| Allyl isothiocyanate (AITC), a pungent flavor substance, is a naturally-occurring flavor found in plants and their products, particularly those from cruciferea family (for example, mustard, wasabi, and horseradish). Using standard AITC, AITC rich vegetable and its products, the methods of qualitative, quantitative determination of AITC, its antimicrobial activity and application to a leaf mustard products, 'Chongcai', were investigated.Firstly, headspace solid-phase microextraction (SPME) was established to determine AITC by orthogonal design. Extraction temperature, stir speed, extraction time, and desorption time were set at 40℃, 900r/min, 30min, and 5min, respectively. Under these optimal conditions, volatile flavor compounds in mustard oil, wasabi, and 'Chongcai'leaf mustard product were identified by SPME/GC/MS. In these three samples, 6,12,17 constituents were identified respectively; Allyl isothiocyanate was the main flavor compound, which accounted for 73.45%, 64.25%, 32.74% of total volatile compounds, respectively. Carbon disulfide, a hydrolysis product of AITC, accounted for 14.37% 25.40%, 51.67% of total volatile compounds respectively. There were some other isothiocycannates, such as butane, 1-isothiocyanato-, isobutyl isothiocyanate, 1-benzene, 4-isothiocyanato-, benzene (2-isothiocyanatoethyl)-, etc.Using mustard oil, mustard paste, and 'Chongcai' leaf mustard product, three trpical AITC rich vegetable products, the ultraviolet spectrophotometry, titration analysis of AgNO3 and thiourea spectrophotometry were compared. Results suggested the ultraviolet spectrophotometry was the idealest method with simplicity, utility, and stability, and titration analysis of AgNO3 was next to it. AITC content of pungent products was determined by ultraviolet spectrophotometry, and compared with sensory evaluation. Results suggested that AITC content of pungent products was positively corelated to score of sensory evaluation of pungent degree.AITC had a wide-spectrum antimicrobial activity proved by determination of inhibitory rate. At the same content of AITC, the sequence of the inhibitory effect to microbes was: Paecilomyces variot > Saccharomy cerevisiae > Escherichia coil > Bacillus subtilisi. For a specific microbe, inhibitory rate increased while AITC was added. Inhibitory effect had little fluctuation in a wide range (pH 4.5-7). The inhibitory effect of AITC was antagonistic to alcohol. Inhibitory rate of AITC were higher than that of the same concentration of potassium sorbate, benozate sodium, propanic acid, Nisin, or NaHSO3, and could be enhanced significantly together with potassium sorbate. AITC from plant materials had more antimicrobial activitity than its standard sample.In the study of antimicrobial effect of AITC to 'Chongcai', in order to have maximum AITC content, the optimized processes were as follows: the vegetables were blanched at 90℃ for 2s-4s. Then 3% of salt, 0.05% of vitamine C, and 0.1% of potassium sorbate etc. were added during mixing the blanched vegetable with other condiments. Developing the flavor of pungency at 25℃ were applied for 5h-10h after vacuum packaging. Finally the packages were pasteurized at 90℃ for 10 min and stored at0℃. Based on these processes, research suggested the antimicrobial effect had been in a dose dependent with quantitity of AITC added in 'Chongcai'. For the same perservative effect, 0.01% AITC added to 'Chongcai' might alleviate the sterilization degree, and minimize around 0.05% potassium sorbate. At the maximum usage of 0.1% of potassium sorbate , 0.01% AITC could effectively prolong the shelf life of 'Chongcai'. All in all, AITC is a natural preservative with high application value.
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