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Volatile Compounds in Pulses
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This entry is adapted from the peer-reviewed paper 10.3390/foods10123140

The worldwide demand for pulse-based products is increasing in the face of climate change, but their acceptability is limited due to the presence of off-flavours. Off-notes contribute to negative perceptions of pulses (beany notes). Volatile compounds belong to a large variety of chemical classes. They are mainly produced from the oxidation of unsaturated free fatty acids and the degradation of amino acids during seed development, storage, and transformation (dehulling, milling, and starch or protein production).

pulses volatile compounds off-flavour odour-active compounds

1. Introduction

Pulses (Fabaceae) are an interesting alternative to animal proteins. They are rich in proteins, unsaturated fatty acids, and bioactive compounds and thus present nutritional and environmental benefits [1][2][3][4][5]. Moreover, they offer functional properties for food applications [2][3]. Many forms are available, such as whole seed, flour, starch, and protein concentrate/isolate [3]. Despite all of the interest in pulses, the presence of off-flavours is in some cases a barrier to their consumption by humans and limits their expansion [4][5][6].
Off-flavours or unpleasant flavours are related to negative organoleptic perceptions. They originate from different volatile molecules responsible for off-notes (unpleasant odours) and from sapid compounds [6]. These tasting compounds activate bitter taste receptors (TAS2Rs) located on the tongue and in the oral cavity. Astringent molecules can precipitate salivary proteins and lead to a loss of lubrification in the mouth [7]. Some saponins, phenolic compounds, alkaloids, peptides, and free amino acids contribute to pulse bitterness whereas phenolic compounds also seem to be involved in astringent sensations [6].
Many volatile compounds have been identified in pulses, and they are mostly responsible for unpleasant odours [6]. These compounds mainly originate from free fatty acids present in the grains and are oxidized into smaller molecules. This phenomenon naturally occurs in the grains but is intensified under stress conditions (water stress or mechanical or herbivore/insect attacks). The production of these compounds contributes to a defence mechanism for these plants and can continue after harvesting [8]. Small compounds, such as aromatic hydrocarbons, aldehydes, alkanes, alkenes, alcohols, ketones, acids, esters, pyrazines, terpenes, furans, and lactones, have been identified in pulses [6]. Even though each of these molecules has a specific odour, the perception of an aroma is often due to a mixture of different notes from several molecules [9]. Off-notes in pulses are described as beany, green, pea-like, earthy, hay-like, fatty, pungent, and metallic [6].

2. Origins of Volatile Compounds in Pulses

2.1. Oxidation of Unsaturated Free Fatty Acids

Different classes of volatiles, such as aromatic hydrocarbons, aldehydes, alcohols, alkanes, ketones (furans) and esters, are mostly derived from enzymatic or nonenzymatic oxidation (autoxidation) of free fatty acids. Although pulses have a low fat content (0.8–7% of seed weight), this mechanism is dominant and strongly contributes to unpleasant odours, such as herbal, green, pea, beany, mould, and rancid notes [10]. The synthesis of these compounds follows three phases.

2.2. Degradation of Free Amino Acids

The degradation of amino acids has been shown to be the second source of volatile compound production in pulses. Several origins exist, such as biodegradation in seeds, degradation by microorganisms, and Maillard reactions.

2.3. Degradation of Carotenoids

Terpenes can be derived from the degradation of carotenoids. Carotenoids are oxidized by LOX 2 at neutral pH and produce these volatile compounds [11]. This origin is highly disputed. Indeed, due to the low concentrations found in plants, these molecules would be absorbed by plant roots at the soil level during their cultivation and then accumulate in the seeds [12].

