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. James Beard loved McDonald's fries. 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.

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