Fibre–emulsifier interactions shape the lipid digestion behaviour of high internal phase emulsions

High internal phase emulsions (HIPEs) are highly viscous emulsions with broad applications in structured foods and lipophilic nutrient delivery. This study explores how natural fibres (asparagus and citrus) affect lipid digestion in HIPEs stabilized by whey protein isolate (WPI) or Tween 20, using an in vitro model. The results indicate fibre addition did not alter the intestinal viscosity and played no direct role in lipolysis. The type of emulsifier (whey protein isolate (WPI) or Tween 20) and the type of fibre influence intestinal lipolysis by modulating the gastrointestinal stability of emulsions. WPI-stabilized HIPEs were unstable under gastric conditions (without gastric lipase), which could be modulated through the addition of fibres, particularly citrus fibre, which enhanced gastric stability. In WPI-stabilized HIPEs, citrus fibre improved gastric stability and maintained interfacial area, doubling the initial lipolysis rate and increasing final lipid digestibility (to ∼1.3 times). In contrast, Tween 20-stabilized HIPEs became unstable in the intestinal phase, with citrus fibre addition reducing (to ∼0.6 times) lipid digestibility. This is confirmed by a model study analysing lipolysis and coalescence rate constants. It emphasizes the critical role of emulsion stability throughout the GI tract and demonstrate how different fibre–emulsifier combinations modulate coalescence and lipolysis rates during digestion. The results provide valuable insights for the design of fibre-enriched HIPE systems with tailored digestive properties. • Dietary fibres impact in vitro lipolysis kinetics through emulsion stability. • Citrus fibre enhanced the gastrointestinal stability of WPI-stabilized HIPEs. • Fibre addition reduced the intestinal stability of Tween 20-stabilized HIPEs. • Initial droplet size and stability determine the rate and extent of lipolysis.