Up to 60% of yellowfin tuna steaks exported from Vietnam are treated with additives and gas to improve color and increase weight, according to seafood executives. The treatments include beet juice, paprika, and various additives, as well as carbon monoxide or a clear smoke. While these treatments are not illegal, they are not declared on labels. The executives recommend end users test for these ingredients. The treatment increases the tuna's value by 15-20% but misleads consumers into thinking they are purchasing a higher-grade product. The practice is becoming more common, especially among companies using lower-grade tuna.