The clamor you heard was brought about by the stream of power through the wires. This power was made by the response of the tomato mash and metal. The zinc responds with the corrosive in the tomato, and minor particles with a negative charge (electrons) are set free into the tomato juice. These negative electrons are pulled toward the copper cathode, which has a positive charge. (In power, similarly as in attraction, opposites are inclined toward one another). Each battery has a negative side and a positive side. In the tomato battery, the copper anode is the positive terminal, and the zinc cathode is the negative terminal. The electric flow keeps running from negative to positive, and back around again when associated in a total circuit.