Design and application of emulsion-filled hydrogels for functional foods.

Emulsion-filled hydrogels (EFHs) have emerged as transformative soft-matter systems that bridge the gap between lipid-based emulsions and polymeric hydrogels, enabling multifunctional applications in modern food design. Hydrogel networks act as a protective layer for emulsions by imparting tenable texture, enhanced stability, and responsiveness to environmental or physiological stimuli. This review provides a comprehensive overview of recent advances in the design, fabrication, and application of EFHs, emphasizing how formulation parameters and interfacial engineering govern their rheological, mechanical, and delivery performance. Key factors such as emulsifier type, filler concentration and size, matrix stiffness, lipid phase behaviour, and water-holding capacity are discussed in relation to viscoelasticity, texture, and stability. Special attention is given to the encapsulation and controlled release of bioactive compounds, including vitamins, antioxidants, and nutraceutical lipids, where EFHs improve bioavailability, oxidative resistance, and targeted gastrointestinal delivery. Beyond nutrient delivery, EFHs are increasingly explored as fat replacers, 3D-printable edible inks, and smart packaging materials, reflecting their multifunctionality in modern food systems. Despite these advances, large-scale implementation remains challenged by formulation complexity, oxidative stability, and regulatory acceptance. Collectively, EFHs represent a versatile platform that bridges materials science, food engineering, and nutrition, driving the development of next-generation functional foods with improved stability, targeted functionality, and sustainable consumer appeal.