For example, hydrogenation converts unsaturated fatty acids into saturated fatty acids. Dehydrogenation also converts saturated fats to unsaturated fats. Overall, saturated compounds are less reactive than unsaturated compounds. Epoxidized vegetable oils are formed by epoxidation of unsaturated fatty acids by reaction with peracids. Many bacteria use the anaerobic pathway for synthesizing unsaturated fatty acids. Most foods contain both unsaturated and saturated fats. Meat products contain both saturated and unsaturated fats. Most of the fatty acids are unsaturated. The oils from some algae have high levels of unsaturated fatty acids. Hydrogenation of unsaturated fatty acids is widely practiced. Various foods contain different proportions of saturated and unsaturated fat. Additives and polymers containing unsaturated bonds are highly prone to autoxidation. Hydrogenation is a useful means for converting unsaturated compounds into saturated derivatives. The molecule consists of a benzene ring attached to an unsaturated aldehyde. These are metal complexes that catalyze crosslinking of the unsaturated sites.