3. Extraction, Separation, Identification, and Semi-Quantification Methods

The characteristics of the studied pulses (cultivar and year and location of cultivation), conditions of storage, transformation, and volatile compound analysis are described in Table 1 [13][14][15][16][17][18][19][20]. Different classical methods are used to extract volatile compounds, which are briefly described here. By using HS-SPME (HeadSpace Solid-Phase MicroExtraction), the volatile compounds in the vapour phase are first adsorbed on a fibre and desorbed in the GC (Gas Chromatography) injector to be separated and identified. This method is robust, rapid, simple to use, and solvent-free but allows only semi-quantification due to competition between analytes on the fibre [21][22][23]. SAFE (Solvent-Assisted Flavour Evaporation) combines vacuum distillation and solvent extraction [24]. This method allows quantification by a standard but requires a long extraction time and requires the use of organic solvents to extract volatiles [23]. The differences highlighted in these two methods could also explain some differences between pulse volatile compounds.
Table 1. Characteristics of pulses: extraction and identification methods of volatile compounds.
Table
Code Pulses Cultivar Year Location Storage Seed Transformation Extraction Separation and
Identification		 References
Black bean Black bean (Phaseolus vulgaris L.) AC Harblack 2005 Morden, Canada Dry room (23 °C,
15–20% RH) (whole).		 Ground in flour (coffee mill) (whole). HS-SPME: 10 g in a 125-mL Erlenmeyer flask capped, DVB/CAR/PDMS Stable Flex SPME fibre at 50 °C for 1 h. GC-MS: desorption at 250 °C for 2 min, Supelcowax 10 polar column, started at 40/1/70 °C, then 70/5/200 °C and 200/50/250 °C. [25]
CDC Rio
Onyx
Pinto bean Pinto bean (Phaseolus vulgaris L.) AC Pintoba
Maverick
Dark red kidney bean Dark red kidney bean (Phaseolus vulgaris L.) ROG 802
Redhawk
Whole pea Pea
(Pisum
sativum L.)		 Eclipse (Yellow field pea) 2005 Near
Saskatoon, Canada		 4 °C (whole). Ground in flour (whole). HS-SPME: 3 g, CAR/PDMS SPME Fibre at 50 °C for 30 min. GC-MS: desorption at 300 °C for 3 min, VF-5MS capillary column, started at 35/6/80 °C and 80/20/280 °C. [26]
2006
2007
Dehulled pea - Before 2013 - In a glass bottle,
−18 °C.		 Ground in flour (dehulled). SAFE: 20 g in 100 mL of water, 2 h at 30 °C and 10–2 mbar. Liquid-liquid separation with 3 × 10 mL of CH2Cl2. Concentration using Kuderna Danish apparatus, 70 °C. GC-MS: ZB1.MS non-polar column, injection of 2 µL, started at 50/4/160 °C, then 160/15/320 °C. [27]
Pea protein Protein isolate, Nutralys® (dehulled, wet process).
- Before 2020 - - Protein concentrate (dehulled, dry process). HS-SPME: 1.5 g was dissolved into saturated NaCl solution for 1 h at 20 °C, then transferred into a bottle and incubated at 50 °C in an ultrasonic bath, insertion of the DVB/CAR/PDMS Stable Flex SPME fibre at 50 °C for 20 min. GC-MS: desorption at 250 °C for 3 min, DB-5MS column, started at 40/5/70 °C, then 70/10/200 °C and 200/50/250 °C. [28]
Chickpea Chickpea
(Cicer
arietinum)		 Kabuli
(Benying-1)		 2018 Urumqi, China −18 °C for a maximum of 3 weeks (whole).
−20 °C for a maximum of 1 week (powder).		 Dried using sunlight before storage (whole).
Ground to a fine powder (80 mesh, mill).		 HS-SPME: 1.5 g was dispersed in water and 5 mL was placed in a 20-mL headspace sampling vial and capped, PDMS/DVB fibre at 60 °C for 60 min. GC-MS: desorption at 250 °C for 5 min, PEG 20 M column, started at 35/5/130 °C and 130/9/200 °C. [29]
Desi
(YZ-364)
Faba bean Tannin Faba bean
(Vicia faba
L. minor)		 High tannin 2016 Alberta,
Canada		 In freezer bags (polypropylene), 22 °C and 18% RH in a dark and solvent-free room (flour). Ground in flour (impact mill) (whole). HS-SPME: 2 g was pre-incubated at 50 °C for 5 min, DVB/CAR/PDMS Stable Flex SPME fibre at 50 °C for 1 h. GC-MS: desorption at 250 °C for 60 s, DB-17 mod polarity column, 40/5/200 °C. [30]
Low tannin
Faba bean Location Low tannin
(13 cultivars)		 2009 Barrhead, Canada - Ground in flour (coffee mill) (whole). HS-SPME: 10 g in a 125-mL Erlenmeyer flask capped, DVB/CAR/PDMS Stable Flex SPME fibre at 50 °C for 1 h. GC-MS: desorption at 250 °C for 2 min, Supelcowax 10 polar column, started at 40/1/70 °C, then 70/5/200 °C and 200/50/250 °C. [31]
Namao,
Canada
Faba bean Storage High tannin 2016 Alberta,
Canada		 No storage. Ground in flour (micro-mill) with a water-cooled system to protect from overheating (whole). HS-SPME: 2 g was pre-incubated at 50 °C for 5 min, DVB/CAR/PDMS Stable Flex SPME fibre at 50 °C for 1 h. GC-MS: desorption at 250 °C for 60 s, DB-17 mod polarity column, 40/5/200 °C. [32]
In bags (PE), in a dark and solvent-free room, 60 days (flour). 22 °C, 19% RH.
4 °C,
9% RH.
−21 °C.
RH, relative humidity; SAFE, Solvent-Assisted Flavour Evaporation; HS-SPME, HeadSpace Solid-Phase MicroExtraction; PE, polyethylene.

