Edible oleofilms with high vegetable oil content obtained from novel soy protein isolate/gelatin/chitosan nanofiber emulgels

Edible oleofilms (composite hydrocolloid-liquid oil films) containing high oil content can provide better functionality (e.g. water resistance) than just-hydrocolloid-based films. However, stabilization of these systems is very challenging, since the large amounts of liquid oil in the film matrix may lead to phase separation and oil-off. Herein we report the construction of oleofilms containing more than 66% soybean oil. To do this, new structured emulgels, based on soy protein isolate-gelatin-chitosan nanofiber (ChNF), were first prepared, and then oleofilms were made from emulgels by casting method. The influence of ChNF concentration (0–75% wt based on the total protein content) on the characteristics of the emulgels was also evaluated. Briefly, with the increase in ChNF level, the droplet size and polydispersity index of emulgel decreased (from 695.60 to 423.05 nm, and from 0.92 to 0.45, respectively, p < 0.05), and its centrifugation stability and gel strength increased (from 74.82 to 79.93%, and from 143.82 to 228.32 g, respectively, p < 0.05). Moreover, no oil-off was observed in emulgel samples. It was observed that oleofilm with the highest ChNF content (75% wt) had significantly lower water solubility (26.63%), water vapor permeability (7.99 g mm/m2 d1 kPa1), higher contact angle (80.36°), thermal stability (Tg = 51.8 °C; Tm = 139.2 °C), antibacterial activity (against E. coli and S. aureus) and comparable oxygen permeability (1.48 × 10−3 g/m2s) and tensile strength (42.04 MPa), as compared to the control (oil-free and non-reinforced) sample. Based on the results, the developed oleofilms have the potential for use in the preservation of moisture-sensitive foods.