Membrane processing and crystallization are common separation technologies that are widely used to recover, extract and purify food materials. A literature review is provided in this chapter, to highlight the role of ultrasound in mitigating fouling in membrane processing, as well as improving product quality, separation efficiency and repeatability in crystallization processes. Typical examples of ultrasound-assisted membrane processes include microfiltration and ultrafiltration of fruit juices, whey and milk. Sonocrystallization has been mainly studied for the formation of ice, salts, sugars, and lipids in food processing. To minimize energy consumption, ultrasound at low frequency with optimal intensity should be selected to avoid membrane damage and changes to physicochemical properties of food materials.