Effects Of β-Glucosidase From Aspergillus Niger On Flavoring Regulation And Flavor Compounds Of Wine

Wine flavor is an important indicator of the quality of the wine. β-Glucosidase, as one of the key enzymes improving the wine flavor, can hydrolyze the flavor precursors and then release the volatile aroma components. Currently, the domestic β-glucosidase used in winebrewing basiclly depends on the commercial enzyme abroad because a perfectly suitable β-glucosidase for winebrewing is rare at home, which has hampered the enhancement and improvement of wine flavor. Therefore, it is urgent to screen a β-glucosidase which can not only characterize our unique winebrewing, but give us an independent intellectual property right.In order to provide a theoretical support and practical guidance for the industrial application, based on a screened Aspergillus niger with high β-glucosidase activity previously, this research studied the effect of β-glucosidase on aroma from original wine, the characteristics of precursors from bound aroma and the best conditions for regulation and control of flavor enhancement. Meanwhile, the effect of β-glucosidase on wine color and flavonoid aglycones were also observed to investigate the characteristics of β-glucosidase more comprehensively. To sum it up, the main results are as following:(1) Crude enzyme solution of A. niger fermented in liquid medium was filtration centrifugation,(NH4)2SO4 precipitation, QFF ion-exchange chromatography, gel filtration chromatography,then the electrophoresis pure level β-glucosidase was acquired. All in all, the purified β-glucosidase had met the standards of subsequent enzymatic hydrolysis.(2) The aroma potential of fresh Vitis vinifera wine and aroma characteristics of different sources of β-glucosidase to bound glycoside was analyzed using SPME-GC-MS. Four kinds of different sources of glucosidase have significant effects on bound form precursors. A total of 84 kinds of flavors from four categories were detected. 73 kinds of flavors in 84 detected above had significant differences. Compared with three kinds of commercial enzyme, the content and specie of terpenes in experiment enzyme were the most. Therefore, β-glucosidase exhibited an excellent ability to hydrolyze the flavor precursors and release the aroma components, especially for the bound terpenes. The analysis of PCA showed that different sources of glucosidase enzymes had different aroma characteristics. Among them, SIHA enzyme had an obvious influence on nerolidol, geraniol and so on; Sigma enzyme’s effect on β-damascone was obvious; experimental enzyme for 4-terpenols, α-terpineol, linalool and other terpenes effect were remarkable.(3) The effect of β-glucosidase from A. niger on flavor regulation and aroma compounds of Cabernet Sauvignon was analyzed using L9(34) with Kramer sensory evaluation and SPME-GC-MS. The optimized hydrolysis parameters were under the temperature of 45℃ for 4.0 h with enzyme dosage of 4.0 U·m L﹣1. A total of 59 aroma compounds were detected and 35 components showed significant differences after treatment. The total relative content of compounds increased 24.59%. The most obvious changes appeared in C13-norisoprenoids and terpenes incremental, which increased of 118.54%. Enzymatic treatment had positive effects on typical aroma improvement and flavor enhancement in wine.(4) To study the role and impact of β-glucosidase on wine color, monomer anthocyanins before and after enzymatic treatment were qualitatively and quantitatively analyzed using HPLC with with CIELab color space parameters. The CIELab results indicated that afte the hydrolysis, a* value of red decreased of 28.1%, in contrast, b* value of yellow increased of 31.4%. In addition, L* and h values of brightness and color respectively increased, in contrast, C* value decreased. Moreover, the color of enzymatic sample became shallow, and its saturation also decreased compared with the non-enzymatic sample. The HPLC results demonstated that seven kinds of anthocyanins monomers reduced after hydrolysis, and the total anthocyanin content decreased of 69.9%. Therefore, β-glucosidase enzyme have a serious impact on the color of red wine.(5) To study the role and effects of β-glucosidase on flavonoid aglycone substances, a qualitative and quantitative detection of trace flavonoid aglycone substances in Cabernet Sauvignon using UPLC-MS/MS showed that the content of flavonoids detected increased after enzymatic treatment. Here, quercetin increased the most, about 2.33 times. Secondly, myricetin had an increase of 63.85%. In addition, morin was first dected after enzymatic treatment. Therefore, β-glucosidase not only increased the content of flavonoids but also enriched the species, and it also plays a positive role on the antioxidant function of wine.