4. Identification and Quantification of Volatile Compounds in Pulses

In Table 2, Table 3, Table 4, Table 5, Table 6 Table 7, Table 8, Table 9, Table 10, Table 11, Table 12 and Table 13, each table describes a chemical class of volatile compounds: aromatic hydrocarbons, aldehydes, alkanes/alkenes, alcohols, ketones, acids, esters (without lactones), pyrazines, terpenes, furans, lactones, and other volatile compounds. For each pulse, one column corresponds to the minimum and the maximum (min–max) of a set of different cultivars, harvest years, locations and conditions of storage, or seed transformations (dehulling and production of protein concentrates or isolates) (see Table 2 for more details).
Table 2. Aromatic hydrocarbons in pulses (expressed as percentages).
Table
Aromatic Hydrocarbons CAS Origin (s) Black Bean Pinto Bean Dark Red
Kidney Bean		 Pea Chickpea Faba Bean
Whole Dehulled Tannin Location Storage
Toluene 108-88-3 FFA 1,2 0.00–0.86 0.96–1.86 0.00–0.73 1.20–2.40 Coelution   0.26–0.37 0.88–0.96 0.41–3.12
m-Ethyltoluene 620-14-4               0.09–0.11   0.00–0.28
Benzene 71-43-2 FFA 4       0.00–0.50     0.09–0.11    
Ethylbenzene 100-41-4 FFA 1,2 0.00–0.45 0.00–0.44   0.30–0.80     0.12–0.17 1.19–1.28 0.19–0.73
1,2,3-Trimethylbenzene 526-73-8 FFA 2 0.00–0.54 0.54–1.03         0.12–0.13   0.00–0.21
1,3,5-Trimethylbenzene 108-67-8 FFA 2 0.00–0.77 0.81–1.84             0.00–0.19
Propylbenzene 103-65-1   0.00–0.35 0.00–0.40             0.00–0.19
Cumene 98-82-8 FFA 2 0.70–1.13 0.84–0.86 1.11–1.69 0.30–0.60       0.42–0.46  
p-Xylene 106-42-3 FFA 1 1.15–1.50 0.00–1.20 0.00–1.17 0.40–1.00       0.27–0.38 0.00–0.70
o-Xylene 95-47-6 FFA 1,2,4 0.95–1.16 1.14–1.73 1.13–1.45   Coelution        
m-Xylene 108-38-3 FFA 1         1.25        
4-Ethyl-m-xylene 874-41-9               0.05–0.07   0.00–0.64
p-Cymene 99-87-6           Trace   0.32–0.33    
Styrene 100-42-5 FFA 1,2,3; N 2,3 32.55–45.47 30.88–31.76 38.75–47.57 0.70–2.20   0.00–0.60   11.36–13.79 0.00–1.90
α-Methylstyrene 98-83-9   0.00–0.43 0.00–0.38 0.00–0.49            
Total     38.51–49.28 38.24–38.51 43.41–50.72 3.50–6.70 1.25 0.00–0.60 1.07–1.27 14.15–16.89 0.68–7.75
1 [26]; 2 [25]; 3 [31]; 4 [33][34]. FFA, free fatty acids; N, naturally present (not considered as a contaminant). The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], and “Dehulled” corresponds to dehulled pea flour [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], “Location” corresponds to different low-tannin cultivars that were harvested at 2 different locations in Canada [31], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) for 60 days and a control (sample stored for 0 days) [32]. No aromatic hydrocarbon was detected in pea proteins (concentrate and isolate) (see Table 1 for more details).
Table 3. Aldehydes in pulses (expressed as percentages).
Table
Aldehydes CAS Origin (s) Black
Bean		 Pinto
Bean		 Dark Red
Kidney Bean		 Pea Chickpea Faba Bean
Whole Dehulled Proteins Tannin Location Storage
Benzaldehyde 100-52-7 FFA 2; AA 5,7,11 2.36–3.64 2.58–2.60 3.46–4.04     0.00–2.11 0.00–2.19 0.36–0.45 2.09–2.10 0.46–0.85
4-Ethylbenzaldehyde 53951-50-1             0.00–0.54        
Phenylacetaldehyde 122-78-1 AA 3,5,7,11           0.00–0.67   0.14–0.17   0.21–0.39
Vanillin 121-33-5           0.16 0.00–0.08        
2-Methylpropanal 78-84-2 AA 11               0.49–0.51    
3-Methylthiopropanal 3268-49-3 AA 3,11           0.00–0.03        
2-Methylbutanal 96-17-3 AA 5,8,11           0.03–0.49   0.31–0.48   0.00–0.13
3-Methylbutanal 590-86-3 AA 5,7,11       0.00–1.00   0.00–0.10   1.04–1.17   0.36–0.59
Pentanal 110-62-3 FFA 2,9,10 0.00–0.59 0.60–0.79 1.03–1.11     0.00–0.73     0.96–1.21  
Furfural 98-01-1             0.00–0.05        
Hexanal 66-25-1 FFA 1,2,3,4,6,7,8,9,10 12.76–16.71 9.77–11.27 15.88–18.6 1.50–6.10 0.93 27.22–54.12   10.28–13.85 40.78–40.88 1.29–25.07
2-Ethylhexanal 123-05-7                     0.00–0.16
(E)-2-Hexenal 6728-26-3 FFA 1,2,4,8,9,10 0.00–1.60 0.00–1.67 0.00–1.75     0.00–0.19        
Heptanal 111-71-7 FFA 2,3,7,8,9,10 0.00–0.75 0.00–0.82 0.00–0.95     1.13–5.31   1.04–1.14 1.10–1.14 0.00–1.91
(E)-2-Heptenal 18829-55-5 FFA 1,2,4,8,9,10 1.52–1.75 1.54–2.01 1.52–1.88 0.00–2.60   0.00–0.58     1.79–1.97  
(E,E)-2,4-Heptadienal 4313-03-5 FFA 2,8,9,10 0.57–0.66 0.57–0.59 0.00–0.71   Trace 0.00−Coelution        
Octanal 124-13-0 FFA 2,7,8,9,10 0.00–0.62   0.00–0.68     0.00–0.58 1.35–1.76 2.07–2.40 1.15–1.29 0.08–2.22
(E)-2-Octenal 2548-87-0 FFA 1,3,7,8,9,10       3.00–13.10   0.00–0.10 2.13–2.16 0.23–0.23 0.48–0.51 0.19–0.45
Nonanal 124-19-6 FFA 2,4,6,7,8,9,10 2.11–3.08 2.42–2.80 2.13–3.60   1.30 3.12–5.24 3.70–4.60 9.8–12.31 7.99–10.54 3.54–36.29
(E)-2-Nonenal 18829-56-6 FFA 2,7,9,10 0.00–0.67 0.00–0.58           0.20–0.26   0.14–2.52
4-Oxononanal 74327-29-0               0.72–0.91      
(E,E)-2,4-Nonadienal 5910-87-2 FFA 7,9,10             0.00–0.44      
Decanal 112-31-2 FFA 2,7,10 0.81–1.59 0.00–1.06 0.72–0.99   Coelution Coelution−1.33 1.28–1.33 2.86–3.26 1.15–1.41 0.37–6.16
(Z)-2-Decenal 2497-25-8 FFA 7,10             0.79–1.15      
