Simultaneous vehiculation of curcumin and riboflavin in bigels produced through WPI cold-set gelation

Abstract

The influence of curcumin (model hydrophobic compound) and riboflavin (model hydrophilic compound) on the structure and physicochemical properties of bigels produced with cold-set whey protein isolates (WPI) was assessed. The hydrogel phase was produced with WPI (11% w/v) while for the oleogel phase, sunflower oil and glycerol monostearate (GM) (10% w/v) were used. Curcumin (0.03 mg/mL) was added to the oil phase and riboflavin (0.5 mg/mL) to the water phase. Bigels were produced by hot emulsification (18.000 min−1, 2 min, 55 °C) of different hydrogel:oleogel ratios (90:10, 50:50 and 10:90). NaCl (200 mM) was added to the aqueous phase prior the emulsification. Bigels were evaluated through microscopy, XRD, FTIR, viscoelastic, texture, release kinetics and in vitro digestion analyses. XRD and FTIR showed that the addition of compounds led to some possible structural differences. Microscopy images showed an increase of the oil droplets size proportionally to the amount of oil present, and a conversion of the structure from oil in water (O/W) to water in oil (W/O). The structural differences led to different mechanical behavior. For the bigels with the isolated compounds an improvement in the gel network was observed, making it more structured, according to the phase that is being added. Regarding controlled release, higher values for the 90:10 formulation were observed for both compounds due to the matrix erosion. For bioaccessibility, curcumin presented similar values for 90:10 and 10:90 bigels, and riboflavin showed a growing bioaccessibility, with lower values for bigel 90:10.