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78 WINES&VINES December 2016 WINEMAKING WINE EAST For the five wines in the first category (< 0.5 ppm), the DO level was 0.3 ppm, which in- creased to 1.0 ppm at bottling. All other wines and their respective categories showed the same direct correlation. The recommended maximum DO level (1.0 ppm) at bottling was exceeded for these two categories. Certainly wine temperature, num- ber of bottling stops and wine level in the hold- ing tank with inert gas protection are issues that need to be addressed to control wine oxy- gen levels at this critical stage. The oxygen amounts in wines are highly dependent on temperature, and wines at lower temperatures contain more oxygen than at higher temperatures. The recommended wine temperature at bottling is between 60º and 70º F, but only six wines out of 14 were within these limits. In this study, wine tem- peratures were quite variable, ranging from 54º to 72º F. Of course, some temperature changes will occur from the holding tank to the bottled wine. Keep in mind that several important issues are influenced by tempera- tures, including fill height at bottling, head- space volume and headspace pressure. After obtaining a responsible amount of oxy- gen (< 0.5 ppm) in the holding tank, the wine- maker's next concern is controlling O 2 enrichment at bottling. The common wine bottle contains 750ml of air and exceeds 200 mg of oxygen. This presents a problem for the wine- maker, because bottling involves turbulence and pumping conditions that lead to high DO values when not managed correctly. To minimize the O 2 impact, an inert gas needs to be used in transferring wine and covering unfilled tanks, flushing and also using a vacuum prior to filling. Of course, the wine must be in the right condi- tion, with proper FSO 2 content, temperature and DO content at less than 0.5 ppm. Results showed that 85% of the wines at bot- tling were above the industry guideline of 1.0 ppm for dissolved oxygen (see table on page 76). The analyses for DO levels are summarized in the figure "Average Concentration of DO in Wines at Bottling" on page 79. These data illustrate the DO variability among the wines at bottling (zero days storage). Just two wineries produced wines that were below the recommended DO value of <1.0 ppm. However, seven wines were slightly above the guideline, ranging from 1.1 to 1.5 ppm, while five wines were not satisfactory. The evolution of DO for the storage intervals (zero to 126 days) is shown in the table above, "Average Concentration of Dissolved Oxygen, Headspace Oxygen and Total Package Oxygen." The majority of the measurements indicated a rapid decrease by seven days, and most were consumed by 63 days. The rate of decrease was illustrated among the results. A higher DO level at bottling (zero days) took longer to be com- pletely consumed, meaning more time for chemi- cal reactions to occur. A real pattern was found concerning bottle evacuation effects on the DO content in bottled wines. Some important points can be observed in evaluating the DO results (averages) of wines from two filling operations, with and without inert gas and/or vacuum evacuation. For each bottling operation, automation and gravity, bottle evacuation was critical in reduc- ing DO contents. Although gravity filling with- out evacuation led to undesirable DO levels in six wines with an average of 2.2 ppm, two gravity-filled wines under evacuation were near the DO guideline, <1.0 ppm. Surprisingly, these wines contained less DO than the five wines from the automated bottling operations that were evacuated with inert gas and/or vacuum expressing an average of 1.4 ppm. One wine that was automated in bottling without evacuation expressed a rather high level of 3.7 ppm DO in the bottled wine. However, this wine also contained a high level of DO at the bottling tank of 2.2 ppm. Headspace oxygen Although the importance of DO content in wine at bottling is obvious, the second factor, head- space, is considered the main source of oxygen pickup in bottled wine. This factor is often overlooked or ignored by many winemakers. Wine comes into contact with headspace gas at bottling and sealing, and oxygen dissolves into the wine. Different closure types have an effect on headspace volume and therefore im- pact oxygen content in the bottled wine. For example, screwcapped bottles may have three times the headspace volume as bottles finished with cylindrical closures (corks). As mentioned earlier, the use of vacuum and flushing with inert gases (CO 2 or N 2 ) is often employed to minimize HSO. The recommended level for HSO is 2.0 ppm to resist oxidation. The headspace oxygen levels at bottling were variable and ranged from 0.6 to 4.9 ppm (see "Average Concentration of HSO in Each Wine" on page 77). More than 65% of the wines exceeded the HSO guideline (2.0 ppm) for controlling oxidation and preserving sen- sory properties. The most striking observation was the extremely high HSO values for six wines (3.7 to 4.9 ppm). Another interesting finding was the HSO measurements within the suggested guideline. Six wines were found in this category, and three of these wines were AVERAGE CONCENTRATION OF DISSOLVED OXYGEN, HEADSPACE OXYGEN AND TOTAL PACKAGE OXYGEN Winery Average DO (ppm) Average HSO (ppm) TPO (ppm) Storage Days 0 7 21 63 126 0 7 21 63 126 0 7 21 63 126 A 1.4 0.5 0.2 0.1 0.0 0.7 1.0 1.0 0.5 0.3 2.1 1.6 1.1 0.6 0.3 B 2.1 1.5 1.0 0.1 0.0 1.0 0.8 0.4 0.1 0.0 3.1 2.3 1.4 0.1 0.1 C 1.4 0.8 0.5 0.2 0.0 2.1 1.8 1.3 0.6 0.2 3.5 2.6 1.8 0.7 0.3 D 3.9 1.5 0.0 0.0 0.0 1.4 1.0 0.8 0.3 0.1 5.3 2.5 0.8 0.3 0.1 E 1.1 0.2 0.0 0.1 0.0 1.4 1.0 0.7 0.2 0.1 2.5 1.2 0.7 0.2 0.1 F 1.4 0.2 0.2 0.0 0.0 1.6 1.0 0.5 0.1 0.0 3.0 1.2 0.6 0.1 0.1 G 3.3 0.6 0.5 0.4 0.0 4.9 4.0 3.4 2.3 2.6 8.0 4.6 3.9 2.7 2.6 H 2.5 4.4 3.9 1.1 0.0 4.5 1.9 1.0 0.3 0.0 7.0 6.2 4.8 1.5 0.1 I 0.7 0.1 0.0 0.0 0.0 3.9 1.5 0.4 0.1 0.0 4.6 1.6 0.5 0.1 0.0 J 1.3 0.7 0.7 0.1 0.1 4.2 2.8 1.6 0.2 0.0 5.5 3.5 2.3 0.3 0.1 K 0.5 0.2 0.2 0.1 0.1 0.6 0.2 0.2 0.1 0.1 1.1 1.6 0.5 0.1 0.0 L 1.5 0.4 0.0 0.0 0.0 4.3 3.9 3.3 1.6 0.5 5.8 3.9 3.3 1.6 0.5 M 1.3 0.3 0.2 0.0 0.0 2.4 1.6 0.5 0.3 0.2 3.7 1.9 0.7 0.3 0.2 N 3.7 1.7 1.5 0.0 0.0 3.2 3.0 1.4 0.8 0.2 6.9 4.7 2.8 0.8 0.2 The majority of measurements indicated a rapid increase in dissolved oxygen (DO) by seven days, and most were consumed by 63 days.