AST. Wonderful product with regards to getting some good protection out in the vineyards, the tractor drivers throw it onto the trailers as soon as the machine offloads. Juice keeps its green colour for very long period due to good protection against oxygen. What I have noticed is how well the ascorbic acid first binds the oxygen then after that the sulphur binds. I gather info from my analyses once the juice arrives in the cellar. I use a drum filter(oxidative) to filter my lees and even then the juice is still green with minimal browning.