage of criticism over the amount of cholesterol in its fries, McDonald's switched to pure vegetable oil. This presented the company with a challenge: how to make fries that subtly taste like beef without cooking them in beef tallow. A look at the ingredients in McDonald's french fries suggests how the problem was solved.

Toward the end of the list is a seemingly innocuous yet oddly mysterious phrase: "natural flavor." That ingredient helps to explain not only why the fries taste so good but also why most fast food -- indeed, most of the food Americans eat today -- tastes the way it does.

Open your refrigerator, your freezer, your kitchen cupboards, and look at the labels on your food. You'll find "natural flavor" or "artificial flavor" in just about every list of ingredients. The similarities between these two broad categories are far more significant than the differences. Both are man-made additives that give most processed food most of its taste.

People usually buy a food item the first time because of its packaging or appearance. Taste usually determines whether they buy it again.

About 90 percent of the money that Americans now spend on food goes to buy processed food.

The canning, freezing, and dehydrating techniques used in processing destroy most of food's flavor -- and so a vast industry has arisen in the United States to make processed food palatable.

The flavor industry is highly secretive. Its leading companies will not divulge the precise formulas of flavor compounds or the identities of clients. The secrecy is deemed essential for protecting the reputations of beloved brands.

The fast-food chains, understandably, would like the public to believe that the flavors of the food they sell somehow originate in their restaurant kitchens, not in distant factories run by other firms. A McDonald's french fry is one of countless foods whose flavor is just a component in a complex manufacturing process. The look and the taste of what we eat now are frequently deceiving -- by design.

A person's food preferences, like his or her personality, are formed during the first few years of life, through a process of socialization. Babies innately prefer sweet tastes and reject bitter ones; toddlers can learn to enjoy hot and spicy food, bland health food, or fast food, depending on what the people around them eat.

The human sense of smell is still not fully understood. It is greatly affected by psychological factors and expectations. The mind focuses intently on some of the aromas that surround us and filters out the overwhelming majority.

People can grow accustomed to bad smells or good smells; they stop noticing what once seemed overpowering. Aroma and memory are somehow inextricably linked. A smell can suddenly evoke a long-forgotten moment.

The flavors of childhood foods seem to leave an indelible mark, and adults often return to them, without always knowing why. These "comfort foods" become a source of pleasure and reassurance -- a fact that fast-food chains use to their advantage. Childhood memories of Happy Meals, which come with french fries, can translate into frequent adult visits to McDonald's.

On average, Americans now eat about four servings of french fries every week.

The Atlantic Monthly; January 2001; Why McDonald's Fries Taste So Good - 01.01; Volume 287, No. 1; page 50-56