(E,E)-2,4-Decadienal 25152-84-5 FFA 3,7,9,10         Trace          
Undecanal 112-44-7                 0.22–0.26   0.00–1.61
Dodecanal 112-54-9                     0.00–0.89
Tetradecanal 124-25-4           0.63   0.26–0.55     0.00–0.39
Total     24.42–28.01 18.19–23.57 25.77–33.33 10.70–17.70 3.02 40.21–63.66 12.41–12.91 29.14–36.39 58.05–60.58 9.19–79.03
1 [26]; 2 [25]; 3 [27]; 4 [28]; 5 [30]; 6 [31]; 7 [32]; 8 [35]; 9 [12]; 10 [33][34]; 11 [36]. FFA, free fatty acids; AA, amino acids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], “Location” corresponds to different low-tannin cultivars that were harvested at 2 different locations in Canada [31], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) for 60 days and a control (sample stored for 0 days) [32] (see Table 1 for more details).
Table 4. Alkanes/alkenes in pulses (expressed as percentages).
Table
Alkanes/Alkenes CAS Origin (s) Black
Bean		 Pinto
Bean		 Dark Red
Kidney Bean		 Pea Chickpea Faba Bean
Whole Dehulled Proteins Tannin Location Storage
Trichloromethane 67-66-3 N 1       0.00–0.50            
Octylcyclopropane 1472-09-9   0.00–0.96 0.00–1.28 0.00–2.04              
Pentane 109-66-0 FFA 4               0.10–0.10    
Hexane 110-54-3 FFA 4 0.74–1.54 1.14–1.72 0.83–0.86              
3-Methylhexane 589-34-4         0.00–2.50            
Butylcyclohexane 1678-93-9   0.00–0.49 0.00–0.51                
Heptane 142-82-5 FFA 3 0.54–1.15 0.94–1.07 0.57–0.76           0.55–0.56  
Octane 111-65-9 FFA 4 1.74–2.66 0.00–1.74 1.89–3.64           1.79–1.96  
2,6-Dimethyloctane 2051-30-1   0.00–0.48 0.46–0.83                
Nonane 111-84-2 FFA 4 0.75–0.95 1.00–1.37 0.77–1.17         0.16–0.17 0.34–0.36  
3-Methylnonane 5911-04-6   0.00–0.52 0.56–0.80                
4-Methylnonane 17301-94-9   0.00–0.94 0.95–1.64                
3,7-Dimethylnonane 17302-32-8                 0.18–0.19    
Decane 124-18-5 FFA 2,4 2.66–4.27 4.78–6.55 1.60–1.86         0.67–0.70   0.95–3.88
4-Methyldecane 2847-72-5   0.00–0.75 0.64–1.34                
2,4-Dimethyldecane 2801-84-5                     0.00–0.32
3,7-Dimethyl-decane 17312-54-8               0.00–0.31      
Undecane 1120-21-4 FFA 1,4 0.00–0.87 1.06–1.51   1.80–2.60       0.15–0.15 1.36–1.52  
Dodecane 112-40-3   0.00–1.12 1.22–1.27   0.80–3.60       0.57–0.62   0.80–3.22
2,4-Dimethyldodecane 6117–99–3 FFA 1               0.09–0.09   0.00–0.33
5,8-Diethyldodecane 24251-86-3                 0.04–0.06    
2,6,10-Trimethyldodecane 3891-98-3   0.00–0.79 0.64–1.27                
Tridecane 629-50-5         0.90–4.30       0.06–0.08   0.00–0.15
2-Methyltridecane 1560-96-9 FFA 1               0.05–0.05   0.00–0.14
3-Methyltridecane 6418-41-3 FFA 1               0.12–0.15   0.00–0.42
2,2-Dimethyltridecane 61869-04-3                 0.13–0.15    
Tetradecane 629-59-4         0.00–1.10 Trace 0.00–1.10   1.30–1.90   0.48–1.34
Pentadecane 629-62-9             0.00–1.57   0.19–0.21   0.00–0.64
3-Methylpentadecane 2882-96-4                 0.15–0.26   0.00–0.08
Hexadecane 544-76-3             0.00–2.75   0.24–0.26   0.00–0.35
Heptadecane 629-78-7           1.27     0.07–0.10    
Nonadecane 629-92-5                 0.02–0.06   0.46–0.99
Tetracosane 646-31-1               0.00–0.57      
Total alkanes     7.84–15.66 16.43–20.00 7.95–8.09 7.30–14.30 1.27 0.00–5.44 0.31–0.57 4.37–5.22 4.06–4.41 4.61–9.22
(E)-5-(Pentyloxy)-2-pentene 34061-80-8             0.00–0.69        
(Z)-1-Methoxy-3-hexene 70220-06-3               0.00–1.91      
3-Ethyl-2-methyl-1,3-hexadiene 61142-36-7             0.00–0.05     0.37–0.42  
1-Tetradecene 1120-36-1           5.74 0.00−Coelution   0.07–0.08    
Total alkenes             5.74 0.05–0.69 0.00–1.91 0.07–0.08 0.37–0.42  
1 [26]; 2 [25]; 3 [31]; 4 [33][34]. N, naturally present (not considered as a contaminant); FFA, free fatty acids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], “Location” corresponds to different low-tannin cultivars that were harvested at 2 different locations in Canada [31], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) for 60 days and a control (sample stored for 0 days) [32] (see Table 1 for more details).
Table 5. Alcohols in pulses (expressed as percentages).
Table
Alcohols CAS Origin (s) Black
Bean		 Pinto
Bean		 Dark Red Kidney Bean Pea Chickpea Faba Bean
Whole Dehulled Proteins Tannin Location Storage
Ethanol 64-17-5 AA 5
FFA 9,10,11		               0.48–1.29   0.00–0.42
2-Phenylethanol 60-12-8 AA 5,7,11               0.27–0.34   0.00–0.83
2-Butoxyethanol 111-76-2           0.95 0.00–0.88        
2-Phenoxyethanol 122-99-6           Coelution 0.00−Coelution       0.00–0.30
Propanol 71-23-8 AA 1
FFA 9,10		       0.60–1.30       0.48–0.53   0.00–0.64
2-Propanol 67-63-0                 0.48–0.57   0.00–0.15
1,2-Propanediol 57-55-6             0.00–0.04        
2-Methylpropanol 78-83-1 AA 9,11       0.00–0.50            
1-Methoxy-2-Propanol 107-98-2               0.00–0.28      
2-Phenyl-2-propanol 617-94-7                   0.38–0.41  
1-[1-Methyl-2-(2-propenyloxy)ethoxy]-2-propanol 55956-25-7             0.00–0.09        
