Beyond Ultrasound Power: Acoustic Cavitation, Nucleation Kinetics and Polymorphic Control in Palm Oil Crystallization-A Critical Review

Ultrasound-assisted crystallization offers a route to manipulate the microstructure and functional properties of palm-based fats, yet acoustic, thermal, and hydrodynamic mechanisms are frequently conflated. This critical qualitative literature review synthesizes journal evidence published in 2020–2026 concerning acoustic cavitation, nucleation kinetics, polymorphic transitions, analytical characterization, and engineering translation. Direct palm-oil studies are differentiated from related work on cocoa butter, milk fat, coconut oil, and general sonocrystallization. The literature indicates that treatment position, subcooling, agitation, lipid composition, and emulsion architecture strongly moderate the observed response. Faster crystallization and smaller crystals do not necessarily predict higher hardness, greater solid fat content, or more stable emulsions. Nominal ultrasound power also provides an incomplete description of the actual acoustic field. A multiscale attribution framework is proposed that links acoustic forcing and energy dissipation to local temperature and flow, nucleation and growth, evolving polymorphs, crystal-network architecture, and application-specific performance. The review recommends thermal-history-matched controls, characterization of delivered acoustic energy, time-resolved scattering and NMR measurements, and transparent system-level energy balances. It concludes that ultrasound should be evaluated as a conditional, state-dependent processing tool rather than a universally beneficial crystallization intensifier.