Ultrasound-Responsive Liquid–Liquid Microgels for Targeted Delivery of Bioactive Polysaccharides and Antioxidants in Multi-Stage Thermal Processed Functional Foods

Thermally processed functional beverages require carrier systems capable of protecting and selectively releasing labile bioactives under industrial multi-step heating regimes while responding to mild, food-safe triggers. In this study, ultrasound-responsive liquid–liquid microgels (US-LLMGs) were engineered via controlled liquid–liquid phase separation (LLPS) between whey protein isolate (WPI) and a polysaccharide matrix composed of β-glucan and sodium alginate, subsequently stabilized with enzymatically oxidized (+)-catechin to form a dense, protein–polyphenol hybrid shell. The formulation parameters (pH, ionic strength, polyphenol concentration) were optimized using a central composite design to maximize encapsulation efficiency (EE), shell integrity, and acoustic responsiveness. The optimal microgels (pH ۶.۴, ۱۵ mM NaCl, ۰.۲۲% w/v polyphenol) exhibited a hydrodynamic diameter of ۲.۵۵ ± ۰.۰۸ µm, polydispersity index ۰.۱۸ ± ۰.۰۲, ζ-potential −۱۹.۲ ± ۰.۶ mV, and β-glucan EE of ۹۳.۴ ± ۰.۹%. Following three sequential heat treatments (HTST pasteurization, warm homogenization, final ۹۰ °C/۲ min holding), EE retention remained at ۹۲.۱ ± ۱.۰%, with antioxidant activity (ORAC, DPPH) preserved above ۹۵%. Low-intensity ultrasound at ۸۰ kHz/۰.۹ W·cm⁻² triggered a rapid release of ۴۸.۷ ± ۲.۲% within ۵ min and ۸۲.۶ ± ۲.۱% within ۱۵ min (p < ۰.۰۰۱ vs. control). Kinetic modelling revealed a predominantly anomalous transport mechanism (n = ۰.۶۳ ± ۰.۰۲, Korsmeyer–Peppas) driven by US-induced shell permeability enhancement via acoustic microstreaming. The integration of LLPS-derived microgel morphology, polyphenol-mediated shell compaction, and frequency-specific acoustic sensitivity yielded a platform combining exceptional thermal resilience with on-demand, site-specific release performance. These findings position US-LLMGs as a scalable, industrially compatible delivery vehicle for hydrophilic bioactives in next-generation functional beverages, enabling post-processing activation without compromising sensory or physicochemical stability.

کلیدواژه ها:

Ultrasound-responsive microgels ، Liquid–liquid phase separation ، Controlled release ، Polysaccharide delivery ، Phenolic antioxidants ، Multi-stage thermal processing