Butanol 71-36-3 FFA 9,10             4.32–4.72      
2-Butanol 78-92-2                 1.29–1.38   0.00–1.90
2-Methylbutanol 137-32-6 AA 5,8,9,11           0.06–0.34   3.52–4.80   0.38–5.48
3-Methylbutanol 123-51-3 AA 5,7,8,9,11 0.00–0.80 0.58–0.86     0.42 0.06–0.22   1.97–2.43   0.12–3.23
3-Phenyl-2-butanol 52089-32-4               0.00–1.23      
2,3-Butanediol 513-85-9                 0.39–0.40   0.00–1.72
Pentanol 71-41-0 FFA 2,3,4,7,8,9,10 0.00–1.61 0.00–0.62     1.52 1.17–3.89 4.90–4.98 1.28–1.36 1.85–2.29 0.74–1.57
2-Pentanol 6032-29-7 FFA 9         0.23     0.18–0.27   0.00–0.46
3-Methyl-3-pentanol 77-74-7           5.34 0.00–0.60        
1-Penten-3-ol 616-25-1 FFA 2,3,4,8,9,10 0.99–1.86 1.34–1.88 2.30–2.64   6.87 0.44–5.58        
2-Penten-1-ol 20273-24-9             0.00–3.84        
5-[3-(4-Methoxyphenyl)-2-oxaziridinyl]-1-pentanol -               0.33–0.90      
Phenol 108–95–2   0.00–0.47 0.31–0.34       0.00−Coelution 0.54–0.70      
Benzyl alcohol 100-51-6 AA 5,11 0.00–0.24 0.26–1.11       0.00−Coelution   0.54–0.54   0.58–1.46
Hexanol 111-27-3 FFA 2,3,4,6,7,8,9,10 1.58–1.86 1.39–1.60 1.24–1.25   4.54 0.88–9.53   10.64–11.32 3.87–4.29 0.33–31.41
2-Ethylhexanol 104-76-7   0.29–0.45 0.29–0.66 0.00–0.4     0.00–1.39       0.00–9.38
4-Ethylcyclohexanol 4534-74-1                 0.15–0.17    
2,3-Dimethylcyclohexanol 1502-24-5                     0.00–0.20
1-Hexen-3-ol 4798-44-1           0.29 0.00–0.14        
(Z)-3-Hexen-1-ol 928-96-1 FFA 8,9         4.23 0.00–0.29        
(Z)-4-Hexen-1-ol 928-91-6             0.00–0.33        
Heptanol 111-70-6 FFA 8,9,10       0.00–1.20 Coelution Coelution−0.66   0.32–0.36 0.50–0.54 0.00–0.26
2-Heptanol 543-49-7 FFA 9       0.00–0.40            
2-Methyl-3-heptanol 18720-62-2           0.72          
3-Methyl-2-heptanol 31367-46-1         0.00–2.40            
2-Hepten-4-ol 4798-59-8               0.00–0.78      
Octanol 111-87-5 FFA 3,7,8,9,10 0.00–0.33 0.29–0.61 0.00–0.29 3.7–10.7 1.16 0.82–1.29   0.24–0.28 1.18–1.48 0.35–0.83
3-Octanol 589-98-0 FFA1       0.00–1.3           0.00–0.42
1-Octen-3-ol 3391-86-4 FFA 2,3,4,6,7,8,9,10 1.18–1.43 1.23–1.60 0.00–3.51   2.61 1.23–1.38   0.35–0.41 3.93–4.00 0.29–1.64
(E)-2-Octen-1-ol 18409-17-1 FFA 10           0.00–0.96     0.37–0.41  
(E,E)-3,5-Octadien-2-ol 69668-82-2                 0.10–0.14    
Nonanol 143-08-8 FFA 7 0.42–1.30 0.92–1.10 0.00–0.43   1.27 0.00–2.69   0.92–1.14 0.28–0.41 0.85–1.74
Decanol 112-30-1                 0.22–0.29    
Undecanol 112-42-5           6.18         0.00–0.09
2-Pentadecyn-1-ol 2834-00-6               0.00–0.55      
Total     6.13–7.72 8.05–9.04 4.67–7.41 7.40–12.70 36.33 8.22–30.70 11.22–13.01 24.21–27.63 13.00–13.27 4.34–53.01
1 [26]; 2 [25]; 3 [27]; 4 [28]; 5 [30]; 6 [31]; 7 [32]; 8 [35]; 9 [12]; 10 [33][34]; 11 [36]. AA, amino acids; FFA, free fatty acids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], “Location” corresponds to different low-tannin cultivars that were harvested at 2 different locations in Canada [31], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) for 60 days and a control (sample stored for 0 days) [32] (see Table 1 for more details).
Table 6. Ketones in pulses (expressed as percentages).
Table
Ketones CAS Origin (s) Black
Bean		 Pinto
Bean		 Dark Red
Kidney Bean		 Pea Chickpea Faba Bean
Whole Dehulled Proteins Tannin Location Storage
Acetophenone 98-86-2 AA 5; FFA 6 0.63–0.98 0.53–0.77 0.00–0.82         0.33–0.36   0.00–0.50
p-Isopropylacetophenone 645-13–6             0.00–0.73       0.15–0.57
p-Acetylacetophenone 1009-61-6                     0.19–0.29
Acetone 67-64-1 FFA 5 0.66–1.47 0.85–1.12 1.16–1.75         1.99–2.46 1.00–1.02 0.41–0.92
Butanone 78-93-3 FFA 1,2,6 0.00–0.41 0.00–0.38   0.00–0.50   0.00–0.97   3.20–3.43 0.58–0.67 0.79–4.82
3-Hydroxy-3-methyl-2-butanone 115-22-0             0.00−Coelution        
Pentanone 107-87-9 FFA 1,6       0.00–1.20            
3-Pentanone 96-22-0           0.87          
2,3-Pentanedione 600-14-6 FFA 6         0.42 0.00–1.05        
Hexanone 591-78-6 FFA 6               0.03–0.04    
Cyclohexanone 108-94-1             0.00–0.15        
5-Hexen-2-one 109-49-9           3.29 0.00–1.75        
6-Methyl-5-hepten-2-one 110-93-0 FFA 2; CAR 4 1.97–2.45 0.94–1.76 1.27–2.44       0.82–0.87 1.08–1.50 1.06–1.09 0.00–1.27
Heptanone 110-43-0 FFA 3,6         0.17 0.25–1.03   0.27–0.32 0.46–0.48 0.24–0.35
2-Methyl-3-heptanone 13019-20-0           6.85 0.00–6.50        
Isobutyl-2-heptenone -             0.00–0.17        
Octanone 111-13-7 FFA 6         0.41          
3-Octanone 106-68-3 FFA 4,6         Trace          
3-Octen-2-one 1669-44-9 FFA 5           0.28–0.83     0.69–0.86  
2,3-Octanedione 585-25-1           Trace 0.00–1.34 1.71–2.00   0.52–0.53  
(E,E)-3,5-Octadien-2-one 30086-02-3 FFA 2,5 1.14–1.98 1.31–2.41 1.42–1.46     0.00–8.00   0.20–0.28   0.16–0.20
Nonanone 821-55-6                 0.26    
Decanone 693-54-9             0.00–0.35        
1,6-Dioxacyclododecane-7,12-dione 777-95-7               0.00–0.72      
Undecanone 112-12-9           Trace 0.00–0.18        
2-Butyl-1,3,2-dioxaborinan-4-one 33823-94-8               0.00–0.37      
