Browsing by Author "Oja-Lipasti, Roosa"

Due to the high protein content in legumes, legume protein concentrates and isolates are becoming popular and are currently used in food as a substitute for animal-based proteins. Unfortunately, the sensory quality of legumes can be compromised by a beany flavour, bitter taste, and an astringent mouthfeel. The objective of this study was to investigate the bitterness of two faba bean concentrates, one that was untreated and another deflavored to reduce the negative sensory attributes. The presence of bitter tasting compounds in the water-soluble extract of the concentrates was determined using chemical and sensory evaluation. The first hypothesis of the study was that the deflavored concentrate, its water-soluble and water-insoluble fraction are less bitter than the untreated concentrate and its fractions. The second hypothesis was that the water-soluble fraction of the concentrates is more bitter, due to bitter water-soluble phytochemicals. The faba bean protein concentrates were extracted in water and the phytochemical profiles of the water-soluble extracts analysed by UHPLC-MS. The phytochemical profiles of the water extracts were compared and the compounds that differed in their intensity identified based on the mass/charge ratios (m/z) of [M-H]- ions and fragment ions. The bitterness and total flavor intensity of the water suspensions of the concentrates, the supernatants and insoluble residues were investigated by sensory evaluation using a trained panel. The study showed that the aqueous suspensions of both supernatants were as bitter as their concentrates, therefore the compounds causing the bitterness were easily soluble in water. The untreated concentrate suspension and its supernatant were more bitter than the deflavored concentrate suspension and supernatant, suggesting that different amounts of specific compounds in the samples may explain the difference in bitterness. In the UPLC-MS analysis, the intensity of the 12 compounds was higher in the aqueous extract of the untreated concentrate compared to the deflavored aqueous extract. For example, hydroxy fatty acids, some of which have been shown to cause bitterness, were present in the water extracts of the untreated concentrate. The bitter compounds in the concentrate had been reduced or their formation prevented by the deflavoring treatment. Differences in the enzymatic activity of lipase and lipoxygenase enzymes was lower in the deflavored than untreated samples suggesting that an enzyme inactivation treatment may have been used in the production of the deflavored concentrate. Nonetheless, despite the treatment, the deflavored concentrate was still bitter which necessitated more research to identify the bitter compounds and also studies on how to effectively reduce the off-flavour in legume-based protein concentrates.