Optimization Of The Extraction Conditions And Analysis Of The Changes Of Volatile Compounds In The Fermentation Of Traditional Sichuan Pickles

The Sichuan pickles are deeply loved by everyone, for they are fresh and delicious, besides, they have crisp texture, unique flavor and rich nutrition. In this experiment,we put the pickles as the raw materials to study the different extracting effects by different methods and to optimize the method; The differences of volatile components and relative odor activity of the pickles put as the different raw materials were researched. On the contrast of natural fermentation, the dynamic changes of physical and chemical index and volatile components of the traditional fermented mustard were researched.The main results and conclusions are as follows:1. Traditional simultaneous distillation extraction (SDE) and head space solid phase microextraction (HS-SPME) were compared for their extracting effect in the volatile compounds of Sichuan traditional pickled radish.It was found that the repeatability of SDE method was higher than HS-SPME method.But isothiocyanates and sulfocompounds which had an important role in aroma of pickles reported in literature were better extracted by HS-SPME method. The results indicated that SDE method provided better extracting effects for volatile compounds with higher molecular mass and boiling point, especially for saturated alkane, but saturated alkanes which reported in the literature contributed little to the flavor. Therefore, the HS-SPME method on analysis the volatile components of pickles was superior to SDE method. Comparing the extracting effects of five extraction fibers, it was found that no matter analysis of the number or total peak area,65μmDVB/PDMS extraction fiber was better than the other four fibers, based on the analysis of pickles radish in the volatile components.So DVB/PDMS fiber was the most suitable for extracting volatile compounds of Sichuan traditional pickles.2.The volatile components of Sichuan traditional fermented radish were absorbed by HS-SPME and analyzed by GC-MS. The extraction conditions were investigated by using single factor and response surface methodology based on Box-Benhnken centre design principles. The extraction temperature, extraction time and sample volume were used as affected factors while the total peak area of chromatogram as response value in this study. The results indicated that the optimum conditions for volatile components extraction from Sichuan traditional fermented radish by HS-SPME were obtained as followed:extraction temperature 43.00℃, extraction time 30.50 min and sample volume 5.07g. Under the above conditions,44 different compounds were identified, including hydrocarbons, esters, sulfocompounds, aldehydes,phenols,alcohols and ethers. Among them, Butane,1-isothiocyanato-, Ethane, isothiocyanato-,4-Methylpentyl isothiocyanate, Hexane,1-isothiocyanato-, n-Pentyl isothiocyanate,D-Limonene,Naphthalene,alpha.-Pinene,Dimethyl disulfide, Dimethyl trisulfide and 2-Methoxyphenol were the main compounds.3. Pickles that put as different raw materials were researched using the HS-SPME to extract and GC-MS to analyse.The results showed that this experiment had detected 44 kinds of volatile components in fermented radish, that Butane,1-isothiocyanato-was the main component. From the pickled mustard,24 kinds of volatile components were detected, of which Allyl isothiocyanate was the main component. From the pickled cabbage,21 kinds of volatile compounds were detected, of which the relative content of Allyl isothiocyanate was the highest. From the pickled cucumber,22 kinds of volatile components were detected,of which the relative content of 2,6-Nonadienal,(2E,6E)-was the highest. From the pickled celery,25 kinds of volatile components were detected,of which D-Limonene was the main component.4. Using relative odor activity analysis,the main components of pickles were Allyl isothiocyanate, Dimethyl disulfide, Dimethyl trisulfide, Decanal, Benzeneacetaldehyde,1-Nonanal, (E,E)-2,4-Nonadienal, Hexanal, beta-Ionone, 1-Octen-3-ol, D-Limonene.So that, isothiocyanates, sulfocompounds, aldehydes, ketones, alcohols, alkenes played huge roles in the Sichuan traditional pickles’odor.5.After fermentation, the fresh mustard had produced large amounts of isothiocyanates, aldehydes, alcohols, hydrocarbons, ketones, ethers, nitrogen compounds. But the relative content of esters were inverse. Traditional pickles on the acidity, taste and safety were better than that of natural fermentation. Using the optimization HS-SPME to extract and GC-MS to identify the volatile components of traditional pickled mustard in the fermentation process,49 kinds of volatile components were identified and 48 kinds of volatile components were identified in natural fermentation. During the whole traditional fermentation, isothiocyanates was not significantly changed.Aldehydes, alcohols and hydrocarbons had a trend of declining after rising first. Aldehydes could achieved a higher level at the beginning of fermentation. But,alcohols and hydrocarbons could achieved the highest level in fermentation medium or late.The content of esters and nitrogen compounds increased slightly.Ketone held a downward trend.In the whole processes of natural fermentation, the changing trends of isothiocyanates, aldehydes, alcohols, hydrocarbons were similar to traditional pickles.But the content of aldehydes had increased again in the later, and sulfocompound,Heterocyclic compounds, phenosl and pyrazine appeared in the medium of fermentation.Ketones increased gradually and achieved the highest level in the late fermentation.The content of nitrogen compounds and esters changed little.