This study was carried out to explore the possible mechanisms behind the high oxidative stability of roasted mustard seed oil. A potent radical scavenger formed during mustard seed roasting was isolated and identified based on nuclear magnetic resonance, mass spectrometry, ultraviolet and fluorescence spectra. The compound was found to be 2,6-dimethoxy-4-vinylphenol (canolol) and was confirmed by chemical synthesis. The oxidative stability of the sixteen different crude roasted mustard seed oil samples collected from the Nepalese market was evaluated by monitoring the peroxide value (PV) and conjugated diene (CD) during storage at 50 oC (in dark). These samples showed a wide variability in the oxidative stability. Some of the samples were shown to be highly stable even after 69 days of storage reaching PV less than 9 meq oxygen/kg fat. The oxidative stability of the different samples (PV after 40 days of storage (PV40) as an index) was not significantly correlated (p > 0.05) with both the sum of the tocopherols and canolol content of the oil and the total radical scavenging activity of the oil using the DPPH assay. On the other hand, the PV40 was negatively correlated with the absorbance at 350 nm (p < 0.001), fluorescence (excitation at 350 nm and emission at 440 nm) (p < 0.001), phospholipid content (p < 0.001), pyrrolized phospholipid content (p < 0.01) and canolol content (p < 0.01). Moreover, phospholipid content, fluorescence, pyrrolized phospholipid content and absorbance at 350 nm were highly positively correlated (p < 0.001) with each other. The phospholipids and its Maillard type browning reaction products together with canolol were primarily responsible for the high oxidative stability of the roasted mustard seed oil samples.

Novel insight on the high oxidative stability of roasted mustard seed oil

246th National Meeting (2013)

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