| Aronia melanocarpa is rich in active components such as polyphenols and anthocyanins,but its unique strong grassy flavor and sour taste limit the research and development of related products.In this thesis,lactic acid bacteria which show a good fermentability were used to ferment Aronia melanocarpa,one hand,the growth and metabolism of lactic acid bacteria can improve the flavor and texture of Aronia,on the other hand,making full use of the extracellular polysaccharides(EPS)produced by the metabolism can enhance active components as well as the nutritional value.This study initially evaluated the optimum process condition of L.plantarum C8-1 for Aronia juice fermentation and then assessed the effect of fermentation on the juice’s physical and chemical indicators,such as total acids,total phenols,soluble solids,organic acids and volatile substances,etc.Moreover,the EPS produced by the metabolism of L.plantarum C8-1 were separated and purified with a preliminary study on primary structure.Finally,the fermented juice’s quality change was detected during storage time.The main results of this study are as follows:1.Acid environment(low pH level)of Aronia juice is suitable for reproduction of L.plantarum C8-1.Inoculation amount and material-liquid ratio have significant effect on the fermentation compared with fermentation time,fermentation temperature as well as sucrose content.The results showed the optimum fermentation condition were determined as follows:inoculation amount 91g CFU/mL,fermentation temperature 35℃,fermentation time 22 h and material-liquid ratio 25%.2.SPME-GC-MS were applied to analyze the volatile components in the Aronia juice before and after fermentation.The results indicated that fermentation can significantly change the variety and conten of alcohols,eaters,phenols,aldehydes,ketones,alkenes,and phenols.Compared with fresh juice which contain 20 volatile substance,10 substance were disappeared and 22 new substance were formed after fermentation.The content of benzaldehyde with bitter almond flavor decreased by 36.77%,and a large number of pleasure odor substances such as ethylester,1-Dodecanol,and Dodecanal were produced.3.The content of total acid,total phenol and organic acid in the fermented juice were significantly increased.The HPLC analysis results regarding the variety and content of organic acid were showed that after fermentation the content of malic acid decreased by 35.42%which is followed with a rise by 60.69%and 22.71%in the content of lactic acid and the total content of organic acids respectively.Moreover,changes in the variety and content of organic acids have encouraging effect on the improvement of the flavor of the Aronia juice.4.An acidic EPS of L.plantarum C8-1 was separated and purified by gradient elution.Results of FT-IR and NMR showed that suger ring structure of EPS was pyranose ring,and the configuration of glycosidic bonds was a-glycosidic bond.5.After stored at 4℃ for 30 days,the number of L.plantarum C8-1 in the fermented juice were 7.81g CFU/mL,and the number of miscellaneous bacteria were 0.71g CFU/mL,which met the requirements of commercial viable lactic acid bacteric beverage products.Compared with fresh juice,it was found that the L.plantarum C8-1 as a dominant straining the fermented juice can inhibit the growth and reproduction of competitors.E-nose and E-tongue can classify the fermented juice of differented juice of different storage periods.The results showed that the longer the storage time was,the highter the similarity of the taste of the fermented juice was. |
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