Preparation of bilayer nano-oleogel by whey protein isolate and soy lecithin for fish oil encapsulation and its application in cookies

In this study, a bilayer nano-oleogel system was designed and prepared by incorporating fish oil into varying levels of glyceryl monostearate (GMS), followed by encapsulation with soy lecithin and whey protein isolate (WPI). The formation of the nano-oleogel involved utilizing an oleogel/water nanoemulsion technique, which was followed by freeze-drying to remove water. The initial coating with lecithin yielded an average oleogel size of 144.8 nm, which increased to 561.5 nm after the second coating with WPI. Mechanical behavior analysis assessed the effect of varied GMS content on oleogel stability. The results of low-field nuclear magnetic resonance analysis exhibited a T2 relaxation time blueshift from 114.9 to 103.5 ms post fish oil encapsulation, implying reduced proton mobility in the nano-oleogel due to increased GMS within lecithin and WPI double layers. The results of differential scanning calorimetry analysis indicated enhanced thermal stability with higher GMS content in oleogels. Electronic nose analysis revealed that gelation and layer-by-layer encapsulation resulted in an off-flavor reduction from fish oil. Furthermore, the nano-oleogel was successfully used as a shortening substitution in making cookies with acceptable properties. Our findings suggested that the prepared nano-oleogel with flavor-inhibition capabilities could be used for replacing unhealthy solid fats.