Development and characterization of lentil protein foam-templated oleogels as potential plant-based fat mimetics

Growing demand in the food industry for sustainable alternatives to animal products has led to a need for plant-based fat mimetics that effectively simulate the experience of consuming animal fats and can replace commonly used highly saturated tropical oils.  Lentils are an affordable, protein-rich pulse crop, but there is currently limited information on the functionality of lentil protein for plant-based food applications.  In this study, lentil protein fractions (concentrate, isolate, and soluble fraction) were isolated using a solvent-free extraction method. Foaming behavior of each fraction was characterized both without and with a stabilizing hydrocolloid (xanthan gum), and optimized foaming conditions were used to prepare freeze-dried foam templates to absorb and structure canola oil.  Microstructure of the foam templates was dependent on protein composition, with the globulin-rich isolate fraction displaying a more uniform, less compact structure and the concentrate fraction yielding a denser, more irregular protein network.  The soluble protein fraction was unable to form stable foam templates at any pH condition.  The oleogels prepared with lentil isolate had slightly higher oil sorption and oil binding capacities (~98 wt% and ~85 wt% oil content, respectively) compared to concentrate (~92 wt% and ~72 wt% oil, respectively).  Lentil isolate oleogels displayed lower cohesiveness, springiness, and gumminess than concentrate oleogels by texture analysis, likely due to the less dense, more brittle structure of their foam templates.  Both lentil isolate and concentrate oleogels maintained elastic-dominated viscoelastic behavior with no melting-like behavior when heated up to 100°C.  Isolate oleogels displayed a notable thermal transition around 55°C (by DSC), and both fractions experienced thermally-induced stiffening in the rheological response after heating.  This work provides a baseline for the performance of lentil protein-polysaccharide systems for structuring vegetable oil-based fat analogs, which could support the design of more sustainable, healthy plant-based food products.