A Screw Blancher that is substantially sealed during operation to increase food product heating speed and efficiency. The blancher has a sealed housing, a novel substantially sealed food product inlet, and a novel substantially sealed food product outlet. A heat transfer medium, such as water or only steam, is introduced into the blancher to heat the food product inside the blancher. During operation, food products are substantially continuously introduced into the blancher through the food product inlet, processed by the blancher, and thereafter discharged from the blancher through the food product outlet. As a result, a greater amount of food products can be more quickly heated to a desired temperature using a blancher of this invention as compared to a blancher that is not sealed.