McLaren Vale                   

All Marius wines are now bottled under screw cap.

I find it incredible that the wine industry and the wine consumer have tolerated corks for so long.  

Estimates of spoiled wine from trichloroanisole (TCA) contamination run from 3% to 15%, add to that number (whatever it may be)

the random oxidation from badly sealing corks and then throw in all that unexplained bottle variation.  Good luck in the lottery!

A recent study was carried out by Allen Hart who is the R & D Winemaker for Southcorp, the study has been carried out since 1997

on Penfolds and Seppelt wines.  

An abstract of the report in PDF form may be downloaded here but the conclusion of the study (below) indicates that red wine will 

evolve and develop maturation without the ingress of oxygen so there is no reason why a wine sealed under screw cap will not 

develop like a wine under a perfect cork.

Conclusion

"From this study it is apparent that oxygen was not a vital component for the ongoing evolution and maturation of these red wines after 

bottling. It is clear that access to small but measurable amounts of oxygen (eg synthetic closures, approximately 4 CC O2/bottle/year) 

will accelerate the evolution and maturation of red wine through oxidative reactions. However, red wine will continue to evolve 

without measurable oxygen ingress via a closure, primarily through what is assumed to be anaerobic reactions. 

Some bottled wine may express “reductive” characters in such an anaerobic environment, in contrast to the wine developing oxidised 

characters in a more aerobic environment. Given the low ranking scores for reductive characteristics observed in the Bin 389 

trial wines, the low levels recorded in this instance are not considered to be commercially unacceptable."