When we first started this business, we began asking winemakers and experts how to even measure oxidation in wine once it's been opened. Interestingly, we got different (and incomplete) answers from most of the folks we spoke with. The majority of preservation science in the wine industry is focused on what happens between harvest and bottling. We were interested in understanding EXACTLY what happens AFTER the wine is bottled. So we went to one of the World's leading experts in preservation, ETS Laboratories in Napa Valley, and started our own research in parallel.
Ultimately, we decided there are four main indicators you need to test for to be comprehensive about the impact of preservation: Dissolved Oxygen (DO), Acetaldehyde (start of acetic acid process), phenolics (the color change - the same browning you see when you slice an apple and leave it on the counter), and Sulfur Dioxide (SO2).
In parallel, we use wine experts to do taste testing to keep all the chemical testing honest.
Ultimately, we think that by piercing the closure and never removing the needle, using ultra-high purity argon, stainless steel tubing, and electronic solenoids to prevent oxygen from entering the system you get the best possible preservation. And luckily, the testing agrees.