Plant-based burgers: effects of protein source, type of extrusion and cooking technology on oxidation status and in vitro digestibility

The effects of cooking method (microwaving/pan frying) and in vitro digestion of plant-based burgers formulated with different protein types (soy/pea) and extrusion types (low/high moisture) were assessed. A conventional beef burger was used as control. Every formulation was adjusted to 18.1–19.5 % of protein. Plant-based burgers showed lower cooking losses (4–13 %) than beef burgers (26–30 %), with microwaving resulting in the highest losses across all samples. Plant-based burgers formulated with high moisture extrusion showed the lowest protein digestibility (66.8–73.2 %). No effect of the cooking method was observed in lipid and protein digestibility in any sample. Soluble peptides increased during in vitro digestion in all samples, with beef burgers showing the lowest levels. The amount of malondialdehyde increased whereas carbonyls decreased in the bioaccessible fraction in all samples during in vitro digestion. Burgers formulated with low moisture extrusion showed the highest lipid oxidation, both after cooking and after in vitro digestion. DPPH values decreased (17–59 %) and ABTS increased (277–810 %) during in vitro digestion. These results suggest that the protein digestibility and lipid oxidation of plant-based burgers (before and after digestion), are more strongly influenced by the type of extrusion than by the type of protein or cooking method applied.