Fermentation of dry- and wet-extruded pea protein texturates for flavor development

In the production of plant-based meat alternatives, texturized vegetable proteins (TVP) are a popular choice as base ingredients. However, these can have undesired off-flavors, which negatively affects consumer experience. Examples are distinctive green, and beany notes as well as a lack of desired meat flavor. This can be counteracted by using microbial fermentation as a processing step, with the potential to reduce off-flavors and create new odor-active compounds. Therefore, pea protein texturates produced via high-moisture (HMPT) and low-moisture (LMPT) extrusion cooking were fermented for 4 weeks at 15 °C, using Staphylococcus carnosus and Kluyveromyces marxianus in otherwise sterile microaerophile conditions. Microbial and metabolic activity were assessed, aroma profiles were determined by headspace solid-phase microextraction-gas chromatography-mass spectrometry-olfactometry (HS-SPME-GC-MS-O), key odor-active compounds were identified and relative peak areas of these compounds compared. High viable cell counts (cfu/g) were documented over the course of 4 weeks. Assessment of metabolic activity revealed increased tyrosine levels in LMPT compared to HMPT samples. Similarly, 53 (LMPT) and 41 (HMPT) perceivable odor-active compounds were identified prior to fermentation in the TVP samples. Of these, 17 compounds were identified as commonly known key off-odors in pea proteins which were significantly reduced throughout the fermentation. S. carnosus led to more characteristic final odor profiles, with desirable and undesirable flavors depending on the raw material. K. marxianus led to reduction beyond perceivability of several odor-active compounds, causing less intense odor profiles.