Total     4.95–6.90 4.74–5.38 4.73–5.62 0.50–1.20 12.01 1.69–21.96 3.24–3.25 7.59–8.42 4.48–4.53 3.72–7.46
1 [26]; 2 [31]; 3 [32]; 4 [35]; 5 [12]; 6 [33][34]. AA, amino acids; FFA, free fatty acids; CAR, carotenoids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], “Location” corresponds to different low-tannin cultivars that were harvested at 2 different locations in Canada [31], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) for 60 days and a control (sample stored for 0 days) [32] (see Table 1 for more details).
Table 7. Acids in pulses (expressed as percentages).
Table
Acids CAS Origin (s) Pea Chickpea Faba Bean
Dehulled Proteins Tannin Storage
Acetic acid 64-19-7 AA 2,3,4     3.10–3.90 1.84–2.35 0.49–1.94
2-Methylbutanoic acid 116-53-0 N 1; AA 1,2,4   0.00–0.22   0.13 0.00–0.26
3-Methylbutanoic acid 503-74-2 AA 2,3,4 0.42 0.00–0.41   8.79–12.37 2.55–10.36
Pentanoic acid 109-52-4   0.48        
Hexanoic acid 142-62-1 FFA 1 0.73 0.00−Coelution 1.06–1.98 0.57–1.54  
2-Ethyl hexanoic acid 149-57-5   0.51 0.00–0.43      
Heptanoic acid 111-14-8   1.46        
Octanoic acid 124-07-2 N 1; FFA 3 1.54 0.00−Coelution     0.00–0.24
Nonanoic acid 112-05-0 FFA 3 1.92 0.00–1.40     0.00–0.58
Decanoic acid 334-48-5       0.00–0.89    
Palmitic acid 57-10-3       12.00–15.00    
Oleic acid 112-80-1       11.00–24.00    
Total     7.07 0.63–1.84 32.77–40.16 11.33–16.39 3.24–13.15
1 [27]; 2 [30]; 3 [32]; 4 [36]. AA, amino acids; N, naturally present (not considered as a contaminant); FFA, free fatty acids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. For peas, “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) for 60 days and a control (sample stored for 0 days) [32]. No acid was detected in black beans, pinto beans, red kidney beans, whole peas, and “location” faba beans (see Table 1 for more details).
Table 8. Esters in pulses (expressed as percentages).
Table
Esters CAS Origin (s) Black
bean		 Pinto
Bean		 Dark Red
Kidney Bean		 Pea Chickpea Faba Bean
Whole Dehulled Proteins Tannin Storage
Ethyl ethanoate 141-78-6 FFA 3       0.00–1.20          
2-Ethylhexyl ethanoate 103-09-3                   0.00–0.79
Butyl ethanoate 123-86-4                   0.00–0.25
Hexyl ethanoate 142-92-7 FFA 2                 0.00–2.96
Ethyl cyanoacetate 105-56-6               0.00–0.39    
Decyl bromoacetate 5436-93-1   0.00–0.36 0.00–0.32 0.00–0.34            
1,2-Dihydro-2-naphtalenylacetate -               0.80–1.06    
Ethyl propanoate 105-37-3           Coelution 0.00–17.19      
Octyl pivalate -                   0.00–0.76
Hexyl 2-methylbutanoate 10032-15-2                   0.00–3.54
Ethyl butanoate 105-54-4           0.93 0.00–0.05     0.00–3.66
2-Ethylhexyl butanoate 25415-84-3                   0.00–0.92
Methyl isovalerate 556-24-1 AA 1                 0.00–2.11
Isoamyl isovalerate 659-70-1                   0.00–0.51
Butyl hexanoate 626-82-4                   0.00–7.48
2-Propenyl hexanoate 123-68-2           0.82        
Hexyl hexanoate 6378-65-0                   0.00–3.33
Octyl hexanoate 4887-30-3             0.00–1.75      
Methyl salicylate 119-36-8                 0.04–0.05 0.00–0.50
5-Isobutylnonane 62185-53-9               0.00–3.10    
4-Dodecanoyloxybutyl dodecanoate 624-07-7               0.00–0.77    
Isopropyl myristate 110-27-0               0.44–0.53    
3-Hydroxy-ethyl mandelate -   0.28–0.42 0.34–0.45 0.00–0.42            
Total     0.42–0.66 0.45–0.66 0.00–0.77 0.00–1.20 1.75 1.75–17.25 1.50–5.59 0.04–0.05 0.00–24.15
1 [32]; 2 [35]; 3 [34]. FFA, free fatty acids; AA, amino acids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and to protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) during 60 days and a control (sample stored for 0 days) [32]. No ester was detected in “location” faba beans (see Table 1 for more details).
Table 9. Pyrazines in pulses (expressed as percentages).
Table
Pyrazines CAS Origin (s) Pea
Whole Dehulled Protein
2,3-Diethyl-5-methylpyrazine 18138-04-0   0.00–1.30    
2-Methyoxy-3-isopropyl(5or6)-methylpyrazine 32021-41-3 AA 1   2.62 0.00–0.13
2-Methoxy-3-isobutylpyrazine 24683-00-9 AA 2   Trace  
Total     0.00–1.30 2.62 0.00–0.13
1 [27]; 2 [37]. AA, amino acids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. No pyrazine was detected in black beans, pinto beans, dark red kidney beans, chickpeas, and faba beans (“tannin”, “location”, and “storage”) (see Table 1 for more details.).
Table 10. Terpenes in pulses (expressed as percentages).
Table
Terpenes CAS Origin (s) Black
Bean		 Pinto
Bean		 Dark Red
Kidney Bean		 Pea Faba Bean
Whole Dehulled Proteins Tannin Storage
α-Pinene 80-56-8 CAR 1,2 1.37–2.29 2.11–3.92 0.75–1.07          
Δ3-Carene 13466-78-9 CAR 1,2 0.00–0.50 0.00–0.48   0.30–0.70        
Limonene 138-86-3 CAR 1,2 0.00–1.36 1.31–2.96     0.66 0.00–0.11 0.96 0.00–10.81
γ-Terpinene 99-85-4                 0.00–0.79
Terpinolene 586-62-9                 0.00–0.12
Thujospsene-I3 -                 0.00–0.09
(E)-β-Ionone 79-77-6 CAR 3             0.11–0.12  
β-Myrcene 123-35-3 CAR 2               0.00–0.60
