Identification of aroma compounds in raw and cooked broccoli

Abstract

Broccoli is characterized by its specific flavor, which is the reason it is not tolerated by some consumers. The role of aroma in flavor is crucial; however, the characteristics of aroma‐active components in broccoli are still unclear. Solvent‐assisted flavor evaporation (SAFE) with the aid of solid‐phase microextraction (SPME) and fractionation using solid phase extraction (SPE), followed by different chromatography‐mass spectrometry approaches (GC‐MS, GC‐MS/MS, GC×GC‐ToFMS) were used to identify the compounds of interest. A total of 33 aroma‐active compounds were detected with the use of gas chromatography‐olfactometry (GC‐O) in raw, and 9 in cooked broccoli florets; in majority sulfur compounds—thiols, sulfides, and isothiocyanates prevailed. Methanethiol and 1‐pentanethiol were the key odorants characterized by the highest FD (1024) in raw broccoli, followed by dimethyl sulfide, 2,3‐butanedione, dimethyl trisulfide, dimethyl tetrasulfide, 2‐methyl methanethiosulphonate, 4‐methylpentyl isothiocyanate, hexyl isothiocyanate (all with an FD of 256). In cooked broccoli, the number and especially the intensity of detected compounds were much lower. The highest FD values (FD=4) were noted for dimethyl trisulfide and 1,4‐octadien‐3‐one. To our knowledge, this is the first detailed identification of odorants in raw and cooked broccoli.

Valorisation of Broccoli By-Products: Technological, Sensory and Flavour Properties of Durum Pasta Fortified with Broccoli Leaf Powder

“…Although the VOCs in Brassica vegetables have been widely studied [ 38 , 39 , 40 , 41 ], in this study, the profile of broccoli leaves was analysed for the first time. Previous studies showed that the analysis of fresh vegetables resulted in a high abundance of sulphur compounds, including isothiocyanates derived from glucosinolates, which are responsible for a cabbage-like aroma [ 38 , 39 ].…”

“…An important compound responsible for sulphur aroma is dimethyl sulphide. Although its abundance was low in BLP and did not differ between pastas B2.5 and 5, this compound was previously reported to be one of the key odorants in Brassica vegetables [ 41 ]. Importantly, the odour threshold of dimethyl sulphide is very low and was estimated as 0.0008–0.03 and 0.0003–0.16 mg kg −1 in water and air, respectively [ 42 ].…”

“…Importantly, the odour threshold of dimethyl sulphide is very low and was estimated as 0.0008–0.03 and 0.0003–0.16 mg kg −1 in water and air, respectively [ 42 ]. Low odour thresholds indicate odours are detectable at extremely low concentrations—very often below the limit of detection [ 41 ]. Therefore, despite its low abundance, it can be assumed that this compound was responsible for the cabbage-like aroma detected by the sensory panel.…”

“…Cabbage flavour detected in pasta B5 could be attributed to the presence of dimethyl sulphide, which was reported to have a high flavour dilution (FD), suggesting that even a small concentration of this compounds contributes to its overall aroma. Because panellists detected a difference in the intensity of cabbage-like aroma between pasta B2.5 and B5, it can be assumed that other sulphur compounds, which usually have relatively low odour thresholds, could be present below the limit of detection [ 41 ]. The absence of high-molecular-weight sulphides, such as dimethyl, tri- and tetrasulphides, may be related to the fact that the SPME technique, as an absorption method, is more suitable for the extraction of low-molecular-weight compounds.…”

Current Methods for the Extraction and Analysis of Isothiocyanates and Indoles in Cruciferous Vegetables

“…The determination of ITCs with GC-MS has been employed [104][105][106][107][154][155][156]. For the analysis of volatile ITCs, the eco-friendly technique of Solid Phase Microextraction (SPME) in conjunction with GC-MS has been also proposed [157][158][159][160][161]. A method employing GC-MS with a pre-column derivatization step has been also developed by Latxague et al [26].…”