| In this study, to provide theoretical clues to the development and production of jujubevinegar, Qingjian Muzao was used as the raw material and the fermentation processes with theliquid and semi-liquid-solid-state fermentation methods were both investigated. The impact ofthe different fermentation methods and the aging methods on the main component, theantioxidant activity and the aroma components in the fermentation process and the agingprocess was also studied. The results are as follows:1.The jujube vinegar fermentation processThe optimal technical parameters of the liquid fermentation method were: the solublesolids content of raw juice17%, the fermentation temperature31°C, the yeast inoculationamount0.82%and the fermentation time43h in the alcoholic fermentation stage; the initialalcohol degree7%, the acetic acid bacteria inoculation amount0.04%, the fermentationtemperature30°C and the fermentation time144h in the acetic acid fermentation stage.The optimal technical parameters of the semi-liquid-solid-state fermentation methodwere: the soluble solid content of raw juice20%, the fermentation temperature31°C, the yeastinoculation amount0.75%and the fermentation time60h in the alcoholic fermentation stage;the ratio of the wheat bran and the jujube wine amazake4/10, the initial alcohol degree7%,the acetic acid bacteria inoculation amount0.05%, the fermentation temperature32°C andthe fermentation time10d in the acetic acid fermentation stage.2.The change of the main components content and antioxidant activities.The total sugar and the reducing sugars significantly decreased (p<0.01); the total phenoland flavonoids increased first and then decreased while the vitamin C was declining duringfermentation process. The original jujube juice, the jujube amazake and the jujube vinegar allshowed very high antioxidant activities. The ABTS+·and·OH scavenging rate of originaljujube juice was significantly higher (p<0.01) than that of the jujube amazake and the jujubevinegar. The DPPH· scavenging rate of the jujube amazake was significantly higher than thatof the original jujube juice and the jujube vinegar. The total reducing ability of the jujubevinegar was significantly (p<0.01) higher than that of the original jujube juice and the jujubeamazake.The main components content and antioxidant activities of the semi-liquid-solid-state fermentation jujube vinegar were significantly higher (p<0.01) than that of liquidfermentation jujube vinegar. In the aging process, the change of total phenols, reducing sugar,total sugar, total acidity and soluble solids content was not significant and had a same trend;the VC content of jujube vinegars using two fermentation methods both decreased, but thechange of liquid fermentation jujube vinegar was slow while the change of thesemi-liquid-solid fermentation jujube vinegar showed a sharp decline in the first five monthsand then leveled to a stable constant value; the flavonoid content of liquid fermentation jujubevinegar decreased, but that of the semi-liquid-solid-state fermentation jujube vinegargradually increased; the DPPH· scavenging rate of the liquid state fermentation jujube vinegardecreased, but that of the semi-liquid-solid-state fermentation jujube vinegar leveled to astable constant value; the ABTS+· scavenging rate of jujube vinegars using two fermentationmethods increased first and then decreased and the change was significant; the·OHscavenging rate of jujube vinegars using two fermentation methods both increased, but theirtotal reducing ability decreased first and then decreased, finally leveled to a stable constantvalue.The main components content and antioxidant activities during aging from light, aging inlight and aging in low-temperature showed a same change trend. The different aging methodshad some effect on the main components and antioxidant activities. The total phenols,flavonoids, VC and reducing sugar content of jujube vinegar during aging in light was lowerthan that of jujube vinegars aging from light and aging in low-temperature, but its total sugarcontent was higher; the soluble solids and total acidities of jujube vinegars by the three agingmethods had not significant difference. The main components content of jujube vinegarsaging from light and aging in low-temperature had not significant difference. The jujubevinegar during aging low-temperature showed higher·OH/DPPH· scavenging rates and totalreducing abilities of than jujube vinegar during aging aging from light and aging in light.3.The change of aroma componentsThe56,56and54kinds of aroma components of the the initial jujube juice, jujube winemash and jujube vinegar were identified, acounting for94.57%,97.37%and98.86%of thetotal aroma, respectively. In the fermentation process, the acids and esters content increasedwhile the alcohols and aldehydes content decreased. The synergy of these aroma componentsgiven the initial jujube juice, jujube wine amazake and jujube vinegar unique flavor.In the aging process, the acids of the jujube vinegar using the liquid fermentationsemi-liquid-solid-state fermentation methods content decreased, but the content of esters andaldehydes content increased; the hydrocarbons, ketones and furans pyrazine content ofsemi-liquid-solid-state fermentation jujube vinegar was higher than that of the liquid fermentation jujube vinegar. A significant increase of aroma components kinds of the jujubevinegar using the liquid fermentation and the semi-liquid-solid-state fermentation methodswas also observed.In the aging process, the aroma components content of jujube vinegars during agingfrom light, aging in light and aging in low-temperature showed a same change trend. However,the esters and alcohols content of jujube vinegar during aging in low-temperature was higherthan that of jujube vinegars during aging from light, aging in light while the aldehydes contentwas significantly lower. The acids content of jujube vinegar during aging from light washigher than that of jujube vinegars during aging in low-temperature and aging in light. Thedifferences of aroma components content and kinds were observed among jujube vinegars bydifferent aging methods which formed different qualities and flavors of jujube vinegars. |
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