Issue link: http://winesandvines.uberflip.com/i/742839
110 WINES&VINES November 2016 WINEMAKING WINE EAST take is less when large volumes of wine are used in comparison to smaller volumes. Studies have found that the beginning and end of a bottling run add higher DO levels. These increases are caused by the filtration system, dead vol- ume, oxygen content near the wine surface and turbulence in the final bottles. The guideline for maximum dissolved oxygen in the bottle has been established at 1.0 ppm. To achieve this level, winemakers must employ several measures to lessen the exposure of wines to air—the source of most oxygen exposure. First, all cooperage must be filled to capacity or cov- ered with inert gas such as nitro- gen, carbon dioxide or argon, and hoses must be as short as possible with tight coupling links. The holding tank for the wine prior to bottling needs special at- tention, such as establishing a desirable wine temperature, using inert gas in wine transfer, avoiding turbulence and stirring without inert gas. Wine bottling is particularly important in con- trolling oxygen enrichment. Wine turbulence should be kept at a minimum and filling levels main- tained at certain guidelines. Also, bottles need to be flushed with nitrogen (usually two to three bottle volumes) and a vacuum provided during filling. In conclu- sion, wines before bottling should contain less than 0.5 ppm DO. The DO level in bottled wine is extremely important. However, headspace oxygen (HSO) that is contained in the volume from the top of the wine to the bottom of the closure also is critical to the DO level. The HSO is an addi- tional source and moves gradually into the wine. The amount of oxy- gen in the headspace volume de- p e n d s o n t h e c l o s u r e t y p e : cylindrical, such as cork or a syn- thetic, or screwcap. A screwcap has the greatest HS (14 ml), while corks vary between 3 ml and 7 ml. Also, the recommended HS height is 15 mm, which avoids cylindrical ejection and leakage after HS gas compression at corking. Excessive pressures often are c a u s e d b y l o w - t e m p e r a t u r e wines, small HS volumes, high storage temperatures and bot- tling without HS sparging and vacuum. Studies have found that HS oxygen may increase the DO as much as 60%. Also, the DO in wine bottles with screwcaps gen- erally experience a DO increase three times greater than cylindri- cal closures. Another aspect that increases DO in bottled wines concerns the passing of internal gas (air) within the cylindrical closure pores to the HS at the sealing process. However, the amount of O 2 escaping to the bottled wine depends on the in- ternal pressure, storage time and bottle orientation during bottle aging. Sources of DO: closure type The third source that affects DO level relates to the closure type used in bottling. The oxygen- transfer rate (OTR) varies widely among closures. Because of this variation, types of closures influ- ence the chemical and sensory properties of bottled wines. For example, research findings have indicated that screwcaps maintain higher levels of free SO 2 and result in less browning compared to natural, synthetic and technical corks in certain white varietal wines. However, screwcaps may offer reduced characters at ex- tended storage periods. In another instance, synthetic closures may bring about oxidized flavor during prolonged storage. Also, performance studies of natu- ral corks have shown variability in OTR, which may lead to sensory differences in wine. Certainly, this response depends on composition and wine precursors. Although wines may be vinif- ied within the guideline levels for DO (<1.0 ppm) and HSO (<2.0 ppm), this does not excuse wine- makers from adding SO 2 . This chemical is unique because it of- fers both antioxidant and antimi- crobial properties. In wine, SO 2 prevents unwelcomed browning and oxidation processes. These responses are due to chemical re- actions that are much slower than enzymatic oxidation. The use of SO 2 and its interac- tion with O 2 is complex, involving several pathways and reactions. The ability of SO 2 to react with Natural Corks Champagne Corks Twinline Corks Bartops VISION Synthetic Corks G-Cap® Screw Caps Sales Representatives: Chris & Liz Stamp info@lakewoodcork.com lakewoodcork.com 4024 State Route 14 Watkins Glen, NY 14891 607-535-9252 607-535-6656 Fax PIONEER INNOVATOR PARTNER Racking can result in oxygen uptake of up to 5 parts per million.