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p r a c t i c a l w i n e r y & v i n e ya r d J a n U a r y 2 0 1 5 41 P A C K A G I N G tested closure explains the large diver- gence in composition and sensory prop- opment during post-bottling. 14-21 The different OTR properties of each Although, some of these performances represent an improvement compared to previous results, the synthetic closure OTRs are still much more significant than exhibited by corks and screw-caps. Screw caps also have introduced closures with different oxygen transmission rates based on permeable internal liners. Saran-tin displays a very low OTR (less than 0.5 µL of oxygen/closure/day), saranex is slightly more permeable at 1.0 µL. The observed OTR for natural cork stoppers was quite similar to results in previous studies. At a level of 1.3 µL per day, the OTR was lower than seen with synthetics and higher than seen with screw caps. With cork's primary oxygen pathway observed by diffusion, ongoing OTR is reduced over time. Technical corks (Neutrocork and Twin Top) and cork-based closures such as Diam display a very similar performance, exhibiting a consistent low OTR around 0.5 µL of oxygen per closure per day. Impact of closure OTR on chemical and sensory composition of bottled wines Several closure trials have been con- ducted since 1999 in order to understand how closure selection and their compara- tive OTR will impact wine flavor devel- 0 1 2 4 5 Aroma c intensity, LSD = 0.7 Overall fruit Freshness Oxida on Reduc on Bo le ampoule Natural cork Colmated cork Microagglomerate Synthe c Sc saran- n Sc saranex LSD = 0.8 LSD = 0.7 LSD = 0.6 LSD = 0.6 3 Figure 4: The effect of closure treatment on selected sensory attributes for a Sauvignon Blanc wine after 24 months of storage. The values are the means of five replicates. Least significant differences (LSD) at the 5% level are indicated.