Supercritical fluid extrusion of pea flour and pea protein concentrate: Effects on off-flavor removal and sensory improvement

This study was intended to provide a novel process that fills a knowledge gap in relation to the enhancement of pulses utilization. The primary goal was to develop an experimental framework for using a high-pressure supercritical fluid extruder (SCFX) as a continuous bioreactor to produce off-flavor reduced and functionally superior pulse flours and protein concentrates in a single step. The current study focused on using SCFX processing to remove off-flavor from pulse flour and protein concentrates, enhancing the quality, acceptability, and marketability of pulse-based products. Supercritical carbon dioxide (SC-CO₂), a well-known green solvent, was employed in combination with an extrusion system to achieve off-flavor reduction at larger scale. Using various methods such as headspace solid-phase microextraction-gas chromatography mass-spectroscopy (HS-SPME-GC-MS) and sensory evaluation, this study demonstrated that SCFX significantly reduced the off-flavor in pea flour (PF) and pea protein concentrate (PPC). HS-SPME-GC-MS analyses identified major off-flavor compounds in unextruded PF and PPC, including 1-hexanol, 1-octanol, 1-nonanol, nonanal, and 2-alkyl methoxypyrazines. Following SCFX treatment, all these compounds except nonanal were removed. Total off-flavor compound concentration dropped from 923 to 126.5 ng/g in PF, and from 571.7 to 65.9 ng/g in pea protein concentrate PPC after SCFX treatment. Sensory evaluation corroborated these HS-SPME-GC-MS findings, showing that over 80% of the participants could accurately distinguish the extruded samples from the unextruded ones, perceiving the treated samples as having the least beany flavor. These findings highlight the efficacy of SCFX processing in enhancing the sensory profile of pulse-based products by removing off-flavor compounds.