DAGs (diacylglycerols) are fatty acids in olive oil. DAGs exist in two forms in olive oil – 1,2 chain diacylglycerols and 1,3 chain diacylglycerols.
DAGs break down over time, turning from 1,2 chains (the healthier and more desirable form) to 1,3 chains. The ratio of 1,2 DAGs to total DAGs is a really easy way to tell olive quality before pressing. It’s a great way of measuring olive oil freshness, too. Sometimes, a low ratio of 1,2 chain DAGs to total DAGs can indicate oxidized olive oil, or taste / smell defects.
Currently only the Australian Olive Association (AOA) measures DAGs and uses that level as one of the qualifiers for extra virgin olive oil. The percentage of 1,2 DAGs has to be at LEAST 35%. For an olive oil to qualify for ultra premium, the percentage of 1,2 DAGs has to be at least 90%.