Issue link: http://winesandvines.uberflip.com/i/670981
May 2016 WINES&VINES 37 PRACTICAL WINERY & VINEYARD WINEMAKING In general, a winemaker should target a maximum of 1.0 mg/L of TPO at bottling, but this can be difficult to achieve. Levels above 2.5 mg/L can be problematic with a consider- able effect on wine shelf life and sensory profile. Nomacorc's research team revealed that the aroma of Chardonnay wines is altered four months after bottling when wines are exposed to more than 2.5 mg/L of TPO. 12 The decrease of the fruity aromas in Chardonnay wines was associated with an increase in oxi- dation, caramel and honey characters. The ultimate goal of managing TPO during bottling is to reduce bottle-to-bottle variation and provide the same tasting experience for the wine consumer. While most oxygen-manage- ment studies have focused on wine aroma and sulfur dioxide consumption, it is obvious that we are lacking information about how the TPO is affected by bottling practices. Several points need to be addressed as to when the most oxy- gen is dissolved into a wine during bottling as well as how this could be prevented. To examine the bottling processes that have an impact on TPO, California State University, Fresno, embarked on a collaborative study with Nomacorc. Bottling audits Oxygen has the potential to dissolve into wine at every stage of the bottling process. Different cellar practices can have different impacts on TPO. In order to analyze the possible sources of oxygen intake, bottling audits were conducted at 17 California wineries ranging in production capacity from less than 5,000 gallons per year to approximately 120,000 gallons per year. Eight white wines and nine red wines were ana- lyzed for oxygen uptake during bottling using different closure types: eight lots closed with natural cork, five lots closed with Nomacorc synthetic closures, four lots received screwcaps and one lot received agglomerated cork. Total package variations were studied based on the following critical cellar practices with impact on oxygen ingress: • Type of wine • Type of closure and bottle used • Bottling tank volume and diameter • Length and diameter of hose between bottling tank and filler bowl • Number of filling spouts and closure heads • Bottled volume and line speed • Technology of filling • Use of wine to prime the circuit and volume used • Use of inert gas before the process to maintain inert headspace in the bottling tank, inline, to inert bottles before and after filling, at corking, for purging of caps (yes/no and type), and at the end of a bottling run • Use of vacuum (and level of vacuum in negative millibar) at corking TPO VARIATION MID-BOTTLING PROCESS 4 3.5 3 2.5 2 1.5 1 0.5 0 Oxygen concentration (mg/L) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Winery Number n HSO n DO TPO: 0.6 - 3.3 ppm DO: 0.2 - 1.6 ppm HSO: 0.3 - 2.3 ppm TPO is mostly driven by HSO Total package oxygen (TPO), head space oxygen (HSO) and dissolved oxygen (DO) values identified among the 18 audits ranged between 0.6 and 3.3 mg/L. CELLAR PRACTICES AND TPO Audit 11 (TPO<1mg/L) Audit 2 (TPO>3mg/L) General features Wine type Red White Bottled volume (gallons) 19,325 6,500 Bottling speed (bottles/minute) 176 135 Hose length (meters) 24.5 103 Closure type Natural cork Screwcap Number of filling spouts 54 36 Number of corking/capping heads 9 6 Methods for DO management during transfer Use of inert gas to maintain inert headspace in bottling tank N 2 No Use of wine to prime the circuit 25 gallons 50 gallons Use of inert gas before bottling run N 2 N 2 Use of inert gas at end of the bottling run N 2 No Methods for DO management during filling Use of inert gas to purge the bottle N 2 N 2 Technology of filling Vacuum Vacuum Methods for HSO management after filling Use of inert gas after filling N 2 N 2 Use vacuum at corking -102 millibar - Inert gas sparging under screwcap - N 2 The lowest total package oxygen (TPO) level among the 18 audits was recorded during Audit 11, which had a TPO level of 0.6 mg/L. Audit 2 had the highest TPO level of 3.3 mg/L. Information about the equipment used and management procedures are detailed in the above table.