Study on Glucosidases Didtribution in Grape-Vine (Chardonnay) Berries
|School||Northwest University of Science and Technology|
|Keywords||Chardonnay β-Glucosidases activity aroma precursor|
β-Glucosidases is one of the key enzymes, which plays an important role in hydrolysising flavour precursors from grape juices or wines. The paper studied the methods on the examination ofβ-Glucosidases activity from Chardonnay berries, optimizing conditions of the enzyme extracting and activity analysis, furthermore testingβ-Glucosidases activity distributing in different parts of Chardonnay berries including berry skins, grape juice, fruit stalk and grape seed. This will establish theorietical foundation for further research on extractingβ-Glucosidases from grape and the wine aroma research in future,and give the suggestions to the winemaking to rich the wine aroma.The main results were showed as follows:1. Crudeβ-Glucosidases extract from Chardonnay berriesIn this paper, the Crudeβ-Glucosidases activity preparation from Chardonnay berries was be studied.Compared immersing Chardonnay berries in ice with in liquid nitrogen.It was found that the best crudeβ-Glucosidases preparation methods was immersed in liquid nitrogen and ground the presence of liquid nitrogen, and that was used in the studies. Theβ-Glucosidases activity was not detected or inexactly detected when Crudeβ-Glucosidases preparation was immersed in ice.2. Optimization of conditions ofβ-Glucosidases activity analysisThrough comparation among electrochemical process, photoluminescence method , spectrophotometric method etc, using p-nitrophanylβ-D-Glucopyranoside (p-NPG) as enzyme substrate, the conditions ofβ-Glucosidases activity analysis in Chardonnay berries were studied. The results indicated that the amount of polyvinypolypyrrolidone (PVP ) had great impact onβ-Glucosidases activity when the enzyme was extracted.With the amount of PVP inceasing from 0 to 4 %, the enzyme activity had the trend to ascend. It attained the apex then the amount of PVP was equal to 4%, and 3 % was choosed in the study.while theβ-Glucosidases reacting liquid is becoming turbidity. The results also showed thatβ-Glucosidases activity was effected by different buffers and pH values. As pH value rose to 6.0, the value ofβ-Glucosidases activity was at its maximum, and then decreased. Under the same pH value conditions enzyme activity was the highest with citric acid-sodium acid phosphate buffer, PNP analysis revealed that the highest asorbance value could be observed when testing wavelength was between 400 nm and 410nm. 405nm was choosed in the trial. It was found that the enzymatic reaction was stable at 37℃within 120 min. The optimum conditions of testingβ-Glucosidases of Chardonnaye berries were investigated by orthogonal design. The results was that, the extracting conditions ofβ-Glucosidases were 3 % concentration of PVP along with the citric acid-sodium acid phosphate buffer as extracting buffer andβ-Glucosidases reacting buffer. The enzymatic reaction should be performed at 37℃within 90 min and the testing wavelength ought to be 405 nm. 3.β-Glucosidases activity distributing in Chardonnay berriesUsing p-nitrophanylβ-D-Glucopyranoside(p-NPG) as enzyme substrate, the conditions were followed as mentioned above.β-Glucosidases activity in different parts of Chardonnay berries were detected.β-Glucosidases activity distributing in Chardonnay berries were that, grape seed> berry skin> grape juice> fruit stalk. Compared to other parts of Chardonnay berries, theβ-Glucosidases activity distributing grape seed was the highest.. It’s different parts of Chardonnay berries was remarkable. The 99 % Confidence Interval ofβ-Glucosidases activity distributing Chardonnay berry skin was 9.2476(U/gFW)±0.5072, The 99 % Confidence Interval ofβ-Glucosidases activity distributing Chardonnay grape juice was 8.6586(U/gFW)±1.3703, The 99 % Confidence Interval ofβ-Glucosidases activity distributing Chardonnay fruit stalk was 2.6035(U/gFW)±0.3489, The 99 % Confidence Interval ofβ-Glucosidases activity distributing Chardonnay grape seed was 10.6682(U/gFW)±0.3871.