Lactic fermentation to improve the aroma of protein extracts of sweet lupin (Lupinus angustifolius)

Lupin protein extracts (LPE) are prone to the emission of a beany off-flavour during storage, which confines its application in foods. Fermentation of LPE using several lactic acid bacteria was conducted to reduce off-flavour formation in stored samples. The aroma profile of untreated LPE was compared to those of fermented protein extracts (LPEF). Hexanal and n-hexanol were used as indicator substances of progressing lipid oxidation. The most powerful odourants were evaluated by GC-olfactometry-flavour dilution analysis and identified according to their mass spectra, odour descriptions, and retention indices. Twenty two volatile substances with dilution factors equal to or higher than 100 were determined in both LPE and LPEF, amongst them n-pentanal, n-hexanal, 1-pyrroline, dimethyl trisulfide, 1-octen-3-one, 3-octen-2-one, 1-octen-3-ol, and β-damascenone. The aroma profile was significantly modified by the fermentation process and the off-flavours were reduced and/or masked by newly formed compounds.