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W i n e s & V i n e s D e C e M B e R 2 0 1 4 61 Particularly telling is the comparison of wineries 14 and 15—actually the same winery bottling the same wine with screwcap in the morning (14) and syn- thetic closures in the afternoon (15). Despite the use of liquid nitrogen drip post-filling to inert the headspace of the screwcaps only, we see a huge increase in the TPO due to headspace O 2 . This highly professional configuration is actually the exception. In general screwcap bottlings displayed both high HSO levels and variability. These data do not challenge the widely held belief that when properly applied and spared from physical damage, screw- cap closures (at least the ones based on tin liners) can provide a nearly hermetic seal with a consistent and very low oxy- gen-transmission rate. The tradeoff with today's technology is that they leave a very large headspace that cannot be evac- uated with vacuum. In addition, half mea- sures such as liquid nitrogen drops to minimize HSO may result in very high product variability in sensitive whites. The bottom line 1) Set yourself up for measuring DO pickup in your finishing process prior to bottling. Good auditing equipment is available and expertise is valuable. You can also consider hiring a consultant to help you get your act together by auditing your line, reconfiguring your procedures, selecting measuring equipment and train- ing your team. 2) Eliminate the U-shaped curve by back-gassing your sending tank with a pancake regulator at high flow/low psi. Inert the filler bowl and other sources of oxygen. Recirculate adequate quantities of wine. 3) Inert gas and oxygen are invisible. It's really easy to fool yourself by enacting procedures in name only. Liquid nitrogen drips and other measures may look good on paper, but make sure they work. 4) Measure your wine's oxygen appe- tite, and suit it to the aging trajectory you require and the closure you choose. The study's full findings will be revealed in early 2015. Visit winescienceforum.com for more information. Clark Smith is winemaker for Wine- Smith and founder of the wine technology firm Vinovation. He lectures widely on an ancient yet innovative view of American winemaking. G R A P E G R O W I N G W I N E M A K I N G