The highest quality truffles that make their way to market are harvested with the help of trained truffle dogs, who can identify ripe truffles by scent. These dogs are also trained to leave unripe truffles to mature undisturbed in the ground. Unfortunately, some truffles are still harvested by raking, which indiscriminately produces mostly immature, unripe truffles. A truffle that is harvested before it reaches maturity will never properly ripen for culinary use.