“Fish oils are difficult to stabilize because they are highly unsaturated. However, a combination of dodecyl gallate (DG) and BHT substantially increases the storage life of herring oil stored at room temperature and at 40°C. Propyl gallate has been shown to retard the oxidation of fats in frozen Atlantic fish.”

According to the same source …

“Propyl gallate is effective in stabilizing soybean oil, cottonseed oil, palm oil, and hydrogenated vegetable oils. With refined oils, the addition of gallates or gallate-containing mixtures is beneficial in vegetable oils that are less highly unsaturated and have a fairly low natural tocopherol content such as peanut oil, coconut oil, palm oil, and olive oil. Addition of propyl gallate to crude oils results in higher oxidative stability of the oil after refining, bleaching, and deodorization, with better response to further antioxidant treatment. Butter prepared from acid cream is protected from peroxide formation by the use of octyl and dodecyl gallates at 0.01-0.03%, but the flavor stability is not improved. Dodecyl gallate at 0.01% and a mixture of 0.005% DG with 0.01% BHA were effective in suppressing the formation of peroxides in margarine. The mixture is effective at influencing the organoleptic quality of margarine. BHA retards the development of a ‘cardboard’ taste, and DG retards development of an ‘old’ taste. The gallates are effective in essential oils. A combination of 0.05% PG + 0.05% BHA + 0.05% BHT has been shown to be effective in the stabilization of orange oils, and 0.01% DG is a suitable antioxidant for lemon oil.”