The production of whey protein concentrate powders is often limited by the fouling of the ultrafiltration membranes and the low heat stability of the whey protein solutions. Ultrasonic treatment of whey solutions has previously been shown to break down protein aggregates and improve heat stability. This study investigates the use of ultrasound as a pre-treatment step to improve downstream ultrafiltration performance. Results show that sonication alone alleviated membrane fouling to a small extent. However, the use of ultrasound following heat exposure reduced membrane pore blockage and growth of the foulant cake greatly, relative to heat exposure in the absence of ultrasound. The extent of changes to pore blockage and cake growth was greater at higher solids concentration. In all cases, the protein concentration in the permeate remained unchanged. This work has the potential to reduce energy requirements in the ultrafiltration of whey as feed pre-treatment by both ultrasound and the combination of heat and ultrasound produced a lower viscosity feed solution. (C) 2013 Elsevier B.V. All rights reserved.