| In this paper, Malolactic fermentation (MLF) in Cabernet Sauvignon dry red wine was studied with commercial strain 31DH as the control, and with three Oenococcus oeni strains including SD-2a, SD-lb and SD-2h selected by College of Enology, Northwest Sci-Tech University of Agriculture and Forestry.By the selection of inoculating conditions, the optimizing pre-culture method for artificial 'inoculation of Oenococcus oeni and feasible inoculating concentration were determined.The results showed that Oenococcus oeni needed domestication and cultivation in imitative wine environment to prevent their excess deaths and postponement of MLF at the time of inoculation. The conditions of domestication and cultivation were ATB medium + dehydrated alcohol (11%, v/v) + S02(10mg/L), pH 3.2, and three days' time, and grape juice medium, lasting cultivating temperature of 20 癈 , and five days' time, respectively.Inoculating concentration Mainly influenced MLF rate and volatile acid. Within the range from three percent to ten percent, with inoculating concentration increasing, rate of MLF accelerated and volatile acid yield reduced. Thus, inoculating concentration of three percent was reasonable parameter.Some items were analyzed in wines after MLF which included MLF rate, rate of degrading malate, volatile acid content, wine anthocyanin, organic acids, tannin, total phenols, flavor balance index and amino acids. Combining above outcomes with the organoleptic quality evaluation of MLF wines, this study determined the Oenococcus oeni strain with better enological characteristics.The results indicated that three strains had many differences in enological characteristics from each other, and they could produce different influences on wine quality. In the same conditions, the MLF rates of SD-2a and SD-lb were faster than that of the control 31DH, while SD-2h was equivalent to the strain 31DH in MLF rate. Moreover, SD-2a and SD-2H had stronger capacities of degrading malic acid, but there were no remarkable differences between strain SD-lb and the control 3 1DH in this aspect.After completing MLF with these malolactic bacteria, pH values and flavor balance indexey of wines increased; malate contents reduced obviously; large numbers' lactic acid produced; color intensities of wines were decreased .to some extent, but changes of total phenols and tannin , were notremarkable. In addition, contents of volatile acids in MLF wines were in the limit of quality standard, and among them, the MLF wine by inoculating SD-2a had stable and less volatile acid occurrence.Conducting MLF with three Oenococcus oeni strains added to the varieties and contents of amino acids in wines. In them, the increments of alanine, valine, glutamic acid, proline, glycin and serine were considerable. In metabolizing argine, there had no obvious difference among three strains and the control 3 1 DH. Thus, three selected strains had better characters of degrading argininc that they couldn't over-degrade arginine to produce large numbers' precursors of carcinogenic ethyl carbamate as citrulline, etc.The organoleptic evaluation showed that the Cabernet Sauvignon dry red wine after MLF by inoculating SD-2a had mild and harmonious1 taste, heavy fragrance, structural balance and higher quality. SD-2h wine had very light color and abnormal odor, while the aroma and the color of MLF wine with SD-lb were lighter compared to the control 31DH wine though its quality had relatively improved contrasted with non-maiolactic fermenting wine.In conclusion from physical and chemical analysis and organoleptic evaluation on MLF wines, Oenococcus oeni SD-2a was a more excellent strain with better enological characteristics,... |
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