Geranylacetone 689-67-8   0.00–0.69   0.00–0.30          
Elemol 639-99-6           2.71      
α-Muurolol 19435-97-3           2.94      
t-Muurolol 19912-62-0           7.45      
α-Cadinol 481-34-5           Coelution      
β-Eudesmol 473-15-4           Trace      
β-Linalool 78-70-6                 0.11–0.79
Menthol 1490-04-6               0.28–0.45 0.00–0.60
p-Menth-1,5-dien-8-ol 1686-20-0           Coelution      
Total     2.06–4.77 3.91–6.89 1.06–1.07 0.30–0.70 13.77 0.00–0.11 1.35–1.63 0.11–12.73
1 [26]; 2 [35]; 3 [12]. CAR, carotenoids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) during 60 days and a control (sample stored for 0 days) [32]. No terpene was detected in chickpeas and “location” faba beans (see Table 1 for more details).
Table 11. Furans in pulses (expressed as percentages).
Table
Furans CAS Origin (s) Black Bean Pinto Bean Dark Red
Kidney Bean		 Pea Faba Bean
Whole Dehulled Proteins Tannin Location Storage
2-Methylfuran 534-22-5 FFA 3       0.00–1.80          
2-Ethylfuran 3208-16-0 FFA 1,5 0.00–0.64 0.62–0.74 0.00–0.58 0.00–3.90       0.29–0.29  
2-Acetylfuran 1192-62-7           Coelution 0.00–Trace      
2-Propylfuran 4229-91-8   0.53–0.71 0.49–0.61 0.75–0.85            
2-Propionylfuran 3194-15-8   0.44–0.66 0.00–0.78 0.53–0.69            
2-Pentylfuran 3777-69-3 FFA 2,3,4,5           0.00–0.91 0.60–0.78 1.72–1.91 0.61–1.43
Total     1.37–1.64 1.23–2.02 1.43–1.97 0.00–5.70   0.00–0.91 0.60–0.78 2.02–2.21 0.61–1.43
1 [31]; 2 [28]; 3 [32]; 4 [35]; 5 [33]. FFA, free fatty acids. The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond to 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], “Location” corresponds to different low-tannin cultivars that were harvested at 2 different locations in Canada [31], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) for 60 days and a control (sample stored for 0 days) [32]. No furan was detected in chickpeas (see Table 1 for more details).
Table 12. Lactones in pulses (expressed as percentages).
Table
Lactones CAS Origin (s) Pea Chickpea Faba Bean
Dehulled Proteins Tannin Storage
γ-Butyrolactone 96-48-0       0.00–0.85 0.32–0.63 0.22–1.08
3-Methylbutyrolactone 1676-49-8   0.45        
4-Methyl-4-vinylbutyrolactone 1073-11-6         0.08–0.09  
Pentolactone 599-04-2       2.20–2.30    
γ-Pentalactone 108-29-2   1.01        
δ-Caprolactone 823-22-3 N 2       0.24–0.26 0.00–0.82
γ-Caprolactone 695-06-7 N 2 10.11 0.00–Coelution   0.34–0.36 0.00–1.07
γ-Methyl-γ-caprolactone 2865-82-9   1.16 0.00–1.63      
4-Hydroxy-2-hexenoic acid lactone 2407-43-4     0.00–0.17      
γ-Octalactone 104-50-7 FFA 1 Trace 0.00-Trace      
γ-Nonalactone 104-61-0 FFA 1 1.31 0.00–0.33      
4-Hydroxy-2-noneic acid lactone 21963-26-8 FFA 1 0.72 0.00–1.04      
δ-Undecalactone 710-04-3 N 2     0.00–0.47 0.19–0.20  
Total     14.76 0.00–3.18 2.30–3.52 1.21–1.50 0.22–2.47
1 [27]; 2 [30]. FFA, free fatty acids; N, naturally present (not considered as a contaminant). The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. For peas, “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) during 60 days and a control (sample stored for 0 days) [32]. No lactone was detected in black beans, pinto beans, dark red kidney beans, whole peas, and “location” faba beans (see Table 1 for more details).
Table 13. Other volatiles in pulses (expressed as percentages).
Table
Other Volatiles CAS Black
Bean		 Pinto
Bean		 Dark Red
Kidney Bean		 Pea Chickpea Faba Bean
Whole Dehulled Proteins Tannin Storage
Estragole 140-67-0                 0.00–0.16
Benzothiazole 95-16-9         0.42 0.00–1.50 0.00–0.30    
4,5-Dimethylimidazole 2302-39-8             0.00–1.22    
Dimethyl sulphide 75-18-3       0.86–3.30          
Dimethyl disulphide 624-92-0       0.00–0.80          
3-Phenylindole 1504-16-1 0.00–0.84 0.49–1.18 0.72–0.73            
Methoxy-phenyl-oxime - 0.43–0.88 0.00–0.62 0.00–0.72         3.39–3.60  
2,4-Dimethylbenzenamine 95-68-1 0.00–0.26 0.00–0.25 0.00–0.35            
2-(Trimethylsilylethynyl)pyridine 86521-05-3             0.00–0.40    
Total   0.72–1.72 1.18–1.37 0.72–1.80 1.26–3.40 0.42 0.00–1.50 0.00–1.92 3.39–3.60 0.00–0.16
The value “min–max” corresponds to the minimum and maximum percentages for each volatile compound identified. “Black bean” refers to the 3 cultivars studied, and “Pinto bean” and “Dark red kidney bean” correspond 2 cultivars for each [25]. For peas, “Whole” corresponds to 3 different harvest years of the cultivar Eclipse (2005, 2006, and 2007) [26], “Dehulled” corresponds to dehulled pea flour [27], and “Protein” refers to protein concentrate (dry process) [28] and protein isolate (wet process) [27]. “Chickpea” refers to 2 cultivars [29]. For faba beans, “Tannin” corresponds to a group of low-tannin cultivars and a group of high-tannin cultivars [30], and “Storage” corresponds to high-tannin cultivars that were stored under 3 different conditions (ambient, positive, and negative temperatures) during 60 days and a control (sample stored for 0 days) [32]. No other volatile was detected in “location” faba beans (see Table 1 for more details).

