The invention provides a food processing method for inhibiting the growth of microorganisms in food and the acquired food thereof; the method comprises mixing the pyrroloquinoline quinine active substances with the food. The addition of the pyrroloquinoline quinine active substances can inhibit the growing of microorganisms in food, thus achieving the purpose of prolonging the preservation period of the food. The invention further provides the function of the pyrroloquinoline quinine active substances in food processing, as well as the preparation and the purification method thereof. The preparation method of the invention can efficiently prepare high purified pyrroloquinoline quinine.