Activation of bitter taste receptors by saponins and alkaloids identified in faba beans (Vicia faba L. minor).

Despite their interests, faba beans are characterised by bitterness but little is known about its compounds that activate the 25 human bitter receptors (TAS2Rs). This study aimed to determine the bitter molecules in faba beans, especially saponins and alkaloids. These molecules were quantified by UHPLC-HRMS in flour, starch and protein fractions of 3 faba bean cultivars. The fractions from the low-alkaloid cultivar and the protein fractions exhibited higher saponin content. Vicine and convicine were highly correlated with bitter perception. The bitterness of soyasaponin ßb and alkaloids was studied using a cellular approach. Soyasaponin ßb activated 11 TAS2Rs, including TAS2R42 whereas vicine activated only TAS2R16. The high vicine content should explain the faba bean bitterness considering that concentration of soyasaponin ßb was low. This research provides a better understanding of the bitter molecules in faba beans. Selection of low-alkaloid ingredients or alkaloid removal treatments could improve the faba bean flavour.

Origins of volatile compounds and identification of odour-active compounds in air-classified fractions of faba bean (Vicia faba L. minor).

Faba bean (Vicia faba L. minor) has many interests but is characterised by off-notes (negative odours/aromas) due to volatile compounds that are promoted during seed processing. Little is known about the volatile compounds of faba bean and their contribution to its odour. The purpose of this study was to determine the volatile compound origins of air-classified fractions (flour (F), starch (S) and protein (P)) from 3 faba bean cultivars and identify the odour-active compounds. Firstly, the volatile content of the fractions was extracted by solvent-assisted flavour evaporation (SAFE) and analysed by gas chromatography-mass spectrometry (GC-MS). A total of 147 volatile compounds were detected and categorised into 12 chemical classes. The P fractions had many volatile compounds from free fatty acid (FFA) oxidation and a higher lipoxygenase (LOX) activity. The volatile content suggested that cultivar 1 (C1) was confronted with a biotic stress at field whereas cultivar 2 (C2), richer in molecules from amino acid (AA) degradation, was contaminated by microorganisms in the field. Secondly, 35 odour-active compounds (OACs) were identified by GC-olfactometry (GC-O) and 12 odour-classes were used to describe the faba bean odours. The P fractions had higher detection frequency (DF) than the S and F fractions. P2 had a more complex odour profile due to important FFA and AA degradation. This work provides a better understanding of the impact of cultivar and processing steps on the faba bean volatile content. Selection of pulse-based ingredients with low volatile compounds could improve their flavour and increase their consumption.

Faba Bean (Vicia faba L. minor) Bitterness: An Untargeted Metabolomic Approach to Highlight the Impact of the Non-Volatile Fraction.

In the context of climate change, faba beans are an interesting alternative to animal proteins but are characterised by off-notes and bitterness that decrease consumer acceptability. However, research on pulse bitterness is often limited to soybeans and peas. This study aimed to highlight potential bitter non-volatile compounds in faba beans. First, the bitterness of flours and air-classified fractions (starch and protein) of three faba bean cultivars was evaluated by a trained panel. The fractions from the high-alkaloid cultivars and the protein fractions exhibited higher bitter intensity. Second, an untargeted metabolomic approach using ultra-high-performance liquid chromatography-diode array detector-tandem-high resolution mass spectrometry (UHPLC-DAD-HRMS) was correlated with the bitter perception of the fractions. Third, 42 tentatively identified non-volatile compounds were associated with faba bean bitterness by correlated sensory and metabolomic data. These compounds mainly belonged to different chemical classes such as alkaloids, amino acids, phenolic compounds, organic acids, and terpenoids. This research provided a better understanding of the molecules responsible for bitterness in faba beans and the impact of cultivar and air-classification on the bitter content. The bitter character of these highlighted compounds needs to be confirmed by sensory and/or cellular analyses to identify removal or masking strategies.

Heat Treatment, Cultivar and Formulation Modify the Sensory Properties and Consumer Acceptability of Gels Containing Faba Bean (Vicia faba L. minor) Protein Concentrates.

Faba bean (Vicia faba L. minor) is an emerging plant-based ingredient due to its environmental, nutritional and functional benefits. However, like other pulses, it exhibits many off-flavours that limit its consumption. Little is known about the flavour of faba beans, and previous studies have focused on volatile compounds and the overall flavour. In the present study, xanthan gum gels were formulated with crude or heated protein concentrates from three faba bean cultivars and with the addition of oil and/or salt. A trained panel analysed the sensory properties of these gels, and a consumer test was carried out to assess their acceptability. The gels formulated with crude protein concentrates exhibited bitterness and green, metallic and rancid notes that decreased consumer appreciation. The heat treatment promoted pleasant notes such as potato, cereal and haricot bean notes and attenuated the most penalising descriptors associated with off-flavours. Cultivar 2 was characterised by fewer off-flavours and should be preferred over the other cultivars for the formulation of faba bean products. This work provides information on the sensory properties of different cultivars of faba bean concentrates and information likely to help improve their acceptability in the context of the formulation of food intended for humans.

Characterization of a novel strain of Aspergillus aculeatinus: From rhamnogalacturonan type I pectin degradation to improvement of fruit juice filtration.

Aspergillus spp. are well-known producers of pectinases commonly used in the industry. Aspergillus aculeatinus is a recently identified species but poorly characterized. This study aimed at giving a comprehensive characterization of the enzymatic potential of the O822 strain to produce Rhamnogalacturonan type I (RGI)-degrading enzymes. Proteomic analysis identified cell wall degrading enzymes (cellulases, hemicellulases, and pectinases) that accounted for 92 % of total secreted proteins. Twelve out of fifty proteins were identified as RGI-degrading enzymes. NMR and enzymatic assays revealed high levels of arabinofuranosidase, arabinanase, galactanase, rhamnogalacturonan hydrolases and rhamnogalacturonan acetylesterase activities in aqueous extracts. Viscosity assays carried out with RGI-rich camelina mucilage confirmed the efficiency of enzymes secreted by O822 to hydrolyze RGI, by decreasing viscosity by 70 %. Apple juice trials carried out at laboratory and pilot scale showed an increase in filtration flow rate and yield, paving the way for an industrial use of enzymes derived from A. aculeatinus.