Dry fractionation of lentils: balancing protein enrichment, antinutritional factors, and techno-functional properties

This study investigated the impact of dry fractionation processes on the macronutrient composition, antinutritional factors (ANFs), and functional properties of lentil-based ingredients. Lentil seeds were processed through dehulling, extrusion, and air classification at two classifier speeds, obtaining fractions with several protein contents. Protein and starch contents were quantified, with major ANFs including phytic acid, saponins, α-galactosides, total phenolic compounds (including tannins), and trypsin inhibitors. Functional properties such as protein solubility (pH 3–9), water- and oil-holding capacities, emulsifying and foaming properties, and least gelation concentration were also assessed. Dehulling (mechanical seed coat removal) is a pre-treatment for the other two processes. It slightly modified macronutrient composition but drastically reduced seed coat-associated compounds, leading to a marked decrease in phenolic content (0.60 to 0.07%) and tannins (0.55% to 0.04%). Extrusion, a mechanical-thermal process conducted at 160°C, effectively reduced thermolabile components, decreasing saponins by 70% and trypsin inhibitors by 85%, with no impact on protein content (∼29%) and improved water-holding capacity and gelation properties. Air classification led to a strong protein enrichment, up to 59%, yielding a protein concentrate with enhanced solubility, emulsifying stability, and foaming properties. However, this enrichment was accompanied by concentrating protein-associated ANF, such as alpha-galactosides (3.8 to 7.5%), saponins, phytic acid, and trypsin inhibitors. Overall, the results highlight a technological trade-off between protein concentration and ANF content. While extrusion is effective for reducing ANFs and improving structuring properties, air classification yields highly functional protein-rich ingredients suitable for emulsified and foamed systems. These findings demonstrate that dry fractionation offers flexible and sustainable strategies to tailor lentil ingredients for specific food applications, providing a promising alternative to conventional wet extraction processes for the development of plant-based foods.