Study On Change Of Flavor Components In Microorganism Fermentation Process Of Pakchoi

Pakchoi(Brassica campestris L.ssp.Chinesis L.)is known as non-knot pakchoi,rapeseed and cabbage.Each species have two types,includig ordinary pakchoi and purple pakchoi.Pakchoi is one of brassica plant,belongs to the family of brassicacea.Pakchoi contains rich nutrients,which includes vitamin C,soluble sugar,glucosinolates and other functional substances.Purple pakchoi is very rich in anthocyanins,possess various physiological activities.Vegetable fermentation is based on fresh vegetables as raw materials.In order to change the processing methods of vegetable properties,beneficial microorganisms are utilized and their growth conditions are controlled.Vegetable fermentation can not only prolong the storage period of vegetables,but also has fresh,sweet,crisp,tender,salty,spicy and other unique fragrances,There are many kinds of fermented vegetables on the market such as sichuan pickles,northeast sauerkraut,fuling zhacai,etc.However,there are few studies on the changes of anthocyanins of purple pakchoi after fermentation.In this study,6 kinds of pakchoi(Zi Guan-ZG,Zi Song-ZS,Zi Luolan-ZLL,Zi Jinxing-ZJX,You Dong-YD,Wu Yueman-WYM)were fermented by lactic acid bacteria fermentation and the changes of flavor components in pakchoi before and after fermentation were studied.The best fermentation conditions were screened out,volatile flavor components,anthocyanins,vitamin C and carbohydrates were detected,sensory evaluation and nitrite detection of fermented pakchoi were carried out.The changes of flavor components of pakchoi before and after fermentation were identified,which provided theoretical support and technical reference for the research and utilization of microbial fermentation of pakchoi.The main research contents are as follows:Through orthogonal experiment,the effects of flavor components of pakchoi by different fermentation conditions(salt concentration,white sugar concentration,white vinegar concentration,liquor concentration)was studied.Combining the results of volatile flavor components and sensory evaluation,the second group(salt concentration 6%,sugar concentration 4%,white vinegar concentration 3.5%,liquor concentration 1.5%)was determined to be the best fermentation conditions among the 9 groups.The volatile flavor components of 6 kinds of pakchoi before and after fermentation were detected by gas chromatography-mass spectrometry(GC-MS).The results showed that aldehydes,alcohols and esters were the main volatile flavor components.The content and species of volatile flavor components of fermented purple pakchoi(ZG)were higher than those of other 5 fermented pakchois.The content and species of anthocyanins in 4 kinds of purple pakchois before and after fermentation were detected by UPLC-MS.There is a total of 22 anthocyanins were detected.The content of anthocyanin in ZG after fermentation was higher than that of other 3 kinds of purple pakchoi.The contents of vitamin C and sugar in 6 pakchoi before and after fermentation were determined by high performance liquid chromatography(HPLC).The results showed that the contents of vitamin C and carbohydrates in fermented ZG were higher than those in other 5 kinds of fermented pakchoi.6 pakchoi obtained sensory evaluation.The results of sensory evaluation showed that there were significant differences among different kinds of pakchoi.The fermented purple pakchoi was superior to the fermented ordinary pakchoi in sensory sense,and the ZG had the best taste among samples.Nitrite in 6 kinds of fermented pakchoi was detected.The results showed the content of nitrite in 6 kinds of fermented pakchoi was lower than the national standard.