Improvement of the Aroma of Pea (Pisum sativum) Protein Extracts by Lactic Acid Fermentation

The formation of a green or beany off-flavor during storage of legume protein extracts limits their application in foods. Pea protein extracts were submitted to lactic acid fermentations to improve the flavor by either reducing off-flavor formation or by masking undesirable green notes. The aroma profiles of untreated pea protein extract (PPE) and fermented pea protein extract (PPEF) were compared to each other and to a commercial whey protein as a benchmark. Kinetic measurements of n-hexanal and n-hexanol formation were used as an indicator for progressing lipid oxidation and storage stability. The nonfermented and fermented pea protein extracts showed a shelf-life comparable to the commercial whey protein reference. Volatiles were identified and quantified using dynamic headspace sampling with subsequent coupled TDS-GC-MS and TDS-GC-olfactometry flavor dilution analysis. A total of 18 odorants with dilution factors equal to or higher than 100 were determined in PPE and 17 in PPEF. Altogether, 23 highly odor-active compounds were identified according to their mass spectra, odor impressions, linear retention indices, and standard substances in PPE and PPEF, among them n-hexanal, 1-pyrroline, dimethyl trisulfide, 1-octen-3-one, 2,5-dimethyl pyrazine, 3-octen-2-one, beta-damascenone, and guaiacol. The fermentation considerably amended the aroma profile of pea protein preparations resulting in a reduction or a masking of undesirable flavors.