A good truffle, black or white, should be firm yet resilient to the touch, and should be very pungent—the white variety especially. If a truffle does not smell intensely, don't buy it—and never buy one that feels spongy when pressed with the finger, for that means it's old. Fresh black truffles have a black exterior with a slightly rough texture that suggests a dog's nose. Inside, they should be blackish-brown, with grayish-brown veins. White truffles are a pale yellowish-beige on the outside and brown with beige veins inside.