Distribution of glucosinolate and pungent odors in rapeseed oils from raw and microwaved seeds

Abstract

The current study was aimed to investigate the effect of glucosinolate degradation on the flavor precursors and pungent odors in raw and microwaved rapeseeds. Five isothiocyanates and six sulfur compounds were identified using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC× GC-TOF/MS). Comprehensive analysis with headspace solid-phase microextraction (HS-SPME) and aroma extract dilution analysis (AEDA) with altering split ratio showed that 1-isothiocyanato butane, allyl isothiocyanate and 4-isothiocyanato-1-butene were responsible for the sulfur, pungent and green odors in rapeseed oils, due to their high flavor dilution factor. Dimethyl sulfide, dimethyl trisulfide and dimethyl sulfoxide, might be derived from methionine or isothiocyanate rearrangement reactions imparted onion-like, cabbage-like, garlic-like, and sulfurous-pungent odors. Rapeseed samples were heated in a microwave for seven minutes, and the total glucosinolate content decreased from 28.2 ± 0.8 μmol/g to 14.5 ± 0.6 μmol/g in Brassica napus, from 101.2±3.0 μmol/g to 42.2 ± 5.4 μmol/g in Brassica campestris, and from 132.02 ± 9.31 μmol/g to 52.50 ± 6.50 μmol/g in Brassica juncea, compared to untreated ones. Differences in the concentrations of six main odorants and the glucosinolate precursors from genetic types were responsible for the intensity of the pungent odors in raw and microwaved rapeseeds. The result can assist to determine the flavor of the commercial rapeseed oils.

Determination of Origin of Commercial Flavored Rapeseed Oil by the Pattern of Volatile Compounds Obtained via GC–MS and Flash GC Electronic Nose

“…The content of 4‐isothiocyanato‐1‐butene in all Sichuan samples (1710–7229 mg kg –1 , average value was 3008 mg kg –1 ) was higher than the mean level. 4‐Isothiocyanato‐1‐butene (sulfur, pungent, green), owned a high flavor dilution factor and attributed most to the characteristic flavor of the rapeseed oil among glucosinolate degradation products . It was described as an important volatile compound in FRO, with low threshold (0.017 mg kg –1 in water), contributing to the pungent flavor, which may be popular among the residents in Sichuan.…”

Research on the relationship between sensory profile and physicochemical properties of paocai, a Chinese fermented vegetable

“…Some nonthiocyanates esters may also provide flower‐like or sweet aroma (Cha, Kim, & Cadwallader, ; Feng et al, ; Zhang et al, ), these odors increased the sensory score as they were positively correlated with a correlation coefficient of 0.32 ( p < .05). The thiocyanates esters such as allyl isothiocyanate, 4‐methylpentyl isothiocyanate, 1‐isothiocyanato‐hexane are known as the main pungent compounds for many vegetables (Ina et al, ; Matsuoka et al, ; Zhou et al, ) and were negatively correlated with sensory feelings ( p < .05).…”

Study on discrimination of different grades of rapeseed oil based on flavor fingerprint

“…3, different grades of rapeseed oil samples were distributed in the four corners of the PCA diagram. Compared with other VOCs, the feature variables of characteristic substances (markers 5,14,29,13,24,28,36,38,40,42,44,53) were more important compounds, because their positions were further apart from the origin of coordinates. Some characteristic variables that could be used to distinguish first grade and second grade rapeseed oil samples (e.g.…”

“…It is known that glucosinolates are sulfurcontaining secondary metabolites, which widely exist in cruciferae plant. The degradation process of glucosinolates is very complex and the main degradation products are nitriles, nitrogen compounds and sulfur nitrogen compounds, which are the important characteristic flavor compounds in the rapeseed oil and are also the main reason for pungent taste of rapeseed oil [24]. From Table 1, there were 6 kinds of nitriles in the rapeseed oil samples and these substances mainly existed in the third and fourth grade rapeseed oil samples.…”