PROC-014: Stability of Tocopherols and Tocotrienols during High-moisture Extrusion of Plant-based Protein Ingredients

There is an increasing demand for plant-based protein ingredients and products made from them due to environmental and nutritional reasons. High-moisture extrusion (HME) is a processing technique that can be used to produce meat alternatives. The ingredients are rich in many bioactive compounds, e.g., tocopherols and tocotrienols (tocols), but it is poorly known how stable they are during processing. Thus, the aim was to study stability of tocols in plant-based protein ingredients during HME. Ingredients included faba bean flour (FBF), protein concentrate (FBPC) and isolate (FBPI), pea protein isolate (PPI), lupine flour (LF), protein concentrate (LPC) and isolate (LPI), and oat fiber concentrate (OFC). Ingredients or mixtures were subjected to HME using a twin-screw extruder equipped with a long cooling die. The effects of the long cooling die temperature (LCDT) and screw speeds were tested. Tocols were extracted from the ingredients and the extrudates by accelerated solvent extraction using ethanol as the solvent and analyzed by normal-phase performance liquid chromatography with fluorescence detection. There was a large variation in tocol contents in the ingredients: LPC had the highest content (171 µg/g dm) and LPI the lowest one (4 µg/g dm). In general, tocol levels were lower in most extrudates compared to their ingredient mixtures. Extrusion of FBPC decreased tocol levels by 1731%, while due to extrusion of FBPC, FBF and FBPI mixtures the levels decreased more (4050%) as also of LPC, LF and LPI mixtures (ca 43%). However, in PPI:OFC(50:50) mixtures no changes in tocol contents occurred during HME at LCDT of 40 and 80 °C, and screw speeds of 300 and 500 rpm, whereas in mixtures of FBPC and FBPI tocol levels were lowered by 1030% during HME at LCDT of 40 and 80 °C. Processing plant-based protein ingredients using HME is expected to cause some losses of tocols, but the effect is likely dependent on the chemical composition of ingredients and perhaps also on the processing parameters of HME.