Co-Inoculation of <i>Latilactobacillus sakei</i> with <i>Pichia kluyveri</i> or <i>Saccharomyces boulardii</i> Improves Flavour Compound Profiles of Salt-Free Fermented Wheat Gluten

A wheat gluten fermentation process with the inoculation of different microorganisms under salt-free conditions has the potential to produce varying flavour profiles. As research on the co-fermentation of yeasts and lactic acid bacteria (LAB) in salt-free wheat gluten fermentation is scarce, the current work studied the flavour impact on fermented wheat gluten by the co-inoculation of <i>Latilactobacillus sakei</i> with one yeast (<i>Saccharomyces boulardii</i> or <i>Pichia kluyveri</i>). The results showed that similar glucose and organic acid levels were detected, but early death of yeasts was observed during liquid-state fermentation (LSF) in co-fermentations. The concentrations of most free amino acids were comparable. Volatile compound analysis showed synergistic effects in co-cultured fermentations on the production of certain compounds such as isoamyl acetate. Principal component analysis revealed clear differences in volatile profiles between co-fermentation and single-strain fermentation. Therefore, a fermented sauce produced by co-inoculating LAB and yeast with a new and fruitier flavour was developed.