5. Odour-Active Compounds in Pulses

An odour-active compound is a volatile compound whose concentration is greater than or equal to its odour detection threshold. It contributes to the product’s aroma. These compounds can be detected by GC-O.
In dehulled peas, 15 odour-active compounds are present compared to 16 in pea protein isolates, and they are related to different types of odour descriptors, such as mushroom/earth, vegetable/green/pea, empyreumatic (peanut-grilled), animal, floral/fruity, and sweet [27]. For lupin, 19 odour-active compounds (including an unknown volatile) were identified in whole grains and 26 in dehulled grains. These volatiles are described as sweet, beany/pea/green/cardboard, floral, mushroom, fruity/floral, and animal [38][39]. Odour-active compounds are distributed into aldehydes, alcohols, ketones, acids, lactones, and pyrazines; however, aromatic hydrocarbons, alkanes, alkenes, esters, terpenes, and furans are not involved in the aroma of these pulses. The origin of these compounds is free fatty acid oxidation, except for acids and pyrazines, which are derived primarily from amino acid degradation.
Dehulled peas and pea isolates share the following odourant compounds: vanillin, hexanal, (E,E)-2,4-decadienal, 1-octen-3-ol, 2,3-octanedione, undecanone, γ-octalactone, 4-hydroxy-2-noneic acid lactone, 5- or 6-methyl, and benzothiazole. Some compounds are not detected in whole peas but are active compounds in pea protein isolates, such as 4-ethybenzaldehyde, phenylacetaldehyde, 3-methylthiopropanal, heptanal, (E)-2-octenal, (E,E)-3,5-octadien-2-one, heptanoic acid, and dimethyl trisulfide; they mainly come from free fatty acids and amino acids. However, nonanal, pentanol, octanol, nonanol, 3-methylbutanoic acid, and γ-nonalactone are only active in dehulled peas; they mainly come from free fatty acid oxidation. Curiously, nonanal, pentanol, and octanal are more concentrated in volatile extracts of pea protein isolates than dehulled peas but are only perceived as odour-active in dehulled samples.
Whole and dehulled lupins have only a few odour-active compounds in common: (E)-2-nonenal, (E,Z)-2,6-nonadienal, 1-octen-3-one, 3-isobutyl-2-methoxypyrazine, and 3-isopropyl-2-methoxypyrazine. Many compounds from amino acids are only present in dehulled lupin, such as 2-acetyl-1-pyrroline, maltol, sotolone, and some acids. They are probably due to contamination by microorganisms in these grains.
Vanillin and  gama-octalactone are odour-active compounds in peas and dehulled lupins. Gama-octalactone is described as floral/anise/mint in peas and coconut/sweet in lupins. Hexanal is not an odourant only in dehulled peas. Pea protein isolates and whole lupins have two odourant compounds in common: (E)-2-octenal and dimethyl trisulfide; this last compound is described as faeces/meat broth/sewer in peas and meaty/metallic/sulphur in lupins. 3-Methylbutanoic acid and  -nonalactone are odour-active compounds of whole peas and dehulled lupins; 3-methylbutanoic acid is perceived as animal in peas but sweaty/fruity/cheesy in lupins. These differences are not necessarily due to the variety of pulses; the descriptors depend on the panellists, the possible presence of coelution, or large differences in the volatile concentrations.
Odour-active compounds present in peas and lupins are derived mainly from free fatty acids and amino acids. The large variety of these perceived volatiles depends on the type of pulses, the cultivar, the storage conditions, and the transformation steps. Finally, descriptors for the same molecule could be very different and depend on the studied matrix.

6. Conclusions and Perspectives

A qualitative comparison of volatile compounds between pulses is presented. Indeed, the main drawback to making quantitative comparisons of volatiles is that the data are often expressed as peak areas or relative percentages, without using a standard compound allowing real quantification of each volatile compound. However, it was possible to suggest some hypotheses on the origins of the off-notes present in pulses with the aim of increasing the acceptability of pulses in food for humans.
The diversity of unsaturated free fatty acid contents and the characteristics of endogenous lipoxygenases in pulses mainly explain the large variety of volatile compounds identified. All of the classes of volatiles are present in pulses, but ketones, pyrazines, furans, and lactones are minority classes. Aromatic hydrocarbons represent more than 38% of the volatiles detected in common beans (black beans, pinto beans, and dark red kidney beans), whereas aldehydes and alcohols are more specific to dehulled peas, pea proteins (concentrate and isolate), and faba beans (location and storage). Seed transformations or uncontrolled parameters of storage promote the generation of volatile compounds from the degradation of free fatty acids and amino acids. For whole peas, the 2006 harvest-year seeds present higher percentages of aromatic hydrocarbons, aldehydes, alkanes, ketones, and furans than those of the 2005 and 2007 seeds [13]. If the storage conditions are supposed to be equivalent for these three harvest years, bad culture conditions could be suggested during 2006, such as water stress and/or mechanical or insect attacks, compared to years 2005 and 2007 and could explain these differences in terms of volatiles. Finally, all of these parameters could account for such heterogeneity in volatile compounds, yet they are not always taken into consideration in explaining the variability in aromatic composition.
Although the number of volatile compounds identified in pulses is high, only a small part contributes to the aroma. These odour-active compounds present different descriptors and threshold detection. However, identifying odour-active compounds in pulses is rarely done, and only two studies report on their olfactory impact, namely in lupins and peas. Only aldehydes, alcohols, ketones, acids, lactones, and pyrazines are involved in the aroma. The origin of these compounds is free fatty acid oxidation, except for acids and pyrazines, which originate primarily from amino acid degradation by unwanted microorganisms. Off-notes are described as vegetable, green, hay, potato, bean, metallic, mushroom, animal, dust, solvent, cardboard, etc., and refer to “beany” notes, but other volatiles present a pleasant smell, such as floral, fruity, grilled, sweet, and vanilla odours.
Precise identification of the odour-active compounds in pulses could allow the determination of their main origins and the proposal of strategies to reduce their perception. Some strategic axes have been identified to improve pulses’ aroma: to limit the production of volatile compounds, to remove the off-notes, and to decrease the perception of off-notes [40][41]. One approach consists of generating lipoxygenase-free legume seeds to limit off-note production, and this experiment was carried out on soybeans[42]. However, volatiles provided by the LOX pathway are also fully involved in a mechanism of defence for plants[43]. Therefore, a potential lower resistance of mutated plants should be considered. Moreover, due to climate change, water stress, or other stressors increase in future years, these new cultivars could be less adapted and produce lower yields. Moreover, heat treatments, such as blanching, microwave, radiofrequency, and conventional heating of mature seeds, allow the decrease or inhibition of lipoxygenase activity [44][45]. However, high temperatures favour the autoxidation of unsaturated free fatty acids. A compromise must be considered to limit these two phenomena. Finally, for the past 20 years, fermentation has modified the aroma profile of pulses by reducing or masking off-notes. Some molecules are still detected, such as pentanal, hexanal and heptanal in fermented lupin proteins or 2,3-butanedione, hexanal, 1-penten-3-one,2-heptanone, and 3-methylbutanol in fermented pea proteins [46][47]. A perspective that must be studied is the use of microorganism coculture to improve the aroma of pulses [48]. Another approach could consist of using perceptual interactions to mask off-notes or modify the aroma product to a pleasant product, in particular using odour-mixture, odour-taste, and/or odour-texture interactions [49][50].
Furthermore, non-volatile compounds also contribute to the off-flavours of pulses, particularly for bitterness and astringency (off-tastes). Saponins, alkaloids, and phenolic compounds have been identified in pulses, but their role in sensorial perception has rarely been studied. The elimination of these molecules could increase the acceptability of plantbased products.

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