Research Of Volatile Components In Pickles During Fermentation

Volatile components in head cabbage pickles of different fermentation ways were extracted during fermentation using method of headspace solid phase micro-extraction (HS-SPME) and analyzed by gas chromatograph-mass spectrometry (GC-MS). The influence of dominant lactic acid bacteria (LAB) on Sichuan pickles were analyzed as well. The main results were summarized as below:(1) For the fermentation process of the pickles fermented by old brine, new brine, Lactobacillus plantarum, Lactobacillus brevis and Leuconostoc mesenteroides, the number of LAB and content of nitrite increased first and then started to drop along with the extension of time. Total acid content increased and content of reducing sugar decreased gradually. In addition, at the forth day of pickle fermented by new brine the peak content of nitrite reached to 25.85 mg/kg while Lactobacillus brevis had a strong ability in degradation of nitrite and the peak content reached to 8.72mg/kg at the second day of fermentation. In general, pickle fermented by old brine had advantages in the respects of acid production rate, ability of nitrite degradation, flavor, taste and quality.(2) A total of 54,45,60,50 and 61 kinds of compounds were were identified in pickle fermented by old brine, pickle of natural fermentation, pickle fermented by Lactobacillus plantarum, pickle fermented by Lactobacillus brevis and pickle fermented by Leuconostoc mesenteroides respectively. The species and relative content of esters were the most in five kinds of pickles. Isothiocyanates were characteristically volatile components of head cabbage pickles.(3) Method of relative odor activity value (ROAV) was used to determine the key odor compounds in different pickles. The results showed that there was great difference in the species of the key odor compounds of different pickles and 1-Nonanal was the only common component of them. The key odor compounds of pickle fermented by old brine were 1-Nonanal, Isoamyl acetate,1-Heptanol, Ethyl caprate, Linalool, Allyl Isothiocyanate, D-Limonene,1-Nonanol,3-Octanol and Phenylethyl Alcohol. The key odor compounds of natural fermentation pickle were 1-Nonanal, Allyl Isothiocyanate, Decanal,2-Undecanone and D-Limonene. The key odor compounds of pickle fermented by Lactobacillus plantarum were Dimethyl trisulfide, Disulfide, dimethyl and 1-Nonanal. The key odor compounds of pickle fermented by Lactobacillus brevis were 1-Nonanal, Ethyl caproate, Linalool, D-Limonene and Phenylacetaldehyde.1-Nonanal, D-Limonene, Allyl isothiocyanate, 1-Nonanol and Leaf alcohol were the key odor compounds of pickle fermented by Leuconostoc mesenteroides.(4) The result of principal component analysis (PCA) indicated that the overall flavor of pickles fermented by old brine, Lactobacillus brevis and Lactobacillus plantarum were obviously different. On the contrary, pickles of natural fermentation and fermented by Leuconostoc mesenteroides were similar in the overall flavor and had a close relationship with Allyl Isothiocyanate and D-Limonene.