Issue link: http://winesandvines.uberflip.com/i/670981
42 WINES&VINES May 2016 WINEMAKING PRACTICAL WINERY & VINEYARD Total removal of air by purg- ing inert gas is often difficult be- cause the incoming gas causes significant turbulence and mixing as it enters the bottle. Alternately, inert gas can be applied after fill- ing to displace air from the bot- t l e n e c k . T h e m o s t e f f e c t i v e results are usually achieved by combining these two methods. It is important to optimize bottling conditions for each clo- sure type and adapt the final headspace pressure to the speci- fications of each closure/bottle combination. In particular, the limits of using inert gas with a screwcap compared to other closure types are highlighted in this study. The effect of screw- capping on oxygen introduced is more important than with other closure types (see "Clo- sure Effect on HSO at Bottling" on page 40). The importance of managing headspace level for screwcaps has been emphasized in scientific literature. If screwcaps are not appropriately purged with gas- eous N 2 , they will compress a higher level of O 2 under the cap. E. Dimkou et al. reported the impact of managing HSO for screwcaps on the decline of free SO 2 and showed that as lower headspace volume is linked to a screwcap, it is generally associ- ated with higher concentrations of hydrogen sulfide. 17 When closing bottles with s c r e w c a p s , a p p l y i n g a t h i r d dose of inert gas immediately prior to capping can be effec- tive. However, some gas inter- change can occur between the gas inside the empty cap and that in the headspace during the application. Empty screwcaps can be purged, but headspace purging is not anywhere close to 100% effective. Other disadvantages of flush- ing inert gas prior to capping or corking are that this procedure tends to remove some of the de- s i r a b l e v o l a t i l e a r o m a c o m- p o u n d s i m p o r t a n t t o w i n e quality. For this reason, "dosing" of liquid nitrogen on top of the wine in the bottle is favored by some winemakers. Because liquid nitrogen is a cryogenic liquid (-320° F), it is usually delivered to the bottling line through a vacuum-jacketed pipe to minimize premature va- porization of the liquid. When the liquid nitrogen is introduced into the container, the liquid vaporizes due to a temperature change. The liquid nitrogen in- jection drives out oxygen and covers the contents in the con- tainer with nitrogen gas. Application of a drop of liq- uid N 2 is efficient because the gas is induced by evaporation, which allows the gas to be ex- pelled from the bottleneck with- out creating turbulence or air mixing. According to liquid ni- trogen suppliers, by introducing a very small dose of liquid nitro- gen into the bottle after filling, winemakers reduce HSO content by more than 85%. One part of liquid nitrogen warms and turns into 700 parts of gas, displacing oxygen from the headspace. Improper application of a liq- uid N 2 drop or insufficient amount during screwcapping could be associated with an increase of HSO. Because the vapor requires more volume than the liquid it replaces, the pressure within the container is increased. Applying a screwcap while liquid N 2 remains in the head- space could pressurize the head- space and compromise the seal. The liquid N 2 should be allowed to fully evaporate before the cap is applied. The time between d o s i n g o f t h e l i q u i d N 2 a n d screwcapping needs to be de- signed to allow the intended liquid N 2 to gas off. Another option would be that the screwcap is applied but not immediately spun onto the bot- tle. In this case, it is important that the liquid N 2 is allowed to fully evaporate before the cap is sealed to avoid pressure buildup in the bottle. Pressure-influencing factors include the wine level in the bottle, wine temperature and dose-droplet size. Sophisticated liquid nitrogen injectors use electronic controls to adjust in- jector dosing to account for line- speed variations. Various nozzle sizes are available to control the droplet liquid volume at various dose durations. CHART Industries' engineers have designed automated dosing equipment and complete systems that precisely dispense a mea- sured dose of liquid nitrogen into each bottle prior to sealing. Improper application can also be responsible for damaged screw- caps, which affect the efficiency of the inerting step and increase oxy- gen ingress during storage. Proper screwcap application needs to be verified using good quality-assur- ance practices. Pressure effect An important consideration is that leakage, oxidation and wine spoilage can result from exces- sive gas pressure under the clo- sure. As the wine temperature rises, risks of pressure leak prob- lems increase due to wine ex- pansion. A wine volume increase of 0.166 mL per degree Fahren- heit could be registered. 18 As the wine volume changes, the pres- sure rises and the gas in the headspace is compressed. W i t h a n a p p r o p r i a t e f i l l height and adequate vacuum level to compensate for tempera- ture differences, it is possible to maintain internal bottle pressure at levels equivalent or less than 0.1 bar (2 psi) at 68º F. Cork manufacturers suggest to fill to the level designated by CHOOSE THE SPECIALIST Interchangeable modules with or without cart NO CONSTRAINTS LABELING MACHINE. PH. 513-771-7374 MAIL: info@pe-us.com WEB: www.pe-us.com When liquid nitrogen is introduced into the container, the liquid vaporizes due to a temperature change. The liquid nitrogen injection drives out oxygen and covers the contents in the container with nitrogen gas.